ANR Green Blog
The strawberry industry ended a long good-bye to methyl bromide in 2016. The fumigant had been used for decades to kill a wide range of soil-borne pathogens, weed seeds and insects, permitting the California strawberry industry to flourish. Scientists determined it was an ozone-depleting chemical in 1991, but its phase-out was delayed for years because of lack of equally effective alternatives.
Strawberry farmers now use a combination of approaches, including fumigation with other chemicals, soil oxygen deprivation, biofumigants, and beneficial microbes that improve soil biology. A greater arsenal is needed.
“Growers have three or four chemical alternatives, some are used alone and others in various combinations,” said UC Cooperative Extension advisor Surendra Dara. “Now, certain minerals, beneficial microbes and biostimulants are becoming available to enhance plant's natural defenses and improve strawberry growth, yield and health in an era without methyl bromide.”
Dara conducts research and advises strawberry and vegetable growers in the Central Coast counties of San Luis Obispo and Santa Barbara. Each year he holds a field day that attracts nearly 200 farmers, pest control advisers and representatives of allied industries to Manzanita Berry Farms outside Santa Maria. The agenda for the May 9 event included preliminary results of trials studying a number of commercially available and soon-to-be available biological and synthetic amendments to improve strawberry plant health, berry quality and yield.
Dara was ill, so Manzanita Farm owner Dave Peck reviewed the handout prepared by Dara for the field day. Manzanita Farms is one of two sites where Dara is testing products in replicated plots. Other studies are conducted in strawberries grown at the Shafter Research Station, a privately managed agricultural research facility in Kern County.
Several products resulted in increased marketable yield of strawberries during the February 2018 to April 2018 study period. See the preliminary results here. Data collection will continue through the end of the strawberry season.
“A challenge was that many people did not have complete faith in biologicals a few years ago,” Dara said. “By conducting multiple studies year after year, we are able to generate critical data that is useful for the farmers as well as companies that produce biologicals. By using different application strategies and rates, and a combination of techniques - as appropriate for their situations - farmers can engage in sustainable strawberry production.”
When San Juan Bautista resident Michael Cent was looking for ways to rehabilitate a large backyard pasture infested with invasive foxtail weeds, he called Devii Rao, the UC Cooperative Extension range and natural resources advisor in San Benito County.
Though Rao works mainly with large, commercial producers, she was intrigued by Cent's well thought out plans to replace foxtail with more desirable plants using sustainable practices. She paid him a visit.
Behind the home sits a two-acre fenced pasture where previous owners grazed llamas and ran horses. The picturesque setting adjoins San Juan Creek and frames a panorama of farm fields and the Diablo Mountain Range. But the tableau was spoiled by fence-to-fence foxtails, an exotic plant that hails from the Mediterranean, offers poor forage value and presents nuisance characteristics.
“The seed heads get stuck in the eyes, ears and noses of livestock and pets,” Rao said. “Foxtail is an annual grass that is difficult to control, but that didn't stop Michael Cent from trying.”
Cent is a pharmacist and self-described plant nerd.
“He turned his foxtail problem into a science project,” Rao said.
As a pharmacist, Cent said he is technically a chemist. “When you look at botany as chemistry, if you drill down into all the chemical reactions going on, it's amazing.”
Cent tested the soil Ph and nutrients. He identified 12 plants that would thrive under his pasture conditions and potentially out-compete the foxtails.
“In my research, much of what I see is not native,” Cent said. “My expectations to plant only natives have tempered. It's good to do within reason, but if a benefit of a non-native species outweighs a lesser advantage of being native, I'll go with the non-native species.”
Cent borrowed a tractor to break up the soil and reseeded by hand with his chosen grass and broad leaf plants. He kept detailed notes.
- Birdsfoot trefoil grew a dense carpet that choked out everything.
- Crimson clover germinated and grew quickly early in the season, but didn't do as well as anticipated.
- Harding grass was seeded specifically to out-compete the bristly ox-tongue, another undesirable plant.
- Chicory has a deep taproot, which helps it survive the dry season.
- Oxalis has come in like gangbusters, even though it wasn't seeded.
At first Cent regularly mowed the pasture to keep down the foxtails, but when the job became forbidding, he contracted with a company to bring in goats to aid control.
After four years of effort to overcome foxtail with grazing goats and seeding plants, Cent has come to a realization.
“I thought I could set it in motion and it would take care of itself,” Cent said. “But it's going to take a sustained effort.”
