Manage Pesticide Resistance

It’s high on the list of grower nightmares. An important and reliable pesticide suddenly stops working. More of the product is applied, but with unacceptable results. It’s a well accepted fact that sooner or later pests and diseases develop resistance to synthetic chemicals. Now what?

One answer is to switch products. Switching products may help, but the same dynamics are at play and the problem will likely reoccur. But there is another answer: Confound the pests with strategically timed applications of more complex chemistries.

Complex chemistry is the trademark of biopesticides, which have emerged as the number-one tool in helping growers combat resistance. Biopesticides help manage resistance in two ways. When a grower substitutes a biological for a conventional pesticide, pests and disease populations are no longer being exposed to the synthetic material they’re building resistance to. This extends the efficacy and lifespan of the grower’s most critical synthetic materials. Also, due to their complex chemical nature, pests and diseases do not easily build resistance to biopesticidal compounds.

Success In The Field

The most widely used biopesticides for resistance management are Bt- (Bacillus thuringiensis) based products, says Ramon Georgis, global business manager for Valent BioSciences Corp., Libertyville, IL. Bt is a naturally occurring microorganism in the soil. There are thousands of strains of Bt and a few have been used to manufacture microbial insecticides.

“Most of the Bts have multiple toxins. Therefore,” he points out, “the opportunity for an insect to build resistance in these types of products is very small compared to most of the chemical insecticides, including the new, reduced-risk insecticides, where, in most cases there is only one primary mode of action.”

As a biological insecticide, Bt is considered a true success story by Michael Dimock, director of technology & development for Certis USA, Columbia, MD. He works with products that have proven to make ideal orchard bloom sprays to control twig borer, without harming beneficial organisms such as honeybees, which are usually prevalent in orchards during bloom.

In tomatoes and leafy vegetable crops, Georgis says that Bt products are also very popular for controlling diamondback moth, loopers, and other pests. In one case, relates Georgis, a  reduced-risk chemical product was brought on the market to control these pests, but has since been pulled from certain states because diamondback moth quickly became resistant to it. “This is exactly why a Bt product fits ideally in a program with chemical insecticides to expand the life of the chemical insecticides and to minimize the opportunity for the insect to build resistance.”

Better yield and lower cost to growers have been consistently proven when Bt products are used in resistance management program with chemical insecticides. This is a valuable and important criterion for growers, Georgis said. The products have to work, and they have to be cost effective.

“The very worst insecticide approach is to find something that works and stick with it,” says Dr. David G. Riley, vegetable research entomologist at the University of Georgia, who specializes in resistance management of diamondback moth in brassicas. “And,” he adds, “if a product begins to fail, the very last thing to do is reapply the same product.”

The Search For Alternatives

Growers need alternative materials to supplement their crop protection programs.

Dr. John Trumble, a University of California (UC) Riverside professor of entomology and consultant to some of California’s largest fresh market tomato, celery, and pepper growers, says rotating biopesticides with synthetic chemicals is “absolutely critical.”

“We use biopesticides on a regular basis to break the cycle of harder chemicals and try to prevent resistance development,” he says. Trumble points out that the growers he consults are very receptive to using biopesticides because “they’ve been stung before by resistance development.”

For Trumble, the task of creating a viable rotation program is broader than just recommending crop protection materials. He conducts a cost analysis to determine how to economically rotate biopesticides into the program. “We set up a program and run an economic analysis to find out what the net return was for the compounds that were sprayed,” he explains. “That, to me, is the best way to get growers to do it. If a program doesn’t pencil out — show a return on investment — it makes no sense to participate.”

Another tool used by both Trumble and Riley is to follow the guidelines outlined by the Insect Resistance Action Committee (IRAC) — an arm of the industry association CropLife — to avoid using materials with similar modes of action which leads to resistance. Similarly, the Herbicide Resistance Action Committee (HRAC) and the Fungicide Resistance Action Committee (FRAC) have been organized to assist in combating resistance issues in weeds and diseases. 

“More and more, we are seeing bio-pesticides being put into conventional programs, and that’s what we’re targeting,” says Denise Manker, AgraQuest’s vice president of global development. “The goal,” she adds, “is that growers will have more tools longer because they won’t wear out the single-site fungicide.”

Resistance Management Using Biopesticides

The ability of biopesticides to extend the life of conventional products is rooted in the fact that pests and diseases don’t usually develop resistance to biological products themselves.

John Francis, director of marketing and technical services at BioWorks Inc, Fairport, NY, explains that most synthetic pesticides focus on a specific biological pathway or certain biological functions in the nervous system of an insect and, over time, insects or fungi develop resistance. “Initially the synthetic product works just fine,” he says, but in time, the pest just mutates around it.”

