Posts Tagged: integrated pest management
Strawberries, which generated $2.2 billion for California growers mainly on the coast in 2019, are sensitive to soilborne diseases. Strawberry plant roots infected by fungi are unable to take in nutrients and water, causing the leaves and stems to wilt. The diseases reduce fruit yields and eventually kill infected plants.
To protect the delicate plants from pathogens, strawberry growers fumigate the soil with pesticides such as chloropicrin and 1,3-dichloropropene before planting transplants. Due to the potential negative effects on the environment and human health, however, use of fumigants are highly regulated and developing non-fumigant alternatives has been a priority of the strawberry industry.
For a biological alternative to manage soilborne diseases in strawberries, Joji Muramoto, UC Cooperative Extension organic production specialist based at UC Santa Cruz, has received a $411,395 grant from USDA National Institute of Food and Agriculture to study the ability of other crops to suppress strawberry pathogens in the soil.
Verticillium wilt, caused by Verticillium dahliae, is a common soilborne disease that can be controlled with anaerobic soil disinfestation (ASD), a fermentation-based biological treatment using carbon sources such as rice bran under plastic mulch in moist soils for 3 to 5 weeks in autumn. About 2,000 acres of berry fields, mostly organic, were treated with ASD in California and Baja California, Mexico, in 2019.
In 2008-09, the diseases fusarium wilt, caused by Fusarium oxysporum f. sp. fragariae, and charcoal rot, caused by Macrophomina phaseolina, emerged in Southern California and now threaten strawberry plants throughout the state.
ASD isn't as effective against F. oxysporum and M. phaseolina unless it is applied in summer on the coast. As saprophytes, they feed not only on living plants, but also can colonize crop residues and rice bran especially at lower coastal temperatures in autumn. Treating fields on California's coast with ASD during summer is difficult because it competes with the vegetable production period.
Based on promising studies in Asia and other areas, Muramoto plans to test alliums – such as onion, bunch onion and leek – and a certain variety of wheat (Summit 515) to see if they will suppress F. oxysporum and M. phaseolina. His team will conduct a series of greenhouse and field trials and test these crops with and without ASD to compare the effects on soilborne pathogens.
“Studies have shown the potential of using allium crops to control Fusarium wilt, and Summit 515 wheat for charcoal rot,” Muramoto said. “Our goal is to examine the effectiveness of suppressive crops, optimize them for California strawberry production systems, and evaluate their economic feasibility for commercial use.”
“No single tactic is likely to replace fumigants,” he said. “Integration of multiple biological approaches such as crop rotation, ASD, and use of resistant strawberry varieties is a key to develop a successful non-fumigant-based soilborne disease management strategy for strawberries. This project is a part of such broader efforts.”
At the end of the three-year study, he plans to share the results at workshops, field days and webinars.
Rachael Goodhue, UC Davis professor of agricultural economics; Carol Shennan, UC Santa Cruz professor of environmental studies; and Peter Henry, USDA Agricultural Research Service plant pathologist, are co-principal investigators on the study with Muramoto.
Also collaborating on the project are Christopher Greer, UC Cooperative Extension integrated pest management area advisor in San Luis Obispo County; Oleg Daugovish, UCCE vegetable and strawberry advisor in Ventura County; Mark Bolda, UCCE director strawberry and cane berry advisor in Santa Cruz County; Jan Perez, food systems specialist, and Darryl Wong, farm research manager, at UC Santa Cruz Center for Agroecology and Sustainable Food Systems; Miguel Ramos of Ramos Farm; Agriculture and Land-Based Association (ALBA); Driscoll's; Naturipe; and The Oppenheimer Group.
Spotting ants in the home or yard is no reason to reach for insecticide sprays or call an exterminator. UC Cooperative Extension experts say the insects can be managed by residents in ways that are effective, inexpensive, safe and environmentally kind.
“Ants are probably the No. 1 most common pests of our homes and gardens,” said Carolyn Kinnon, an environmental horticulturist and instructional associate at Mira Costa Community College. “Scientists find chemicals in our waterways that include pesticides commonly used to kill ants.”
Kinnon teamed up with UCCE community education specialist Scott Parker to present a Healthy Garden-Healthy Home online ant workshop during the COVID-19 pandemic to take the place of a planned in-person event. Healthy Garden-Healthy Home was initiated in 2005 with a grant from the California State Water Resources Control Board and continues with funding from San Diego County. With the move online, the workshop attracted four times more participants that usual.
“A silver lining of the COVID disaster has been our ability to reach out to many more individuals,” Parker said.
Healthy Gardens-Healthy Homes aims to cut residents' use of chemicals and reduce soil erosion that can wash into gutters with irrigation or rain water, course through storm drains and into streams, reservoirs and the Pacific Ocean. During the recent UCCE webinar on healthy ant control, Kinnon introduced science-based solutions that can be combined to keep ants at bay.
Use ant biology to battle ants
Ants are always looking for food and will forage any accessible source. Short circuiting this biological need is the first approach to controlling the pest. Outside, ants are often attracted to a sticky, sweet honeydew that pests like aphids leave behind when they feed on plants. Washing off aphids and honeydew with a sharp stream of water from the hose reduces the food source.
In spring, Kinnon said, ants like to feed on proteins, like seeds, nuts, dog food and other fatty substances. Fallen nuts, bird seed and leftover pet food should be discarded to reduce ant activity.
