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Pests in Hemp


Hemp (Cannabis sativa) is an emerging crop in California, with cultivars of industrial hemp legalized for production in the 2018 Farm Bill. By definition, industrial hemp may not contain more than 0.3% of the psychoactive compound THC in the parts of the plants sampled and regulated by the state. Hemp has various end uses ranging from fiber to flower buds to grain seed, however most growers in California are growing hemp for the cannabinoid CBD. Hemp cultivars can be dioecious or monoecious, but hemp cultivars grown for CBD have primarily been dioecious types (male and female flowers on separate plants,) with female plants grown for CBD production.


Pests in Hemp

Since hemp is a new commodity, pest challenges are still being observed and monitored. Certain agricultural pests have been observed on industrial hemp in California, but it is not yet known which cause significant crop damage or yield loss.

We know that tobacco budworm and corn earworm can cause severe flower damage. Webworms appear to cause damage to young stands when plants are small, but it is not clear whether hemp plants can grow out of it. Some other known agricultural insect pests have been observed on hemp, including leaf miners, spotted cucumber beetle, adult whitefly, lygus and mites. However, crop loss has not been confirmed for any of these species. While some of these pests can cause visible but minor damage to hemp plants (e.g. leaf miners), it is not clear if the damage is ever severe enough to affect crop yields. Many beneficial insects like dragonflies, native bees and honeybees have also been seen in these hemp fields.

Some diseases have also been observed on industrial hemp. Some, like beet curly top virus and Botrytis blight, appear to be problematic. Others like powdery mildew have been observed, but disease pressure was very mild and did not require treatment. Gopher damage to root systems has also been observed in drip-irrigated fields. More research is needed to identify important pests of hemp, determine which pests require management and develop IPM practices. In addition, it is unknown what pest pressure may build up in the landscape in the future as more and more acres of hemp are planted in the state.


Managing Pests in Hemp

Hemp is a highly regulated commodity, and regulations are changing to meet industry and environmental safety needs. Talk to your Agricultural Commissioner if you are interested in growing hemp. Pesticides that can be used in hemp are currently limited.

What determines if a pesticide can be used on hemp? The product must meet three requirements in order to be legal for application on hemp:

  • Exempt residue tolerance requirements.
  • Exempt from registration.
  • Use of the product would not be legally considered a use in conflict with the registered label.

What does this mean? Basically, a product that is labeled broadly enough to not be excluded from application to hemp can be applied. Generally, these tend to be “softer” chemicals; however, these products still come with risks, so care should be taken to follow the label and make safe and effective sprays.

Bee Safety

Although most industrial hemp plants are female, the seed feminization process is never 100% true, and males will be present in the field. Male hemp plants shed a lot of pollen, making them attractive to native bees and honeybees. Bee Safe practices should be followed when managing pests in hemp. See a previous article in the August/September issue of Organic Farmer on Protecting Bees in Hemp Production for more information.


Considerations When Thinking About Transitioning to Certified Organic Production


Farming is a difficult business. Farming organically is a bit more complicated than farming conventionally because it requires a different knowledge base and a different approach “between the ears” than conventional farming. Here are some thoughts about transitioning to certified organic production.

First of all, you should know that I’m biased toward many of the production practices that support organic production (cover cropping, use of compost, avoiding synthetic chemical pesticides and fertilizers, diverse crop rotations), because I’ve seen what good soil management and plant diversity above the soil line can do.

There are some basic considerations that farmers need to think about prior to transitioning to organic:

  • Market and market demand
  • Paperwork
  • Biological transition
  • Certified organic processing facilities (for meat, fruits, nuts or veggies)
  • Equipment
  • Commitment
  • Mindset


What’s Your Market?

There are a lot of conventional growers that have adopted some or all of the practices typically considered “organic” because these practices support nutrient and water cycling. So, if conventional growers are doing this, then the first question you should ask yourself is, “Why transition to certified organic production?”

If your market demands certified organic product, or if the most likely sector for growth in your market is certified organic, then you better start climbing that organic learning curve (attra.ncat.org is a good resource.) However, if you’re just wanting to “do the right thing” and aren’t necessarily interested in the organic price premiums, then perhaps certified organic isn’t the appropriate path for you and your farm.

You can experiment with planting cover crops or use of compost on a small block and observe the results. I would remind readers that most of our soils are in a degraded condition from years of tillage, compaction, chemical impacts and lack of organic matter, so it’s likely going to take at least a few years of managing your soils with respect, and as a complex ecology, to begin to bring the life back to them so they’re functioning properly.


“Paperwork” Transition

Certified organic production requires a three-year transition from the last application of a prohibited substance to the date of harvest of a certified organic product. Generally speaking, transitional product (i.e. not certified organic) doesn’t command any price premium. Plus, there’s the paperwork—each certifying agency has something called the Organic System Plan (OSP) that you need to fill out—it’s a record of all your inputs and many of your production practices.

You should also be prepared if you’re an organic grower in California to register with the State of California as an organic grower (and depending on the size of your farm’s gross sales, you’ll be able to pay for this privilege. To see how much, visit organic.cdfa.ca.gov/OrganicReg/Registration_Fee_2017.aspx.)

Annual inspections of your farm operation are also required by the certifying agency. And each certifying agency has a slightly different fee rate. For the last several years, USDA has provided each state’s department of agriculture some funds to defray the cost of organic certification to the grower. This is usually 75% of the cost of certification up to $750. These funds may or may not be available in the next growing season. Check with your state’s department of agriculture.

And on a slightly different note, USDA’s Natural Resources Conservation Service (NRCS) has a practice under their Environmental Quality Incentives Program (EQIP) called Conservation Activity Plan Supporting Organic Transition (CAPSOT 138), which will pay for a qualified consultant (known in NRCS-ese as a Technical Service Provider or TSP) to develop an organic conservation plan for your transitioning farm— nearly identical to an organic system plan. If you’re interested, ask your local NRCS Service Center about CAPSOT 138, and if they can recommend it.


Biological Transition

The biological transition of your ground generally takes a bit longer than three years. Certainly, your farm’s ecology will continue to evolve and revive as your expertise in organic practices evolves, but it also depends on how creative you are in your use of cover crops, compost and general management of the soil ecology and the above-ground ecology.

You can learn a lot from talking with experienced organic growers. You can speed up this biological transition by implementing the “five principles” of healthy soil management (see ATTRA’s publication on this at attra.ncat.org/product/manage-soil-for-water.)



There’s the “equipment curve” as well. You need to figure out what equipment you should have, but don’t have right now, to be an effective organic farmer; again, talking with an experienced organic farmer will help you avoid some of the larger mistakes transitioning growers might make. For example, cover crops are an increasingly popular way to improve soil health. One-hopper grain drills can be effective, but if you’re interested in planting a more diverse mix and different seeding rates, multi-hopper, no-till drills are available. Do you have equipment to manage a cover crop? Many farmers like flail mowers to handle heavy cover crops, but make sure you have an appropriate-sized tractor which has sufficient power to handle the flail mower.


Processing Facilities

A very important consideration is the location of processing facilities in relation to your farm’s location. Many certified organic products require certified organic processing facilities—this is especially important for nut crops, processing tomatoes, vegetables and leafy greens, and any meat or dairy products.

Transportation costs can quickly devour any organic price premiums that might accompany a product, so make sure you understand what certified organic processing facilities are available for your farm products and what the transport costs are.



The grey matter between your ears is perhaps the most important consideration. If you’ve been farming conventionally and relying on chemical fertilizers and pesticides for managing fertility and pests, be warned that organic farming is a different animal, and really a different way of farming.

Over-reliance on synthetic chemicals has allowed some farmers to mask a lot of unsustainable soil and pest management practices with increasing amounts of chemical inputs, but even that approach eventually becomes too costly and less and less effective.

Making a commitment to investing in your soils, just as you would invest in maintaining farm machinery or farm buildings, or training your farm’s staff, is an important commitment to make. But to invest in your soils, you need to understand what investments in your soil will provide the best return. You can begin by learning the basics of soil ecology and applying those aforementioned five principles whenever and wherever you can on your farm.