What drives Cent's devotion to rehabilitating a pasture with extensive plant research and management? The miracle of life, he said.
“The marvel of putting a seed in the ground, managing it and seeing what becomes of it. It's fascinating,” Cent said.
As sorghum plants cope with drought conditions, the plants' roots and adjoining microbial communities are communicating in a chemical language that appears to improve the plants' chances under water stress.
“It's amazing,” said Peggy Lemaux, UC Cooperative Extension specialist. “We know there are lots of microbes in the soil and, for the most part, ones in the surrounding soil stayed the same under drought conditions. We only saw changes in those microbes closely associated with the roots.”
The role of drought in restructuring the root microbiome was the first published discovery to come out of a sweeping drought research project underway since 2015 in the fields at UC Kearney Research and Extension Center in Parlier. The five-year study, funded with a $12.3 million grant from the Department of Energy, aims to tease out the genetics of drought tolerance in sorghum and its associated microbes. Using sorghum as a model, scientists hope the research will help them understand and improve drought tolerance in other crops as well.
The new research results from the lab of USDA's Devin Coleman-Derr at UC Berkeley, published April 16, 2018, in the Proceedings of the National Academy of Sciences, document the fate of microbes associated with sorghum roots under three distinct irrigation regimens. Because the San Joaquin Valley generally sees no rain during the growing season, it is the ideal place to mimic drought conditions by withholding irrigation water.
All plots received a pre-plant irrigation to initiate growth. In the control plots, sorghum was irrigated normally, with weekly watering through the season. In the plot simulating pre-flowering drought stress, the plants received no additional water until flowering, about halfway through the season. The third treatment was watered normally until it flowered, and then water was cut off for the rest of the season.
Beginning when the plants emerged, the scientists collected samples from each plot on the same day and time each week for 17 weeks. In a mini, in-field laboratory, roots, rhizosphere (zone surrounding the root), leaves and soil samples from 10 plants in each plot were immediately frozen and transported to Berkeley, where they were disseminated to collaborators, who investigated the plant and microbial responses at the molecular level.
“When a sorghum plant is subjected to drought, it starts sloughing off metabolites, nutrients and amino acids from the roots. The compounds appear to communicate to the neighboring microbial community that the plant is under stress,” Lemaux said. “That selects out a certain population of microbes. Certain types of microbes increase, others go away. When you add water back, the microbial community returns to its pre-drought population in just a few days.”
The researchers cultured two specific microbes that were enriched in the rootzone under drought conditions. They coated sorghum seeds with the microbes and planted them under drought conditions in a growth chamber. This treatment encouraged the plant to grow more roots.
“The microbes appear to improve plant growth during drought,” Lemaux said. “Those microbes appear to be helping plants survive drought. We didn't know that was happening before we got these results.”
Lemaux said the research might lead to future field use of the research breakthrough.
“A lot of companies are interested in the microbiome,” she said. “Some are already selling microbes to coat seeds.”
Pests have always been a bane of human existence. Modern society has developed effective pest management, “but there is no kind and gentle way to kill things,” said Brian Leahy, the director of the California Department of Pesticide Regulation, in remarks at the April 2018 IPM Summit.
The ever increasing incidence of invasive pests and the concerns about how to manage them will be a continuing challenge. Leahy said society is on a pest treadmill; and the best way to address it is with integrated pest management (IPM).
The concept of integrated pest management emerged 60 years ago when scientists recognized that imposing a harsh chemical on a natural system threw it off kilter, often causing unexpected, usually negative consequences. They realized that combining an array of pest control methods – such as careful supervision of insect levels, promotion of beneficial insects, and using less harsh products – would be more effective, safer for families and farmworkers, and kinder to the environment in the long run.
And yet, pesticides are still widely used in agricultural, horticultural and structural systems.
“We need to make IPM more robust,” said Pete Goodell, UC IPM advisor emeritus who spent 36 years as an IPM researcher, leader and teacher. “We need to make IPM easier to adopt.”
The meeting in Davis brought together nearly 200 people engaged in the science, business and regulation of pest management. They were assembled to address the tensions around pesticides and their alternatives, and usher in a new generation of researchers and practitioners to maintain and expand on six decades of progress in integrated pest management.
The IPM Summit is the final chapter of a collaborative effort titled “The Pests, Pesticides & IPM Project,” which was funded by DPR to enhance dialog about pest management. The project leader is Lori Berger, UC IPM academic coordinator.