“When honeydew production from sap-sucking insects declines in the hot summer, and there is an absence of food sources outdoors, ants may come indoors,” she said. “Ants will travel several hundred feet in search for food.”
Removing inside food sources – like spills on counters and floors – and blocking access – by filling in holes and cracks – is the first defense against an indoor ant invasion. Kinnon recommends keeping food containers clean and sealed, rinsing empty recyclables – particularly sugar-sweetened beverages – and wiping up grease on barbecues and stove tops.
Wipe up ants and their chemical trails with an all-purpose cleaner, and fill tiny gaps, cracks and holes with caulk to make their entry difficult.
Another way to achieve environmentally friendly ant management is coming to terms with the fact that they can't be eliminated from outdoor areas.
“Our goal is to focus on reducing population numbers,” Kinnon said. “We have to tolerate a certain number.”
Spraying a pesticide on an ant trail or sprinkling granular pesticides will only kill a fraction of the ants in the yard. Those materials can run off and pollute watersheds.
If cleaning up food sources, exclusionary measures and increased tolerance aren't enough, pesticide baits are an additional integrated pest management tool.
“This works because female worker ants take the bait back to the nest and feed it to other ants in the colony,” Kinnon said.
The bait must be slow acting so it doesn't kill the worker before she gets back to the colony. Kinnon recommended baits with no more than .5% active ingredient. For best bait placement, follow trails to find the nest and place the bait close by in a safe bait station. If the nest can't be found, the bait station can be placed along the trail.
To control spider mites, many almond farmers have taken to routinely spraying their trees with a miticide in May. However, research by UC Integrated Pest Management advisor Kris Tollerup shows that the pesticide application could cause more harm than good.
“The preventative sprays do suppress spider mite populations, but there's no beneficial effect because the mites show up very late in the season and the population density remains well below an economic level,” Tollerup said. “A natural enemy, six-spotted thrips, will likely show up and suppress the mite population before any damage occurs.”
Tollerup recommends almond farmers monitor their orchards for spider mites and six-spotted thrips to determine whether treatment is necessary.
During the 2017 growing season, about 517,000 acres of almonds in California received a preventative miticide application in May; 93% were treated with the insecticide abamectin.
“This strategy runs counter to sustainable integrated pest management practices,” Tollerup said. “The sprays adversely impact spider mite natural enemies and are based on the calendar, not on the monitoring and economic thresholds that the UC Statewide IPM program has determined help reduce pesticide applications.”
The heavy reliance on abamectin has also caused some spider mites in the mid-San Joaquin Valley to become 16 times more resistant to the miticide than susceptible populations.
Tollerup worked with the Almond Board of California and a large grower in Kern County to compare the effectiveness of the preventative miticide spray with plots that were simply monitored for pests and natural enemies.
“Tollerup and other UCCE advisors have correctly identified the problem and spoken out both in public and private about not treating unless economic thresholds have been met,” said a pest control adviser working in Kern County. “Because of Tollerup's role, we have been able to collaborate with farmers to hold off on spring treatments at many ranches and only treat when warranted, which has essentially removed a spray treatment on a vast number of acres.”
Surveys conducted after the trial results were released showed that 80,000 acres of almonds were not treated with miticide sprays in May 2018 and May 2019. The change in strategy resulted in a savings to farmers of about $2.2 million in miticide and application costs.
Moreover, Tollerup calculated a subsequent reduction of 880,000 pounds of carbon dioxide emissions due to reduced use of diesel tractors and motor-driven application equipment associated with the miticide spray.
For more information on integrated pest management of spider mites, see the UC Integrated Pest Management website and IPM of spider mites on almond improves farm profitability and air quality.
Help the environment on Earth Day, which falls on April 22, 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.
Recent surveys in the North Coast have found that 90 percent of the powdery mildew samples collected were resistant to strobulurin fungicides, the director of UC Integrated Pest Management Program told legislators at a joint hearing of the California Assembly and Senate Select Committees on California's Wine Industry. A potential solution is breeding winegrapes to be resistant to powdery mildew, but a drawback is that the wine industry is largely known for its varietals.
“Professor Andy Walker at UC Davis has succeeded in crossing winegrapes with a wild grape species that is naturally resistant to powdery mildew and then crossing the offspring back to the parent winegrape variety for several generations,” said James Farrar, who was invited to speak at the committees' informational hearing on “Fire Recovery and Pest Management Awareness” at UC Santa Barbara on Nov. 7.
Farrar warned the legislators of increased human health risks due to “unintended consequences of social pressure” on the herbicide glyphosate, which growers use to control weeds under grapevines rather than tilling the soil, to comply with Natural Resources Conservation Service and Salmon Safe guidelines.
“Recent social pressure resulting from the International Agency for Research on Cancer labeling glyphosate a probable human carcinogen and news stories indicating detection of glyphosate in wine have caused some growers to look at other herbicides,” Farrar said. “The other choices are glufosinate, which is more risky to applicators, less effective, and more expensive, and paraquat, which has similar price and effectiveness, but much greater risk to applicators. Paraquat is a restricted-use pesticide that is highly toxic to humans – 3 teaspoons will kill an adult. It has a higher risk ‘Danger' label in contrast to the lower risk ‘Caution' label for glyphosate.
“This is an increased risk to human health as a result of misplaced public perception of risk.”
Farrar closed his comments by saying, “The County Agricultural Commissioners and county-based University of California Cooperative Extension advisors are vital in the continued efforts to manage winegrape pests and diseases. They are the frontline support for growers and pest control advisers in this effort.”