Mindset and Input Substitution

A word about input substitution, since you can make a small fortune with this approach, but you have to start with a large fortune. For growers transitioning to organic production from conventional practices, it may be tempting to simply substitute organic inputs for conventional inputs. This can be done, but you’ll likely go broke doing it, since organic inputs, including everything from organically acceptable commercial fertilizers to pesticides, can be pretty pricey. It’s much more practical to grow at least part of your nitrogen-using cover crops and to rely mostly on diverse rotations and creating beneficial habitats for pest control.

Changing approaches from reacting to problems by applying chemicals to a mindset of proactive ecosystem management is a radical shift in how to approach problems on your farm. It can be a steep learning curve as well. But many farmers I’ve spoken with about this claim that adopting a more ecologically-based approach to farming makes growing crops and livestock fun again and more interesting. The bottom line is: whether you decide to farm organically or not, all of us, including non-farmers, need to become better stewards of this planet, which, as far as we know, is the only place in the whole galaxy with life on it.

Rex Dufour has been working in sustainable and organic agriculture for over 40 years. He has completed the International Organic Inspectors Association (IOIA) training for organic inspectors, has a MSc in IPM from UC Riverside and is registered as a Technical Service Provider (TSP) with NRCS in CA and NV.


Additional Resources For Making the Organic Transition

To choose a USDA-accredited certification agency (ACA), look through the list of options on the National Organic Program (NOP) website: www.ams.usda.gov/AMSv1.0/nop  

“The Organic Certification Process” found within the Program Handbook, and in the ATTRA publication: Organic Certification Process:

How growers overcome the challenges of transitioning to organic: 

Transitioning to Organic Production, ATTRA News 2006:  

10 myths about transitioning to organic: 

Organic Certification of Farms and Businesses Producing Agricultural Products:

Non-GMO Dairy Transition Guide: 

Organic Transition Training: 

Thinking about transitioning to organic production:

Do the Numbers: Organic Grain Transition: 

MOSES Organic Farming Podcast 

Growing Organic Vegetables with Dry-Farming Practices


As climate change warms our planet, the ability to farm with less water is becoming increasingly imperative. Reduction of available summer water because of reduced snowmelt and drought is affecting food security. Farmers and researchers are working together to gain knowledge and come up with strategies for growing food with little or no irrigation.

The idea for dry-farming is simple: hold the water that falls during the rainy season in the soil so it’s available for plants that grow primarily during the dry summer. Dry-farming can be successful in areas that receive at least 20 inches of annual rainfall, such as the Pacific Northwest.

“There is a suite of practices to conserve water for our summer crop growth,” said Amy Garrett, Oregon State University (OSU) Extension Associate Professor of Practice, Small Farms Program.

The three main strategies for dry faming are:
1) Using a tillage system;
2) Protecting the soil surface; and 3) Choosing drought-resistant plant varieties.

These strategies work on land that has deep soil with good water retention. If soil is lacking such qualities, be it rocky or sandy, it can be amended with the addition of organic matter such as compost, growing cover crops and/or carefully managed livestock grazing, which recycles the cover crop into manure. The roots of dry-farmed vegetables seek moisture and grow deeper than irrigated crops. To look at the soil texture and moisture content at root level, take a 5- or 6-foot core sample.


Time the Tillage

Use careful timing. When you work the soil, do so in the early morning hours before the area is hit with direct sunlight and while there is still dew on the ground.

As far as seasonal timing of tillage, Garrett said, “We are starting as early as possible. We will typically flail mow our cover crop much earlier than irrigated farmers because as rain starts to slow down, the soils start to dry. We mow the cover crops in March or April when they are about knee high. We usually get a dry window sometime in the spring – as early as April, depending on soil type and microclimate, sometimes as late as the second week of May. We typically plant in May when there is still moisture in the soil. It’s important to put that seed in contact with moist soil.”


Cultivate the Soil Surface

Keep soil surfaces loose. It conserves moisture down at the root zone. Uncultivated soil tends to dry out and crack. Cracks in the soil open up and start drying out the deeper soil.

“Organic farmers are cultivating to manage their weeds,” Garrett said. “Some farmers in California cultivate five to six inches deep. It prevents this crusting and cracking from happening.”

As with any farming practice, improving the soil is key. “Anything we can do to improve soil quality is very important for dry-farming,” Garrett said.

Growers can also use organic mulches such as leaves, wood chips or straw. There are two drawbacks to these deep mulches: They cool the soil temperature. This could inhibit the germination of some direct-seeded crops such as melons and squash, in which case a transplant might work better. And the mulch may attract pests such as slugs, snails, mice and voles.

“We are looking into the benefits of deep mulch. A lot of people are experimenting,” Garrett said. “We’re just starting to analyze the data for leaf mulch.”


Plant Varieties

Some of the plants which have been grown successfully with dry-farming methods include drought-tolerant varieties of dry beans, melons, potatoes, squash – including winter squash and zucchini – flour corn and tomatoes.

A good source for dry farm seed is Seed rEvolution Now. Sundial Seed Company is another source. Both companies are located in California.

Garrett and others involved in Pacific NW growing trials have shown success with watermelon variety Christmas. “It’s one of our favorites,” Garrett said, adding that although some dry-farmed watermelons tend to get mealy or pithy, she’s never heard negative feedback about Christmas, at least not as far as taste. Oregon Coastal dry farm collaborators didn’t have enough hot, sunny summer days for Christmas to ripen in the Astoria, Ore. area. Other dry farm varieties that have proved themselves worthy in taste and performance are Dark Star zucchini and Stella Blue winter squash.

Early Girl tomato is grown with success by dry-farmers in Coastal Northern California. In the Oregon Willamette Valley, the summer humidity is too low, and Early Girl tends to get blossom end rot. Next summer, a dry-farm trial will happen in Oregon with 200 different varieties of tomatoes.

Since 2015, growers and researchers have been conducting variety trials. Included in the trials are a number of potatoes, several varieties of delicata winter squash, and maxima squash, which is a Hubbard type. Before COVID-19, the Dry-farming Collaborative (DFC) hosted farm tours along with taste tests with tomatoes and melons from both dry-farms and irrigated farms set out side by side. This year, the DFC hosted nine virtual farm tours.


Dry-Farm History and Research

Dry-farming is not a new way of farming, but rather a return to an old way that has been passed down from one farmer to the next. Only a small number of farmers experiment with dry-farming. Even fewer have extensive experience at it.

The farmers and researchers behind the DFC, OSU Extension Dry-Farm Project and Community Alliance with Family Farmers (CAFF) have expanded that knowledge. Their studies, led by Garrett, started in 2013 on Western Oregon and Northern California farms.

“We started out with case studies with farmers who had been doing this for a long time,” Garrett said. When she began her research into dry-farming, there wasn’t any information available through OSU, and no extension publications. “I’ve been kind of on a mission to raise awareness of the practices.”

During the drought of 2015, there were about 100 people who attended the dry-farm summer demonstration. “Many people had their wells run dry that year. There was a real concern with people about water,” Garrett said.


Getting Started

Dry-farming has definite benefits. Winter squash from dry-farming will store longer than its irrigated counterparts. Dry-farmed produce also has more flavor. Besides producing more flavorful produce, which could command a higher price, dry-farming works in harmony with nature by growing food in a more sustainable way than conventional, irrigated farming. In addition to using less water, dry-farming also uses less fertilizer and labor. There are fewer problems with annual weeds and, although tough perennials such as bindweed and Canadian thistle may persist. Dry-farming practices also protect carbon reserves in the soil.

The major downside to dry-farming is decreased yields. In some cases, yield reduction can be 25% to 50% lower when compared to irrigated crops.

“The best way to begin dry-farming is to start small, Garrett suggests. “Maybe just two or three rows.”

During the DFC winter meeting, “We all come together and talk about what worked and what didn’t,” Garrett said. The meeting will be virtual this year. “Opportunities are coming up. We’d like to find farmers who would like to join us, gather some ideas of things they’d like to try.”

The DFC also has a Facebook group. “We’re specific northwest centric,” Garrett said, “but we have people from all over who are interested in dry-farming.”
Check out the OSU Small Farms, Dry-farming website at:

Interest in Victory Gardens on the Rise During COVID-19 Pandemic


A century-old food movement in the United States is making a come-back during the COVID-19 pandemic. This movement, known by some formerly as Liberty Gardens, can be traced all the way back to World War I. Today they are called Victory Gardens, and interest for them is growing fast.

Victory Gardens are home/public gardens introduced typically during times of national turmoil. There are multiple reasons people plant Victory Gardens during difficult times, but among the end results of these gardens are educating people, young and old, about a connection to agriculture, and bringing them together.

Rich History

Dr. Rose Hayden-Smith, Emeritus, UC ANR, is an expert on Victory Gardens and authored Sowing the Seeds of Victory: American Gardening Programs of WWI about the history of home gardens in war-time America. Hayden-Smith is enthusiastic about the history and idea of Victory Gardens, and believes they can “lead us places.”

“What most people don’t realize about victory gardens is we all think about them about being the iconic home front mobilization program of World War II; they actually came first in World War I,” Hayden-Smith said. “There was one program part of this larger movement called the US War Garden Army. There was a large group of people in this movement that were concerned that their kids weren’t aware of the connection between agriculture and the public.”

Gardening was introduced as part of a rich curriculum to educate children and was viewed as an essential effort for national security,” Hayden-Smith continued. “There were concerns about morale during this time, and people thought gardening would give the country a national purpose.”

Public and government agencies came together for this movement in a way that is not seen as much today. With the success of these programs, people placed great meaning in the gardens, according to Hayden-Smith, pushing public message support in immense ways such as creating “poster art”.

“I think Instagram is the sort of poster art today that was prevalent during World War I and World War II, and has been a huge drive for interest in Victory Gardens today,” Hayden-Smith said. “I don’t think we’re going to see a decline in interest.”



Similar to today, there was a widespread pandemic during World War I when Victory Gardens made their first documented appearance. During this time, certain access to food was limited due to mandates from the pandemic as well as the effect it had on businesses. This caused concerns about food security, disruptions in food supply, civil unrest and concerns about being disconnected from the source of food.

The most beneficial aspect of Victory Gardens is their ability to give people a sense of food security and promote the important idea of food sovereignty. Since Victory Gardens enable virtually anyone to grow their own food in a sustainable fashion and have easier access to food during difficult times, many are starting to take to the idea of these gardens being a permanent staple after the pandemic.

“I think it’s going to take off like a rocket,” Hayden-Smith said. “While this pandemic is the worst, it’s helping people prioritize what’s important going forward. I think that people get it about the food now and why there’s been a crisis for a while. If you’d told me a year ago that food sovereignty issues would have been leading national news right now, I wouldn’t believe you, and I think that says something.”

Another beneficial aspect of Victory Gardens is the feeling of community they can create. During difficult times, bringing people together is important, especially when it comes to food choices and sources. Many that participate in Victory Garden movements do it for food security, but others do it for the sense of community and to help spread education about sustainable farming and agriculture.

“Our relationship between people and the landforms an alliance, and I think people don’t think about that enough,” Hayden-Smith said. “Community is one of the most important aspects of Victory Gardens. I think the conversion of prime public space to service the nation with these gardens is amazing. Prioritizing this is important, and people learn from each other.”

Now v. Then

Physically, the makeup of Victory Gardens is a bit different than how they were last century. Today, they consist more of container gardening with root vegetables and seasonal planting, according to Hayden-Smith. In terms of their purpose, though, they are more or less the same.

Having a close or direct connection to food sources and information is a driving factor for establishing Victory Gardens. Other reasons for gardening during today’s pandemic, Hayden Smith said, include wanting variety in diets (fresher and healthier ingredients), being closer to the land and becoming informed about sustainable agriculture. As was mentioned above, this reasoning is similar to the reasoning during the World Wars if not the same.

Victory Gardens are ultimately an under-researched topic in the world of organic farming and sustainable agriculture, but they have still proved to be widely beneficial over the last century. People like Hayden-Smith have been working diligently to prove this, helping people learn about the land and agriculture and integrate food sovereignty practices into their lives.

For more information about Victory Gardens, visit rosehaydensmith.com.

UC’s Houston Wilson Leads New Organic Agriculture Institute


In recent decades, as California’s organic agriculture industry has grown, education and research on specific practices for organic agriculture has in some cases lagged behind that growth in acreage. The University of California (UC) now has a specific institute dedicated to organic farming in the newly created UC Organic Agriculture Institute (OAI). The OAI is housed within the UC Division of Agriculture and Natural Resources (UC ANR) and was established with endowments from Clif Bar and UC President Janet Napolitano. These endowments will provide the initial annual funds to support the efforts of the OAI, which will be focused on the development of research and extension programs for organic production of tree nuts, tree fruit, raisins and rice.

These efforts will be led by newly appointed Director Houston Wilson, a UC Riverside agricultural entomologist and Cooperative Extension Specialist based at the UC Kearney Agricultural Research and Extension Center in Parlier.

Resource for Organic Agriculture

One of the first steps for Wilson and the OAI will be to conduct a statewide needs assessment to determine the most critical research areas to focus their efforts on.

“Through a series of surveys, focus groups, cost studies and analysis of existing data on organic crop production, we will characterize the current status and needs of organic agriculture in California,” Wilson said.

This assessment, Wilson said, will also help the OAI identify relevant expertise within the UC system to develop multi-disciplinary research teams to address specific problems in organic agriculture. The OAI will also organize and facilitate regional crop-specific extension meetings, as well as an annual organic agriculture conference, to bring together growers, researchers, extension personnel and other industry stakeholders focused on tree nuts, tree fruit, raisins and rice.

“Some other potential activities include a small-grants program to help launch new projects and research fellowships for undergraduate students to gain experience in organic agriculture science,” Wilson said.

Wilson is looking to quickly establish the OAI as a center point of the organic agriculture industry, and networking for the purpose of collaboration and activity development.

“We are currently reaching out to build relationships with the many organizations and stakeholders in the organic agriculture community across California, as well as with growers, commodity boards and relevant programs within the UC and CSU system,” Wilson said. “As we design the OAI, we are building in multiple ways for these stakeholders to interact with and provide input on our programmatic activities (such as establishing an Advisory Committee.)”

Experience in Organics

While Wilson was only recently appointed as the OAI’s new Director, he is no stranger to organic farming practices. As Principal Investigator (PI) of the Wilson Lab at the Kearney Ag. Center, much of Wilson’s vineyard and orchard research has applications in organic agriculture.

“Many of the pest management practices we focus on do fall under the National Organic Program, such as crop sanitation, biological control, mating disruption, cover crops, improved trapping methods and sterile insect technique—but many of these practices are equally important for conventional and organic growers alike,” Wilson said.

While the goals of Wilson’s research and extension program are often relevant to the OAI, he considers these focused entomology activities separate from his role within the OAI, which will encompass many additional disciplines and target crops. As Director of the OAI, Wilson said, his primary role is not as a researcher, but rather to facilitate the development of a multi-disciplinary research and extension program for organic agriculture.

“Research and extension needs across our focal crops will likely encompass multiple disciplines, including pathology, weed management, crop nutrition, soils, irrigation and entomology,” Wilson said. “In this way, as Director, my job is to bring together the most relevant experts to address issues in these different areas.”

Even though Wilson has come into contact with many organic growers over the course of his career, he has never done so in such a targeted manner as he is now as Director of the OAI, he said. Nonetheless, he is still looking forward to entering an organic setting.

“I’m looking forward to meeting and working with new growers, organizations and other stakeholders,” Wilson said. “I previously never had a mandate to focus on organic, but now have the opportunity to fully delve into this sector of agriculture.

“California has always been a leader in organic agriculture, and as such there is a rich history here that involves a lot of great people who have worked for decades to develop, define and promote organic agriculture,” Wilson continued. “In this way, it is an honor to have been selected for the inaugural Directorship of the OAI and to now have the opportunity to interact with and learn from all of these different folks.”

Organic Agriculture Will Prosper

While California is already a prospering organic powerhouse, with 3,000 certified organic farms growing crops on 21% of all U.S. certified organic land, there is much more room for growth. Certified organic products are in demand and the UC OAI will provide guidance not only to currently certified organic growers, but also to farmers looking to make the switch from conventional to organic agriculture.

“We will likely organize annual and/or regional extension meetings for our focal crops,” Wilson said. “These will provide a training opportunity for growers that are currently certified, as well as those that are interested in transitioning to organic.