“This project addresses the challenges pests pose to society,” Berger said. “We want to increase adoption of IPM practices on farms, and also in schools, homes, museums and golf courses. We're all in this together.”
One example of urban IPM efforts was presented by the IPM Summit keynote speaker Kelly Middleton, director of community affairs for the Greater Los Angeles County Vector Control District. She outlined the substantial public health concerns associated with pest control in California's largest urban area. A primary target is mosquitos.
“In the early 1900s, vector control started with concerns about malaria and mosquito populations,” Middleton said.
Over decades, the vector control district worked behind the scenes to keep mosquito populations in check. But in recent years, new species of mosquitos capable of spreading Zika, West Nile encephalitis, chikungunya and yellow fever have made their way to LA, intensifying concerns.
A key IPM tool in Los Angeles is minimizing standing water where mosquitos can breed. With year-round water flow irrigating vast landscapes and concrete drainages that inhibit infiltration, the vector district is faced with mosquito breeding grounds created by “urban drool,” Middleton said.
Trash rife with nutrients – such as discarded food and plant materials – are perfect nourishment for immature mosquitos, a condition referred to as “urban gruel.”
Higher temperatures predicted because of climate change only threaten to exacerbate the problem.
“A warming world is a sicker world,” Middleton said.
An effective IPM approach to mosquitos is short-circuiting their reproduction opportunities by enlisting residents to maintain swimming pools, drain any receptacles that can capture rainwater or irrigation, and be vigilant about basins containing water in their environments.
These efforts are emblematic of the societal collaboration that can tackle pest problems without pesticides.
In his IPM Summit presentation, Goodell called for public sector investment in basic research, applied research, extension and education to find IPM solutions and encourage implementation. He appealed for IPM outreach to include community organizations, home owners associations and other non-traditional partners. He suggested agriculture take advantage of farmworkers' presence in the field for early pest detection.
“Technical pest management skills are critical, but it's connections with people that are key to bringing about change,” Goodell said.
Help the environment on Earth Day, which falls on Sunday, April 22, this year, by growing insectary plants. These plants attract natural enemies such as lady beetles, lacewings, and parasitic wasps. Natural enemies provide biological pest control and can reduce the need for insecticides. Visit the new UC IPM Insectary Plants webpage to learn how to use these plants to your advantage.
The buzz about insectary plants
Biological control, or the use of natural enemies to reduce pests, is an important component of integrated pest management. Fields and orchards may miss out on this control if they do not offer sufficient habitat for natural enemies to thrive. Insectary plants (or insectaries) can change that — they feed and shelter these important insects and make the environment more favorable to them. For instance, sweet alyssum planted near lettuce fields encourages syrphid flies to lay their eggs on crops. More syrphid eggs means more syrphid larvae eating aphids, and perhaps a reduced need for insecticides. Similarly, planting cover crops like buckwheat within vineyards can attract predatory insects, spiders, and parasitic wasps, ultimately keeping leafhoppers and thrips under control.
Flowering insectaries also provide food for bees and other pollinators. There are both greater numbers and more kinds of native bees in fields with an insectary consisting of a row of native shrubs planted along the field edge (called a hedgerow). Native bees also stay in fields with these shrubs longer than they do in fields without them. Therefore, not only do insectaries attract natural enemies, but they can also boost crop pollination and help keep bees healthy.
Insectary plants may attract more pests to your plants, but the benefit is greater than the risk
The possibility of creating more pest problems has been a concern when it comes to installing insectaries. Current research shows that mature hedgerows, in particular, bring more benefits than risks. Hedgerows attract far more natural enemies than insect pests. And despite the fact that birds, rabbits, and mice find refuge in hedgerows, the presence of hedgerows neither increases animal pest problems in the field, nor crop contamination by animal-vectored pathogens. Hedgerow insectaries both benefit wildlife and help to control pests.
How can I install insectary plants?
Visit the Insectary Plants webpage to learn how to establish and manage insectary plants, and determine which types of insectaries may suit your needs and situation. If you need financial assistance to establish insectaries on your farm, consider applying for Conservation Action Plan funds from the Environmental Quality Incentives Program (EQIP) offered by the Natural Resources Conservation Service.
- Flower flies (Syrphidae) and other biological control agents for aphids in vegetable crops. (PDF)
- Good news for hedgerows: no effects on food safety in the field.
- Hedgerow benefits align with food production and sustainability goals.
- Habitat restoration promotes pollinator persistence and colonization in intensively managed agriculture. (PDF)
- Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops.