Why insectary habitats are key in organic agriculture

By Thomas Grandperrin of UAV-IQ Precision Agriculture

In agriculture, input distribution companies are essential stakeholders for their role as intermediaries between manufacturers of new products and growers. Their research programs and continuous education to growers are also important, to make sure the products are used properly as part of tested protocols.

To get the perspective of an agricultural products distributor on organic farming, I reached out to Gina Bella Colfer, who is the key account manager for organic agriculture for the well-known fertilizer, plant protection, and other agricultural inputs company Wilbur Ellis. 

Gina has been a pest control advisor (PCA) for 30 years and a certified crop advisor (CCA) for over 15 years with a sub-specialty in sustainability. She works with some of the main crops of the Salina Valley, California such as leafy greens, broccoli, cauliflower, and artichoke. 

Gina has extensive knowledge of organic vegetable crop production systems, and one of her primary roles is to help Wilbur Ellis’ salespeople who work in organics to better understand the most effective methodologies and products. During her career, she has also helped develop organic fertility products tailored for soil health.

During our conversation, we touched upon various topics such as conservation biological control, the use of beneficial insects in vegetable crops, and the promotion of soil health. These practices are not only relevant for organic growers, but also for conventional farmers wishing to improve their crop health and long term profitability.

Creating insectary habitats to attract and sustain natural enemies populations

Biodiversity on the farm encourages the development of populations of naturally occurring beneficial insects that come to feed on the nectar and pollen of the plants that are flowering within or next to the planted fields.

“A lot of the adult predators rely on pollen and nectar as their sole food source but then it's their immature stages that are predaceous on the insect pest. The same thing is true for parasitic wasps, which are floral feeders at an adult stage, but it's their eggs that they lay within the pest that kills it. That is why, as a company, we really encourage permanent cover cropping in tree orchards and vineyards and strip habitat in row crops,” comments Gina.

When biodiversity is destroyed, the ecosystem gets out of balance. One of Gina’s goals is to actually promote that balance, as she believes that “it's just so important in the agricultural sector that we work with nature and not try to fight against it.”

She explains that adding insectary habitats in the field helps to reduce insect pests, but she warns growers that “it’s important to pick the right insectary habitat for your crop. You don’t want to pick insectary plants that will flower after the crop is done.

"We have seen some growers planting dill and cilantro that don’t bolt until after the lettuce is harvested, which is very ineffective. In comparison, if they direct-seed or transplant sweet Alyssum with the lettuce, it will flower way before the crop is close to being mature.

"In a long season crop though, like celery or a brussel sprout crop, a combination of alyssum, dill, and cilantro could work great to bring the floral diversity that will attract natural enemies.” 

The promising opportunities for biocontrol in outdoor vegetable row crops

In vegetable row crops like lettuces, some growers are having major issues with thrips that can transmit a virus called impatiens necrotic spot virus (INSV). The release of beneficial insects can be a cost-efficient pest management technique.

“The ideal scenario would be to have insectary habitats in place, like sweet alyssum planted as a strip crop or just within the crop, one bed every 30 or 40 beds, and release the predatory bug Orius insidiosus in it and let them feed out from there.”

Some growers also release green lacewing larvae, and a University of California Cooperative Extension entomologist is currently conducting a study in Monterey county to measure the effectiveness of this beneficial insect to control thrips and aphids populations.

Gina is confident that flowering strips are the most important part of successful pest control in organic vegetables.

“Where growers have created insectary habitat within a crop, they usually observe very little thrips and Lygus damage, thanks to naturally occurring enemies attracted by the food source and the refuge and keeping the pest populations down.”

But she admits that this is based more on anecdotal rather than empirical evidence. “Even if we’ve seen it working, we definitely need more formal research on that side we could fall back on and cite to prove that it actually does work.” 

Working with the soil and feeding it to prevent pests

A recurring concern among conventional growers who are considering transitioning to organic agriculture is that they fear they would have no tools to fight pests. While the release of natural enemies and the use of biocontrol products have already proven their effectiveness against many pests, the larger concern is that asking this question is more an indication of the wrong mindset than of a lack of information.

This question focuses on treatment, when the emphasis should be on prevention. As Gina explains, “I think a lot of conventional growers don’t realize that we see fewer insect pressures in organic than on conventional crops.”

The reduction of pest pressure doesn’t happen overnight and takes a lot of agronomic skills. It can take several years to realize the benefits of implementing organic farming practices. For more reasons than just the three-year process to get the organic certification, growers have to be consistent and stick with the program to improve the resilience of their farm. 

Gina explains that feeding the soil and giving the soil what it needs to grow healthy plants is critical. Without it, the implementation of insectary habitats and biocontrol would have limited effectiveness because insect pests are more attracted to unhealthy plants and plants with unbalanced nutritional content.

“It is really about building the soil and making it healthy through cover cropping and the use of soil input that help build the microbial communities, not only adding some NPK fertilizers to it and hoping to have a great crop. It helps grow plants that can have the ability to trigger its own resistance mechanisms and make it less desirable for pests.” 

As an example, Gina reminds growers that, “if the plant is too high in nitrogen, it is more attractive to insect pests because they're attracted to the nitrates in the plant. If you balance that, then you’ll have fewer pests attacking.”

But even if the needed nutrients are present in the soil, they might not be available to the plant. That’s when encouraging a healthy soil microbial is key according to Gina. “When you have an active microbial community in the soil around the root system, they're able to mineralize the nutrients within the rhizosphere, so that the plant can absorb them.”

The role of new technologies in organic agriculture

While implementing or revisiting traditional agroecology practices play an important part in organic agriculture, new technologies can also help implement more environmentally sustainable practices. Gina believes they can improve efficiencies and save money for organic growers.

In regions of the world where there are labor shortages such as California, it can be hard to hire a crew to perform weeding, thinning or other field tasks - and this situation got even worse during the Covid-19 pandemic.

Wilbur Ellis has started to offer a precision thinning service, using a tractor that can use organic contact herbicide (based on capric and caprylic acid) in vegetable row crop fields. In addition to the positive environmental impact of using less pesticides, this technology can have a significant economic advantage for growers.

Gina comments that in lettuce crops “it is a $400 per acre application versus a $1,000 to $3,000 per acre application, depending on your weed pressure”. In the Salinas Valley, some of Gina’s clients also hire drone service providers to apply biocontrol treatments on their vegetable crops to increase the effectiveness of their pest control program. 

Among all these Ag Tech solutions, it is probably the emerging technologies that map the microbiome genome of the soil in order to better understand its effects which aligns the closest with Gina’s focus on soil health. Gina is leading a Wilbur-Ellis collaboration with Trace Genomic, a company which was accelerated in the Salinas-based THRIVE Ag Tech Accelerator, to sample soil in the Salinas Valley with the goal of finding ways to increase the microbiome of the soil.

The role of organic and small family farms in the resiliency of society

To conclude our discussion, Gina describes her hopeful outlook of seeing organic farming develop and the preservation of the small family farms. She sees them playing an essential role in reducing food deserts, increasing the social impact agriculture has on communities experiencing economic downturn, and promoting environmental sustainability. 

“I think right now with all of this upheaval that we're experiencing with the Covid-19 and racial injustice, we are on the cusp of change, but in what direction do we take that change? I think farming, coming back to the land, learning more about our own health and what it takes to be healthy is part of the answer.

"We need to eat foods that are nutrient-dense to contribute to our health to help prevent diseases, just like plants need to eat from healthy soils to help prevent invasion from the myriad of pests that are waiting in the wings for the right conditions to attack.”

For both conventional and organic growers who are interested in staying up to date on the latest organic practices knowledge, Gina recommends following the Organic Trade Association (OTA), the Organic Farming Research Foundation as well as the California Certified Organic Farmers’s websites (CCOF). For Midwest growers interested in regenerative agriculture practices, she recommends the online magazine Acres USA as a great resource for educational content.

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  Yutian Lu

  yutian.lu@agropages.com