“We may even schedule events that specifically target growers that are looking to transition,” Wilson continued. “There is some grant funding available for projects that target transitioning growers, so that might be a good place to find financial support for these efforts.”

Managing Weeds with Propane-Powered Heat Technology

Among both organic and traditional producers, an increasing number of farmers are seeking greener alternatives for weed and pest management. Heat treatment technologies like propane-powered flame weeding systems and Thermaculture provide a unique alternative and solution, offering many benefits over conventional herbicides and mechanical weed removal advantages.

Flame Weeding

Propane flame weeding offers a highly efficient and organic alternative to herbicides or tedious manual labor. According to field studies funded by the Propane Education and Research Council, flame weeding is up to 90% effective against weeds by using intense heat to rupture plant cells, causing the weeds to wither and die. Approved for certified organic farming operations, propane flame weeding also avoids the disruption of essential soil nutrients, which commonly occurs with cultivation and tillage weed control methods.

The flame weeding system is available as a handheld torch or as torches and burners connected to a tool bar with the propane tank mounted onto the back of a tractor. Either way, the process is quick and easy, leading to improved efficiency for farmers.

Additionally, flame weed control is a flexible solution that can be used in a variety of weather conditions. Flame weeding can be used to weed fields early before seedlings have started to come up or late (after harvest) to prepare for the next spring. Farmers know that timeliness is critical for a successful operation and, fortunately, propane systems can help them stay on track, even when field conditions aren’t ideal or during seasons of wet or erratic weather.

In 2010, Certified Organic Farmer Larry Stanislav participated in a research study with farming partner Elizabeth Sarno, who was an extension educator and organic research project coordinator for the University of Nebraska. The Propane Council worked with university researchers to fund a study aimed at increasing the efficiency of propane flame weeding systems in organic cropping systems.

Results from this study showed that a hooded propane system increased heat concentration on weeds while reducing fuel use, which improved the effectiveness and efficiency of propane flame weeding. Study participants reported weed control levels as high as 95%. The research led to the development of a training manual for the practice in corn and soybeans and the commercialization of a four-row banded/full propane flame weed control system marketed under the name Agricultural Flaming Innovations. Since this study, there have been several advancements to the technology, making propane flame weeding systems even more efficient and beneficial than ever before.

For Certified Organic Farmers like Stanislav, flame weeding systems have become an essential tool for weed control. He estimates that for his 50-acre plot of organic corn, it saves him at least 30 hours of labor time compared to traditional weed control techniques.
“Using a propane flame unit to control weeds also eliminates disturbance of the soil,” said Stanislav. “You might spend more on the equipment at the outset, but in the long run, soil health and increased yield are big benefits.”

While propane flame weeding has been around for years, new innovative models make the use of heat treatments for weed removal more effective than ever. Research supported by the Propane Education & Research Council has shown that weed flaming provides approximately 95% effectiveness in weed control for a variety of crops. Propane is a clean, non-toxic, non-poisonous fuel that won’t contaminate nearby crops, soil or groundwater. Plus, it’s an approved clean fuel under the Clean Air Act of 1990 and produces fewer greenhouse gas emissions than other fuels such as diesel and gasoline.


A new technology that initially delivered dividends in the highly scrutinized world of wine making is now available for a whole new segment of growers that want a sustainable, chemical-free alternative to controlling insect and fungal infestations and weeds. This emerging practice is called Thermaculture, a propane powered heat application pioneered by Agrothermal Systems.

“We thought to ourselves, ‘what if we could give growers heat on demand, which is basically the sun on demand’,” said Drew Sanders, CEO of Agrothermal Systems. “We’ve been finding niche areas where too much heat, too little heat or too much moisture is a problem, and coming in to help growers.”

Thermaculture heat protocols work with Mother Nature to raise the natural defense system of plants, interrupting most insect and fungal development. It also helps fight disease and crop damage by drying out crops after it rains. When applied in vineyards, it’s proven to increase fruit set and yield. The heat raises the plant temperature to the levels needed for optimal fruit set and growth, even in cold, wet weather. Users on average see a 24% increase in fruit set and 20% improvement in yields, according to Agrothermal.

In studies conducted in 2017, Agrothermal Systems saw fungicide use reduced by at least 50% during several wine grape trials. Since then, this heat technology has expanded to show its benefits for general produce and specialty row crops, too. When used for produce and specialty row crops, this method helps to fight disease and crop damage by drying out crops after rainfall.

According to a study by Caltec Ag of Modesto, Calif., Thermaculture heat treatments provided several benefits including cost. The propane used per acre to produce the heat was about six gallons per acre, for a price of roughly $10.

Michael Newland is director of agriculture business development for the Propane Education & Research Council. He can be reached at michael.newland@propane.com.

Considering Zinc Needs for Organic Production


Trace elements, including zinc and several other micronutrients, have become a topic receiving much greater emphasis over the last few decades. These nutrients, though needed in much smaller amounts than the primary elements like nitrogen, phosphorous and potassium, are nevertheless essential for crop growth, soil and plant health, and for the production of nutrient-dense food and feedstuff.

One comparison that farmers and growers can appreciate is that trace elements in the soil function somewhat like spark plugs in a motor. Though only needed in small amounts, they are essential as catalysts or activators for many plant processes. They are necessary for top performance from any soil or plants being grown there.

The list of micronutrients considered as essential may vary depending on the crop and/or soil being considered. Those most generally included on soil tests are boron, iron, manganese, copper and zinc. Molybdenum (especially for legumes) and cobalt (especially for livestock and soil microorganisms) should also be considered where they could be deficient enough to cause problems, but the costs are such that for many growers, only key areas are initially tested and treated accordingly. Chlorides can also be tested for growers who may have a problem with salty water or salt deposits on their land. Some also test for silicon and selenium, but the levels and needs are not as well understood and defined for these elements as for those aforementioned above.

Zinc in Soil

Zinc is likely the most accepted and most often applied of all the trace elements. It is perhaps the least controversial micronutrient of all those mentioned above. Zinc is widely applied and considered as most necessary on crops like corn, rice and pecans. For example, adequate zinc is needed to determine the size of the ear (i.e. the number of kernels) of corn during the early growth stages (V4 and V5). But all crops respond well to zinc when it is correctly supplied.

The weight of the total amount of elemental zinc per acre found in the aerobic zone of the soil (which is the depth to which a wooden fence post rots, generally 6.5 to 7 inches deep) can be from 20 pounds to 600 pounds per acre. But most of that zinc is not in a form the plants growing can take up and utilize. Most of the zinc in the soil is “tied up” or “locked up” and unavailable to be taken up and used by the growing crop.

What needs to be determined is how much zinc is present in each soil in a form that is available for plant uptake and use. The total amount of zinc in all forms, whether available for plant use or not, can be determined by a soil test. But the determination most needed is the amount of zinc in the proper form for plants to take up and use which is considered as the amount of plant-available zinc in each soil. Of the total zinc contained in each soil, a minimum of 12 pounds per acre is needed to avoid zinc deficiency in a growing crop.

There are those who grow organically that may dismiss any need for adding zinc or other trace elements to the soil as they expect such materials will be provided by the use of compost or other natural methods. Zinc from compost and manures is useful, but that amount is seldom if ever enough to increase measurable levels in a zinc-deficient soil. Perhaps this is due to the bio-availability of zinc from composted materials which allows more immediate uptake by plants.

Using bone meal can increase measurable zinc levels in the soil over time. Growers who have applied large amounts of bone meal may have sufficient, or even excessive, levels of zinc in the soil. In fact, it can build the zinc levels too high when used in excess which then affects phosphate availability and, if high enough, it can hurt availability of other nutrients such as magnesium, manganese and copper as well.

But what happens when such is not the case and zinc levels are actually deficient in the soil? What difference does it make? And even if it does matter, how can growers know when the soil has too little, too much or just the right amount?

Deficiencies and Availability

Using soil tests is one method that can help evaluate whether zinc levels in the soil are adequate, but far too many who grow organically are just not sure whether to place their trust in such methods or not.

There is an old saying with which many organic growers can identify – “Study nature, not books!” So, perhaps looking at what happens in the field can provide some initial directions that can then be correlated back to what a detailed soil analysis can or perhaps cannot actually show in such cases. A better understanding about zinc and how to use it can help growers determine when whatever methods being used should be considered as sufficient or insufficient for supplying the needs of crops grown on that soil.