Unlike products based on synthetic chemistry which are usually comprised of a single compound, biopesticides have an active ingredient or formulation that is derived from biological or natural origins. They contain multiple active ingredients and, by extension, are less prone to resistance. Scientifically it’s incorrect to say resistance will never show up, but the occurrence is low.

The increase in use of biological materials is not limited to crop protection. Michael Braverman, manager, Biopesticide Program, IR-4 Project, Rutgers University, points out that biological materials have a wide variety of applications. As an example, he helped register thymol with EPA. Today, thymol has become a popular tool for beekeepers to control varrora mites in honeybees.

“The reason,” says Braverman, “is that the varroa mites were developing resistance to the conventional miticides.” Beekeepers have not reported mites developing resistance to the biological product.

It’s no secret that over time pests and diseases develop resistance to synthetic chemicals, but savvy growers and crop consultants are developing ways to combat the problem. Biopesticides continue to gain momentum as excellent tools to assist growers in keeping resistance under control without sacrificing efficacy or crop quality.

Leave a Reply

Featured Stories

All Vegetables Stories >All Fruits Stories >All Nuts Stories >All Citrus Stories >

The Latest

Apples & PearsKasumin Now Registered For Fire Blight Control
September 22, 2014
EPA approves use of bactericide on pome fruit as disease management tool. Read More
Food SafetyUSDA Issues Updates To Food Safety Modernization Act
September 19, 2014
Water testing, definition of applicable farms based on produce sales among clarifications to proposed rules. Read More
GrapesThird Straight Record Crop For Washington Grapes
September 19, 2014
Numbers expected to climb as more vines planted in the state. Read More
GrapesFrench Winegrowers Face Higher Labor Costs
September 19, 2014
French wineries may come under added financial pressure as the government considers imposing social charges on wages paid to harvest workers with short-term contracts. Read More
IrrigationCalifornia Boosts Local Water Control
September 19, 2014
Governor Jerry Brown signs historic legislation to strengthen local management and monitoring of critical groundwater basins. Read More
VegetablesSakata Seed America Shows Heart Through Charitable Prog…
September 19, 2014
Company’s corporate giving mission bears fruit for the American Heart Association. Read More
Insect & Disease UpdateAdditional Aid Coming For Florida Citrus Growers Gouged…
September 17, 2014
Through USDA’s Tree Assistance Program, eligible growers can cash in on cost share for diseased tree removal and replanting. Read More
FruitsFlorida Fruit & Vegetable Association Seeks Fresh A…
September 17, 2014
New partnership bolsters Fresh From Florida program. Read More
CitrusFDA Announces Cooperative Agreement To Implement Nation…
September 17, 2014
Agreement will provide information to help plan and carry out the produce safety rule in partnership with state regulatory agencies. Read More
NutsAchieving A Super-Premium Walnut Crop
September 17, 2014
What are the best ways to get high quality walnuts that are light in color and fully developed? Read these 8 harvest best practices to find out. Read More
NutsAlmond Growers Highly Dependent On Groundwater
September 17, 2014
Fully 87% of large growers use groundwater to irrigate their trees. Read More
NutsWarm Winter And Drought Casting Doubt On Pistachio Harv…
September 17, 2014
Though Rabobank report says that one billion pounds still attainable by 2019. Read More
Crop ProtectionBagrada Bug On The Move In California
September 16, 2014
Find out more on management tactics and what counties are impacted by this invasive pest. Read More
Cucurbits14 Stand-Out Melon Varieties [Slideshow]
September 15, 2014
Browse the slideshow below for information on these exceptional melon varieties from the nation’s leading seed breeders and distributors. Read More
Grower Achievement AwardView Highlights From The 2014 United Fresh Washington P…
September 15, 2014
Browse this slideshow to view photos from the 2014 United Fresh Washington Public Policy Conference, including pictures of this year’s Grower Read More
Apples & PearsCanneries Hope To Encourage Growers To Grow Pears For P…
September 15, 2014
Higher wholesale prices offered as means to boost canning pear acres. Read More
FruitsDeadline Nearing For Noninsured Crop Disaster Assistanc…
September 15, 2014
Fruit growers who suffered losses due to frost or freeze in 2012 could be eligible for assistance through USDA’S Farm Service Agency. Read More
BerriesBotrytis Gray Mold Pressure Increasing With Humid Weath…
September 15, 2014
Michigan State University researcher offers tips to reduce the spread of spores. Read More