Posts Tagged: pest management
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.
Hedgerows bordering farmland – plantings with native trees, shrubs, bunch grasses and wildflowers – support bug-eating birds, which helps with on-farm pest control, according to research by recent UC Davis graduate Sacha Heath and UC Cooperative Extension advisor Rachael Long. The study was published in the October 2019 issue of the online journal Ecosphere.
The authors glued codling moth cocoons to walnut tree trunks and covered some with cages that exclude birds to test the effect that bird predation has on controlling moth pests. If moths emerge from cocoons, they produce larvae that feed on the nuts the following spring, causing significant and costly damage to the crop.
“Permitting bird access to cocoons during the wintertime increased codling moth predation from 11% to 46%, and predation increased with an increasing amount of natural habitat within 500 meters (one-third mile) of the orchard,” the researchers wrote.
Long was not surprised by the finding. She often walks in her family's almond orchard, where a large hedgerow of native California plants grows on the field edge.
“When I walk past the hedgerow,” she said, “I hear birds singing. I see white-crowned sparrows, goldfinches and mocking birds. It's so alive. It's really important to provide habitat to ensure birds have a place to live on farms.”
Songbirds are voracious predators of bugs, including aphids, whitefly, scale, caterpillars, ants and earwigs, especially early in the season when they are feeding baby birds.
Heath said they were surprised to find that the walnut orchards also provided habitat for birds. Woodpeckers and codling moth reduction were highest in orchards where big, old walnut trees were retained.
Currently, 34% of earth's arable land is managed for agriculture. With the human population projected to reach nearly 11 billion by 2100, increased food demand will require increased agricultural area and intensity that will further diminish birds' natural habitat. Providing habitat along field crop borders benefits songbirds, which in turn helps farmers with natural pest control on farms.
Above, a Nuttall's woodpecker eats an experimental codling moth (Cydia pomonella) larvae in a California walnut orchard. (Video: Sacha Heath)
Birds' suffer a reputation as agricultural pests. But Long said that planting hedgerows along field edges won't attract more pest birds.
Heath added, “Insect-eating birds – like chickadees, nuthatches and woodpeckers – move along hedges, riparian streams, old oak trees, and among crops to feed on pests.”
Maintaining hedgerows of native plants on farms has the side benefit of attracting natural enemies and native bees for better pest control and pollination in adjacent crops.
Long is a technical advisor to the Wild Farm Alliance, which, with Heath and Sara Kross, recently published a book on birds' role in pest management. The book, Supporting Beneficial Birds and Managing Pest Birds, is available for free download from the alliance's website. A recording of a webinar on the same topic can be viewed at eOrganic.
Heath is now a biodiversity post-doctoral fellow at the Living Earth Collaborative in Missouri.
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.
Farmers know they lose crops to pests and plant diseases, but scientists have found that on a global scale they are reducing crop yields for five major food crops by 10 percent to 40 percent, according to a report by a UC Agriculture and Natural Resources scientist and other members of the International Society for Plant Pathology. Wheat, rice, maize, soybean and potato yields are reduced by pathogens and animal pests, including insects, scientists found in a global survey of crop health experts.
At a global scale, pathogens and pests are causing wheat losses of 10 percent to 28 percent, rice losses of 25 percent to 41 percent, maize losses of 20 percent to 41 percent, potato losses of 8 percent to 21 percent, and soybean losses of 11 percent to 32 percent, according to the study, published in the journal Nature, Ecology & Evolution.
“We are losing a significant amount of food on a global scale to pests and diseases at a time when we must increase food production to feed a growing population,” said co-author Neil McRoberts, co-leader of UC ANR's Sustainable Food Systems Strategic Initiative and Agricultural Experiment Station researcher and professor in the Department of Plant Pathology at UC Davis.
While plant diseases and pests are widely considered an important cause of crop losses, and sometimes a threat to the food supply, precise figures on these crop losses are difficult to produce.
“One reason is because pathogens and pests have co-evolved with crops over millennia in the human-made agricultural systems,” write the authors on the study's website globalcrophealth.org. “As a result, their effects in agriculture are very hard to disentangle from the complex web of interactions within cropping systems. Also, the sheer number and diversity of plant diseases and pests makes quantification of losses on an individual pathogen or pest basis, for each of the many cultivated crops, a daunting task.”
“We conducted a global survey of crop protection experts on the impacts of pests and plant diseases on the yields of five of the world's most important carbohydrate staple crops and are reporting the results,” McRoberts said. “This is a major achievement and a real step forward in being able to accurately assess the impact of pests and plant diseases on crop production.”
The researchers surveyed several thousand crop health experts on five major food crops – wheat, rice, maize, soybean and potato – in 67 countries.
“We chose these five crops since together they provide about 50 percent of the global human calorie intake,” the authors wrote on the website. The 67 countries grow 84 percent of the global production of wheat, rice, maize, soybean and potato.
Top pests and diseases
The study identified 137 individual pathogens and pests that attack the crops, with very large variation in the amount of crop loss they caused. For wheat, leaf rust, Fusarium head blight/scab, tritici blotch, stripe rust, spot blotch, tan spot, aphids and powdery mildew caused losses higher than 1 percent globally. In rice, sheath blight, stem borers, blast, brown spot, bacterial blight, leaf folder and brown plant hopper did the most damage. In maize, Fusarium and Gibberella stalk rots, fall armyworm, northern leaf blight, Fusarium and Gibberella ear rots, anthracnose stalk rot and southern rust caused the most loss globally. In potatoes, late blight, brown rot, early blight and cyst nematode did the most harm. In soybeans, cyst nematode, white mold, soybean rust, Cercospora leaf blight, brown spot, charcoal rot and root knot nematodes caused global losses higher than 1 percent.
“Our results highlight differences in impacts among crop pathogens and pests and among food security hotspots,” McRoberts said. “But we also show that the highest losses appear associated with food-deficit regions with fast-growing populations, and frequently with emerging or re-emerging pests and diseases.”
“For chronic pathogens and pests, we need to redouble our efforts to deliver more efficient and sustainable management tools, such as resistant varieties,” McRoberts said. For emerging or re-emerging pathogens and pests, urgent action is needed to contain them and generate longer term solutions.”
The website globalcrophealth.org features maps showing how many people responded to the survey across different regions of the world.
In addition to McRoberts, the research team included lead author Serge Savary, chair of the ISPP Committee on Crop Loss, epidemiologists Paul Esker at Pennsylvania State University and Sarah Pethybridge at Cornell University, Laetitia Willocquet at the French National Institute for Agricultural Research in Toulouse, France, and Andy Nelson at the University of Twente in The Netherlands.