Zinc is one of the easiest trace elements to build. Even in soils that are extremely deficient it can be sufficiently applied to adequately reach required minimum levels for the very next crop. It is generally the most economical to correct and maintain of all those trace elements.

It is well-known that zinc is commonly lacking in plants grown in soils that have excessive phosphate levels. This is one of the first big hurdles that organic growers who use large amounts of compost must eventually face. Use of too much compost will at some time in the future ultimately result in too much available phosphate in the soil. Once that happens, zinc availability suffers. This can still be the case in soils with adequate to high or even excessive levels of zinc.

Too much phosphate in the soil can affect zinc availability to the point of reducing water uptake needed by the plants growing there. Zinc is essential for moisture absorption by plants. When soils have enough zinc for correct moisture absorption, they generally have enough zinc for performing the other needed functions in the crop as well.

Deficiencies tend to be greater in lower exchange capacity soils such as sands or very coarse clays. Deficiency symptoms are expected most in new growth. Smaller leaves or leaves that wilt very soon after watering for example indicate a possible serious need for zinc. An accurate soil test can be used to determine when zinc is needed and in what amounts.

Soil Needs and Testing

What level of zinc is needed in the soil? Always keep in mind that there are several different ways to test for, measure and report zinc levels for the soil, and most tests will read far lower than the figures from the testing that actually reflects the need for zinc on a pound for pound basis. So, do not try to universally apply the test numbers from one laboratory to other soil tests to determine if zinc is deficient or not. If so, you could wind up applying far more zinc than is needed to the soil.

On the other hand, there are soil tests that some soil laboratories use that consider zinc as adequate when tests that measure zinc needs on a pound for pound basis show as still too deficient. How do growers know which one is right? How can that be best determined? First judge by how crops respond and then by measuring what levels are needed in the soil to provide the proper response.

For best results, match phosphate and zinc needs for each different soil. On soils with very low phosphate levels, plant-available zinc measured as needed on a pound for pound basis should be at the minimum requirement of 12 pounds per acre or 6 ppm. When phosphate reaches excellent, zinc should be 20 pounds per acre or 10 ppm, and if excessive, then 40 pounds per acre or 20 ppm. Just remember, when phosphate is excessive enough so as to affect zinc availability, it will require more water to produce the same potential crop yield.

On the other hand, extremely excessive zinc can reduce phosphate availability and can cause other problems that may not always be as obvious as the actual example being shown here.

Figure 1 shows an example. The weed growing there is generally not that common in fields in the area. It is field pennycress that appears to have been planted right in the row where the corn was planted last year. The same weed is growing in the middles, but notice in the photo titled Figure 2 picture that it is not nearly as mature and vigorous as those growing in the old cornrows.

Samples of both the soil and the plants were taken in the rows and the middles. The plants growing in the row had extremely high concentrations of zinc. The same extreme zinc levels were also shown to be true for that soil. In fact, the rows had extremely excessive zinc levels right where the weeds were growing best, but out in the middles, the soil test showed zinc levels were quite deficient. The type of zinc used had built it up to excessive levels right under the row where it was applied but had no influence on levels even inches away.

This helps to illustrate what can happen when too much of any nutrient is applied to a soil directly under the seed. How much does it require before the availability of other nutrients (namely phosphate in regard to excessive zinc) starts to be reduced? Plants send their roots directly to the richest source of nutrients as fast as they can do so. This has been shown to be true not only for banded fertilizers but even for small clumps of manure or compost as well. These sources will quickly attract plant roots. Could this be why some farmers who band their zinc believe they need to add more phosphate when the soil test levels show to be far more than adequate for growing the crop?

Building up the availability of zinc in a soil can be accomplished with one broadcast application. The proper forms of zinc (some forms are soil feeders while others are only plant feeders) are quickly available and easy to build in a soil when those needs are correctly measured and the correct form is applied. Even in severe cases of deficiency, provided there is sufficient calcium there to get the zinc into the plant (a minimum of 60% base saturation on the test we use), zinc that has been taken up in sufficient amounts for the crop, even grass and trees, can make a difference in the plants growing there in three days.

One client who was growing turf grass reported that the grass just could not get enough water. Even though the soil was still wet from the previous irrigation, the grass would begin to wilt and only applying additional irrigation water would solve the problem. They had a severe zinc deficiency.

Based on the need shown by doing a soil test, the required amount of the correct form of zinc was applied as a broadcast application to sufficiently build up the level in the soil. The problem was solved in just three days! After that, normal irrigation was sufficient to grow excellent grass. The soil had everything else it needed, but the lack of supplying enough zinc was the problem.

The effectiveness of the various forms of zinc can be determined when the testing being done reflects the amount that is applied to the soil on a pound for pound basis. When this is the case, growers can soon see which products are most effective for use on the crops they are growing.

But too many forget that it takes two years to measure the full effects of a zinc application on any soil. The efficiency of zinc also depends on an adequate supply of calcium which is not accurately determined by the pH of the soil. Many soils have a “good” pH but lack calcium in sufficient amounts to take up zinc and other trace elements properly. The true determination of calcium needed is whether the soil in question has a base saturation of 60% calcium or higher. The lower the calcium saturation drops below 60%, the harder it is for plants to adequately respond, even when zinc levels are sufficient.

Zinc Sources

There are several different sources of zinc available for use by organic farmers. Those materials should first be divided into one of two classifications. Is the zinc being applied as a soil feeder or a plant feeder? If the form of zinc is a plant feeder, applying what should normally be considered as sufficient amounts to build up soil levels will not be successful. On the other hand, those forms of zinc that work as soil feeders should show zinc levels are being built on a pound for pound basis at the end of two years.

Rice is an excellent crop to use as a test to show the accuracy of a soil test and whether the zinc being used is a good soil feeder or only a plant feeder. When there is less than 12 pounds (6 ppm) per acre of zinc in a soil used for growing rice, the tips of the rice blades will begin to die. The problem is called “bronzing of the tip”, and on zinc-deficient fields it generally shows up by the time the first top-dress of nitrogen is needed by the rice crop.

If the soil test shows the soil has 6 pounds (3 ppm) of actual zinc, then it needs another 6 pounds to reach the minimum required 12 pounds per acre. This means the soil needs the equivalent of almost 17 pounds per acre of a standard 36% zinc sulfate to correct the problem via the soil.

There are other forms of zinc that cost less that can be applied and still eliminate this same problem in a rice crop. Farmers can apply the same amount of zinc using 36% zinc oxysulfate which costs less and solves the problem. An equivalent amount of foliar zinc chelate or even a plant extracted foliar zinc will do the same.

But all of these products that substitute for zinc sulfate are designed to be used as plant feeders. They supply just enough zinc to solve the problem, but the next time you grow rice there or if you grow rice there again the next year, you have to use the same amount again to solve the same old problem – year, after year, after year.

But a true zinc sulfate is a soil feeder. Supplying a sufficient amount of zinc to reach 12 pounds per acre just once when using it will solve the problem with only that one application for five to seven years before needing another maintenance application – generally about another 10 pounds per acre of 36% zinc sulfate. All soils need to at least maintain the 12 pounds of zinc per acre which is the actual minimum amount needed for all crops. Provided the soil has the minimum amount of needed phosphate and adequate calcium, the proper form of zinc will work there very well.

Just how important is it to maintain this minimum 12 pounds per acre level of zinc? Perhaps the response of soybeans to adequate zinc will prove to be a good example. When sufficient amounts of all the other nutrients are provided and zinc levels show to be 10 pounds (5 ppm) per acre rather than the required 12 (6 ppm), then supplying 10 pounds per acre of a true 36% zinc sulfate will increase the soybean yield by 10 bushels per acre. And if you use a true zinc sulfate (a soil feeder, not a plant feeder), that benefit will last about 5 to 7 years or even longer if you are using sufficient amounts of compost.

Once out of the aerobic zone, available zinc tends to decrease more and more as you probe deeper into that soil. Zinc, like phosphate, will always be most available in the aerobic zone. This is true unless the top soil in the field has been eroded away by wind or water, or when it has been removed and not put back where land has been graded or scraped for leveling. Another example is when the top soil is removed with the crop such as in harvesting turf grass.

All materials should be applied as a broadcast application that tend to help build up nutrient levels in the soil. For example, 36% zinc sulfate will increase zinc levels pound for pound when applied on the soil. Once applied it will remain there in the soil in an available form until utilized by the crop or the biological activity that supports crop growth. Such products are considered as soil feeders. They do not tie up easily once applied to the soil where proper treatment of the soil is practiced.

On the other hand, 36% zinc oxysulfate tends to be a plant feeder. When it is applied at the same rate as 36% zinc sulfate, much of the time the zinc level in the soil does not change at all. It is made by predominantly using a cheaper form of zinc, zinc oxide, in combination with a proportionately smaller amount of zinc sulfate. Some of these products do serve as soil feeders. It appears that when the zinc oxide is completely pulverized and then combined with zinc sulfate, it will help build zinc levels in the soil. If the product will build available zinc levels as measured by a reliable soil test on a pound for pound basis, then it is considered as a true soil feeder for building and maintaining needed zinc levels for soil and crop needs.

Effects of pH

There are far too many false concerns about the effects of high pH on zinc availability. It is true that as the pH of a soil goes up, the available zinc levels in that soil will be reduced accordingly. But the effects of the pH increase are only a concern for the zinc that is already there.

For example, on soils with a pH of 8.0, if the plant-available zinc is below the needed minimum of 12 pounds per acre, then applying an appropriate amount of 36% zinc sulfate will build the level of plant-available zinc right back to the prescribed amount. With a soil test that truly measures plant-available zinc and the use of a true zinc soil feeder fertilizer product such as 36% zinc sulfate, the levels will come right back to where they need to be in two years’ time. On high pH soils, it happens all the time.

If this does not work on a particular soil, there is generally a good common-sense reason as to why. First, was it truly a soil feeder form of zinc, or could it possibly have been a plant feeder form instead? Second, did the soil test used truly measure and express the zinc level on a pound for pound basis or is some other test being substituted to help make it “quicker and cheaper” to perform?

In addition, keep in mind that an excessive amount of phosphate can tie up available zinc in the soil. So can using extremely high rates of nitrogen or applying excessive amounts of manure or compost. The only way to know for sure is to find a test you can count on to measure what is actually there in the form needed to supply the crop.

On soils that receive limestone applications, the availability of micronutrients will be reduced. This is of greatest concern when the soil has borderline or deficient trace element levels. This includes zinc levels that do not remain above 12 pounds of plant-available zinc per acre once enough time has passed and the lime has had time to completely react with the other nutrients in that soil. This can require as much as three years to see the full effects on the nutrient levels in that soil, including plant-available zinc. If the field has borderline zinc levels and none is added, it may be the first, second or third crop before the zinc drops to a deficient level. The only way to know for sure is to monitor the plant-available zinc before each crop is grown.

This then should bring up one more consideration when it comes to assuring the soil in each field has enough zinc. Once you have a test that can measure and report what the zinc level should be, how often should you test that field to assure the zinc and everything that can affect it is still in order? Some will advise testing the soil every three or four years to “save money” – REALLY?

As one farmer stated after learning the value of using soil tests to maximize nutrient content and encourage better yields, “A soil test costs less than one small bale of hay per acre, and I can lose a lot more than that if just one nutrient is not properly supplied for growing the next crop.”

Start small, but prove it for yourself – you must, as most soil tests are used to sell you something, not teach you something.

For those who may be interested, boron is the next micronutrient to be discussed in this series of articles on trace elements and their usefulness for organic growth.

Neal Kinsey is the owner and President of Kinsey Agricultural Services. Please call 573 683-3880 or see www.kinseyag.com for more information.


Overview of Biostimulants in Permanent Crops


One of the few things people can agree on about biostimulants is that they are difficult to define. The Biological Products Industry Alliance (BPIA) suggests:

“Plant biostimulants contain substance(s) and/or micro-organisms whose function when applied to plants or the rhizosphere is to stimulate natural processes to enhance/benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress and crop quality.”

What is a Biostimulant?

Biostimulants are hard to define as there are many different substances and microorganismal inoculants used in their production. It is also difficult to quantify the mechanisms for how biostimulants work and ultimately provide benefits to crop health and quality.

Commercial products may have several different ingredients such as amino acids, micronutrients and beneficial microbes. Biostimulant research has focused on many different products, tested on different crop species, in different environments. Some studies have shown evidence for biostimulants reducing the impact of stressors on plants, but this has not been universal.

A review paper by Povero et al. shows examples of reported biostimulant effects including enhanced fruit set, size, quality, root development, plant growth, water and nutrient uptake, stress mitigation and soil improvements. Another review discussed 26 different biostimulant studies conducted on fruit trees (Tanou et al. 2017). The categories of products (used individually or sometimes in combination) included protein hydrolysates, seaweed extracts, humic substances, leaf/pollen/yeast extracts, amino acid chelate and Leonardite extract. This broad range of products and effects can make it difficult to decide whether anyone biostimulant will be helpful for a particular situation.

Biostimulants are not currently regulated in the United States as they are classified differently from fertilizers and pesticides. However, it is possible that they will be regulated in the future. In spring 2019, the EPA released for public comment a “Draft Guidance for Plant Regulators, Including Plant Biostimulants”. There has not been a new update since then, but it is possible that some biostimulants, which have the properties of plant growth regulators, will become subject to the Federal Insecticide, Fungicide and Rodenticide Act, which will require registration and labeling. If this happens, it may change what products will be available, but will also provide some oversight to the industry.

Biostimulants can be applied through irrigation systems to aid in specific functions such as stress tolerance or fruit quality. (photo by Marni Katz.)

How Biostimulants Function

Biostimulants have a different function than fertilizers. Fertilizers are used to add macro- and micro-nutrients to the crop, which improves crop growth. Like fertilizers, biostimulants can be applied either foliarly or through the irrigation system and may contain some low levels of nutrients. However, the addition of nutrients is not their main purpose. They are more likely to be used to add biological products such as microbial, acids, and hormones to the plant and soil to aid in specific functions such as stress tolerance or fruit quality.

To date, most of the studies that have been done on biostimulants have been on vegetable crops, possibly because they can be completed more quickly than permanent crops. Also, permanent crops contain reserves of nutrients in their woody structures, which could become a confounding factor in their evaluation (Soppelsa et al. 2018). Even when all applied substances have been controlled, permanent plant tissue can release nutrients to assist in plant growth in ways that are difficult to account for. This makes it more challenging to determine if an observed effect is due to the applied biostimulant or not.

Trial Results

As mentioned earlier, many biostimulant products contain multiple components, which can make identifying the causal agent difficult. For example, in a potted almond trial, Saa et al. applied two different products to two-year-old trees. One product was from seaweed extracts, and one was from the microbial fermentation of a proprietary mix of organic cereal grains. The seaweed extract product also contained amino acids, glycosides, betaines and vitamins. This study was especially interested in potassium, and it compared both biostimulant treatments to a foliar potassium treatment and a control. All four treatments were applied to trees that had been fertilized with either adequate or low levels of potassium, with all other nutrients controlled for. The results showed that both biostimulant treatments increased the shoot length and biomass when potassium levels were adequate, but only the seaweed-based treatment was also effective in the low potassium treatment. That would seem to indicate that potassium was a limiting factor and that the seaweed-based product was able to resolve that, but the microbial fermentation product contained even higher levels of potassium, so the actual mechanism is still unclear (Saa et al. 2015).

Another biostimulant trial done on young almond trees in Spain compared the combined application of two biostimulants to control treatment in three almond cultivars with two irrigation treatments (Gordillo et al. 2019). Each of the biostimulants had multiple components. One had a combination of aerobic and anaerobic bacteria. The other was extracted from shrimp meal through a microbial fermentation process and contained amino acids, nitrogen and trace levels of other nutrients. Each of the three cultivars had a slightly different response to the treatments. In biostimulant-treated ‘Guara’ trees, there was a higher leaf water potential (less stress) than in the control under both irrigation regimes. The treated trees also had higher yields in both irrigation regimes. Biostimulant-treated ‘Lauranne’ and ‘Marta’ trees had higher stomatal conductance than control during vegetative stages, and ‘Lauranne’ trees’ stomatal conductance was also higher during kernel fill. This study shows that even within a particular species, biostimulants may have different effects. However, this study only had one season of data collection, so it is unclear whether the results can be replicated.

Seaweeds are one category of biostimulants that have shown a lot of promise. In a review article on seaweed biostimulants, Battacharyya et al. referenced over 50 seaweed studies that have been conducted on vegetable and fruit crops as well as ornamental crops and turf grasses. The reported effects included increased germination, increased yield and increased uptake of various nutrients. In a different study of brown seaweed, Ascophyllum nodosum, researchers found that skin total anthocyanins at harvest were significantly higher in wine grapes treated with the biostimulant than in the untreated control (Frioni et al. 2018). The first year of the study was conducted in Italy with two different concentrations of the seaweed extract on Sangiovese grapes. The second year of the study was conducted in Michigan with one concentration of the biostimulant applied to two grape cultivars: Pinot Noir and Cabernet Franc. The goal was to test out the seaweed extract in different climates and in different cultivars. The anthocyanin level was the one factor that increased in all seaweed biostimulant treatments in all cultivars in both locations, indicating some consistency.

Although there is anecdotal support for the use of some biostimulants, more replicated research trials are needed to demonstrate which products are effective for which crops in which situations. If the mechanism for how the products work can be defined, it will make it easier to decide when and how they should be used. There are many different products on the market, and if growers are interested in trying them out, they should contact their local farm advisors, PCAs or CCAs to help them set up a demonstration trial. Products should be chosen based on the needs of the crop, and compared to an untreated control. For best results, conduct trials over multiple seasons.

Enhanced fruit set is among the benefits found in some studies. (photo courtesy USDA NRCS.)


Battacharyya, D., Babgohari, M.Z., Rathor, P. and Prithiviraj, B., 2015. Seaweed extracts as biostimulants in horticulture. Scientia Horticulturae, 196, 39-48.

Frioni, T., Sabbatini, P., Tombesi, S., Norrie, J., Poni, S., Gatti, M. and Palliotti, A., 2018. Effects of a biostimulant derived from the brown seaweed Ascophyllum nodosum on ripening dynamics and fruit quality of grapevines. Scientia Horticulturae, 232, 97-106.

Gutiérrez-Gordillo, S., García-Tejero, I.F., García-Escalera, A., Galindo, P., Arco, M.C., Durán Zuazo, V.H., 2019. Approach to Yield Response of Young Almond Trees to Deficit Irrigation and Biostimulant Applications. Horticulturae, 5, 38.

Povero, G., Mejia, J.F., Di Tommaso, D., Piaggesi, A. and Warrior, P., 2016. A systematic approach to discover and characterize natural plant biostimulants. Frontiers in plant science, 7, 435.

Saa, S., Olivos-Del Rio, A., Castro, S., Brown, P.H. 2015. Foliar application of microbial and plant based biostimulants increases growth and potassium uptake in almond (Prunus dulcis [Mill.] D. A. Webb). Frontiers in Plant Science. 6, 87.

Soppelsa, S., Kelderer, M., Casera, C., Bassi, M., Robatscher, P. and Andreotti, C., 2018. Use of biostimulants for organic apple production: effects on tree growth, yield, and fruit quality at harvest and during storage. Frontiers in plant science, 9, 1342.

Tanou, G., Ziogas, V. and Molassiotis, A., 2017. Foliar nutrition, biostimulants and prime-like dynamics in fruit tree physiology: new insights on an old topic. Frontiers in Plant Science, 8, 75.

Building Disease-Suppressive Soils for Organic Agriculture


Effective organic farming begins below ground in just a few inches of high-quality topsoil. Intuitively, we recognize healthy soil in the spongy give beneath our feet. We can scoop it up, see the dark color and smell the distinctive, rich aroma of organic matter and active microbiology. Bacteria, fungi, archaea, nematodes and nameless other organisms quietly feed and defend our crops against pests and pathogens.

Crop protection challenges every grower, but in organic production, controlling pests and pathogens proves especially difficult. Without synthetic pesticides, root and foliar diseases often take a greater toll, and insect pressure can become overwhelming. While organic crop protection materials provide indispensable support, integrating preventative measures may greatly improve crop quality and yield.

Countless microscopic soil organisms orchestrate dynamic defense strategies against a small fraction of pathogens. By feeding, coaxing and fostering the soil’s beneficial life, organic farmers can turn on ancient defense mechanisms to suppress soil borne diseases and herbaceous insects. Healthy rhizosphere ecosystems evolved over millennia to cope with biotic and abiotic stress. Organic growers can improve crop protection by stewarding healthy soil microbiology. In return, the microbes will diminish disease symptoms by increasing nutrient availability, improving soil quality and inducing plant systemic resistance against pests and pathogens.


Nutrition as Pest Defense

Crop nutrition directly impacts crop protection. Plants rely on essential macro and micronutrients throughout their life cycle not only to support growth, but also to defend against invading pests and pathogens. In conventional farming, growers can apply precise quantities of macro and micronutrients in plant available form. Organic growers must rely on soil microorganisms to break down complex organic matter into simple, plant available nutrients.

Nitrogen, phosphorus, potassium and micronutrient availability depends on how quickly and effectively the soil microbes can metabolize and release nutrients. Microbial activity depends on soil moisture, temperature, carbon to nitrogen ratio and many other factors. Growers can create a soil environment conducive to microbial nutrient cycling by feeding microbes plenty of carbon, keeping the carbon to nitrogen ratio around 20:1 and keeping the soil moist but not saturated. Organic growers feed the microbes and the microbes feed the crops. Supplying frequent, moderate doses of liquid organic fertilizer can also stabilize nutrient availability, preventing spikes and crashes caused by high rates of manure or pre-plant fertilizer.

Nitrogen is the most limiting nutrient to crop growth and, without an adequate supply, development slows, and plants often suffer increased damage from disease and pests. Providing enough N to meet demand at critical growth stages will help seedlings mature quickly and develop strong root systems resilient against disease. Too much nitrogen can be equally damaging. Excessive N increases vegetative growth, and pests and pathogens are drawn to the crop to feed on succulent, tender young tissue2. Frequent leaf and soil tests can help determine N availability and fertilizer requirement.

Phosphorus availability also affects disease suppression. P is critical to root development, so supplying adequate available P will help plants develop mature root systems as quickly as possible to evade infection during their vulnerable infancy2. P availability greatly depends on pH, so adjusting the soil pH to around 6.5 with sulfur, lime or lots of organic matter can help support healthy root development. Adding too much P can harm crop growth and disease suppression, limiting the growth of some beneficial fungi that can outcompete or inhibit pathogens. Beneficial fungi also aid nutrient and water uptake, indirectly proving disease management by facilitating vigorous growth. Excessive P also decreases zinc availability, potentially causing deficiency symptoms that increase pest and pathogen damage.

Potassium, calcium and micronutrients play critical roles in cell wall stability and plant defense. Deficiencies lead to cracks and damage in cell walls and membranes, giving pathogens entry points into the plant. Fertilizing with adequate K, Ca and micronutrients builds thick, protective cell walls rich in lignin and suberin that resist breakdown by enzymes released by attacking pathogens. Nutrient deficiencies also cause sugars and amino acids to build up in cells because the plant does not have the nutrients needed to transform simple building blocks into complex carbohydrates and proteins. Sugars and amino acids leak out of weak cell walls, attracting and feeding pests and pathogens.

Soil Quality

Microbial activity and organic matter influence disease suppression by improving many aspects of soil quality including structure, pH, cation exchange capacity and water holding capacity. Good soil structure with stable aggregates and plenty of pore space favor healthy root growth and beneficial microbial colonization. Fusarium wilt often occurs in acidic, saturated soils when pathogenic fungi prey on oxygen-starved roots. Without adequate porosity, crops either get too much or too little moisture, making them weak, inhospitable to beneficial microorganisms and susceptible to pathogenic attack. Maintaining structured, well-aerated soils gives roots the best opportunity to grow and develop strong beneficial microbial associations. The good fungi and bacteria will occupy space on the roots and adjacent soil, competitively inhibiting pathogens and parasites.

Soil microorganisms are ecosystem engineers that modify their surroundings to suit their needs. Fungi and bacteria excrete sticky substances that bind soil particles together, creating aggregates and pore spaces that facilitate water, nutrient and air flow. By cover cropping and applying compost and carbon-rich organic fertilizers, growers provide a food source to fuel microbial growth and soil structure development. Over time, fungal and bacterial colonies will change the soil’s physical and chemical characteristics, creating an environment suppressive to pathogens.

Organic matter also contributes to disease management by increasing water holding capacity and cation exchange capacity. Organic matter has a very high water holding capacity compared to the mineral fraction of soil. Organic matter soaks up water like a sponge, slowly releasing moisture without suffocating plant roots. Organic matter also has very high cation exchange capacity, meaning it can attract and hold positively charged plant nutrients such as ammonium, potassium and calcium. Improved nutrient and water holding capacity provide plants with plenty of nutrients needed for vigorous growth and defense against stress.

Induced Resistance

Increasing soil microbial activity also helps fight biotic stress by activating the plants’ “induced resistance” against attacking organisms. Researchers describe two main types of induced resistance – Systemic Acquired Resistance (SAR) and Induced Systemic Resistance (ISR). Both forms activate plant defense genes and enhance protective mechanisms. SAR increases salicylic acid levels and is associated with accumulation of pathogenesis-related (PR) proteins.

Many different microorganisms and some abiotic chemical compounds can activate SAR. ISR relies on activation by plant-growth promoting rhizobacteria (PGPR) such as some types of Pseudomonas living symbiotically in the root system5. ISR also differs from SAR in defense mechanism. ISR is associated with the plant hormones jasmonic acid and ethylene and does not cause an accumulation of PR proteins. Both types of resistance prime the plant to recognize and strongly respond to a wide range of pathogens by launching chemical and physical defenses against infection.

Build Suppressive Soils

Pest or pathogen presence alone does not inevitably result in disease. The interaction between pathogen, host and the surrounding environment determines the outcome. Effective organic crop protection requires altering the soil environment and caring for the crop in ways that favor beneficials and suppress pathogens. Growers can promote healthy soil ecosystems by adding carbon with cover crops, compost and organic fertilizers. Following nutrient management plans based on soil and leaf tests will provide the nutrition needed to support vigorous growth and systemic resistance to biotic stress. Finely tuned nutrient management and pathogen suppressive soils will bolster crop growth and maximize the plants’ innate ability to ward off pests and disease.

Eryn Wingate is an agronomist with Tri-Tech Ag Products Inc. in Ventura County, Calif. Eryn creates nutrient management plans for fruit and vegetable growers to improve yield and crop quality while promoting soil health and environmental protection.


1. Chandrashekara, C. & Kumar, Ravinder & Bhatt, J.C. & Kn, Chandrashekara. (2012). Suppressive Soils in Plant Disease Management. 10.13140/2.1.5173.7608.

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Getting Started with a Hemp Operation


Growing hemp was outlawed in 1970, but since the California Hemp Farming Act was signed into law and became effective on January 1, 2017, hemp is again a legal crop. Still, not just anyone can throw their hat in the ring to legally grow hemp. There is a somewhat involved registration process to wade through first, as well as rules and regulations for California hemp growers to follow. Here’s a brief overview.


Getting Registered

Farmers wishing to grow hemp must pay a $900 fee and apply for registration with the agricultural commissioner in the county where they plan to grow the crop. A separate registration is required for each county in which a grower wishes to produce hemp. Besides detailed contact information, the application must also include the legal description of land that will be used for growing or storing hemp along with the GPS coordinates and a map. Growers must list the hemp cultivars they intend to plant along with the state or country of the cultivar’s origin. They must also describe a plan for testing their plants as well as a proposal to destroy any plants with a THC level above 0.3%. Hopeful hemp growers must also submit a criminal history report.

If a grower’s application is approved, they become a registered grower. The registration is valid for one year. It must be renewed annually at least 30 days before the prior year’s registration expires, and include a $900 renewal fee. Registration and renewal fees may vary from county to county. The ag county commissioners will keep hemp records for at least three years.

If a registered grower wants to change the land area for growing or storing hemp, he must submit an updated registration. The same holds true if he wishes to switch cultivars.

Only approved certified hemp cultivars are allowed. The approved cultivar list may be updated with varieties added, amended or deleted. At least one public hearing will be held before making a change to the list. Only registered agricultural research institutes or registered hemp breeders may legally develop new cultivars.

Industrial hemp has thousands of uses.


Plant Testing

Sampling hemp plants to test for acceptable THC levels must be done no more than 30 days before harvest. The grower or breeder must be present when samples are collected. Sampling is done by the county ag commissioner or a sample-taker assigned by the commissioner.

Each primary sample will include all parts of the plant—stems, stalks, flowers, buds and seeds, if applicable. Five or more primary samples make up one composite sample which will be taken from each field or from each cultivar within the same field. Indoor and outdoor growing areas are treated as separate fields. Check with the California Department of Food and Agriculture (CDFA) for exact testing procedure, including the number of plants to be tested per field and the portion of the plant that is tested.

Samples, along with the grower’s proof of registration and other documents, are sent to a laboratory approved by the CDFA. The lab must use approved testing methods. The percentage of THC is measured on a dry-weight basis.

The samples will receive a pass or fail report— a pass if the test shows 0.3% THC or less. The grower will receive at least 10 copies of a pass report. The lab keeps report records for two years or more. Growers are required to do the same and must make reports available to the CDFA, the commissioner or law enforcement if asked.
If the plant samples fail with levels over 0.3% but not over 1%, the grower will submit additional samples. If the crop sampling fails a second time, the plants must be destroyed.

The amount of time given for growers to destroy the crop depends on the THC level. If levels fall between 0.3 and 1% THC, plant destruction needs to happen as soon as possible, with growers given a time frame of no more than 45 days after receiving a failed lab report. If plant samples fail with a THC level over 1%, destruction of the crop must begin within 48 hours and be completed within a week.

Exceptions for higher THC levels may be authorized for a registered and established research institute for approved hemp cultivar breeding purposes.

California hemp growers, new and old, must follow a slew of regulations to operate within the hemp industry. (photo by D. Cahill.)


Violations and Consequences

A first-time offender is given a chance to redeem their mistake. If a hemp grower, breeder or researcher commits a negligent violation that is not considered a repeat offense, a corrective plan is put into place by the CDFA secretary. The plan will include a reasonable date to correct the violation.

Once a grower, breeder or researcher is negligent, he is put on a sort of probationary status. For at least the next two years, he must periodically report to the secretary and verify his compliance.
Three strikes and you’re out: If a hemp grower, breeder or researcher commits a negligent violation three times within a five-year span, he is ineligible to take part in the hemp-growing program for five years after the date of his third violation.

Violations deemed intentional, reckless or grossly negligent will be immediately reported by the secretary to the U.S. Attorney General and the California Attorney General.

Anyone who has been convicted of a felony on or after Jan. 1, 2020, which involves a controlled substance under either state or federal law, cannot take part in the California Industrial Hemp Program for 10 years after the date of conviction.

Thou shalt not lie: Anyone who falsifies information on the application or registration is not allowed to take part in the California industrial hemp program.


Hemp Advisory Board

The Industrial Hemp Advisory Board is made up of 13 members, including five registered hemp growers, two agricultural researchers, one representative from the State Sheriffs’ Association, one county ag commissioner, one representative of the Hemp Industries Association, two representatives of businesses that sell industrial hemp products and one member of the public.

The board advises the CDFA on things such as annual budgets, industrial hemp seed law and regulations, enforcement and setting fees. Board members serve a three-year term. That term for current board members runs through May 31, 2023. The board meets at least once a year. Positions are not salaried, but board members may be compensated for travel expenses.


A Look at the Numbers

As of July 2, 2020, there were 553 registered industrial hemp growers and breeders in the state; 1,077 registered cultivation or research sites; and 26,226.3 registered acres.

Leading counties include Riverside with 101 growers and breeders, 152 sites and 8,191.5 acres; San Diego with 78 growers and breeders, 130 sites and 509 acres, and Fresno with 48 growers and breeders, 97 sites and 2,200 acres.

Other counties have fewer growers than those mentioned above, but more than 2,000 acres each in hemp production: Kern County with 2,287 registered acres, Ventura with 2,583 and San Bernardino with 2,763 acres.

Industrial hemp plant products including tea, oil, rope and protein powder on 100% hemp fabric.