Resistance Isn’t Futile — It’s Manageable

It’s high on the list of grower nightmares. An important and reliable pesticide suddenly stops working. 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. That may help, but the same dynamics would be 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.

"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."

Growers need alternative materials to supplement their crop protection programs.

Dr. John Trumble, a University of California-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 biopesticides 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

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, N.Y., says 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. 

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, Ill. 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," he points out. "Therefore, 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, Michael Dimock, director of technology and development for Certis USA, Columbia, Md., considers Bt a true success story. 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. By using Bt, the grower achieves the necessary level of pest control, protects the beneficial insects living in his orchard and limits the amount of conventional chemistry being applied.

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

In greenhouses, biological fungicides have also proven successful for flower growers. In the case of Easter lilies and poinsettias, Francis points out, specific biopesticides have done a very good job controlling pythium root rot, fusarium and rhizoctonia. If a grower is unsure about the health of his cuttings or in cases where disease inoculum gets very high, he recommends coming in with a chemical fungicide drench on the whole crop or just the hot spots, then applying the biologicals. Often, if the cuttings are healthy, no synthetic chemical sprays are needed at all.

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 the Environmental Protection Agency. 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.

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

Latest Stories
Pennisetum Fireworks

April 28, 2016

Why Ornamental Grasses Are Great For People In Condos A…

Allan Armitage says breeders need to do a better job of making growers, brokers, and garden centers aware of better ornamental grass cultivars for the increasingly shrinking garden space.

Read More

April 28, 2016

Holistic, Integrated Approach To Pest Control Rooted In…

Greenhouse growers have been practicing integrated pest management for decades, but it’s becoming increasingly more important with the continued scrutiny of conventional pest control by a number of “regulators” — government, retail, and consumers. I just returned from Meister Media Worldwide’s Biocontrols USA 2016 Conference, in Monterey, CA, at the beginning of March this year, which served 450 attendees and 50 exhibiting supplier companies. It’s clear from the presentations and the growing attendance at this specialized event — now only in its second year — that use of biocontrols in IPM will continue to be adopted widely, as more growers get past their personal hurdles of doubt and intimidation, and embrace a new way to approach pest and disease control. Many growers think of using biocontrols as an all-or-nothing approach, but ultimately, IPM is about balance. Growers will need to continue to focus on IPM, integrating chemistry with biology, because […]

Read More
Drip irrigated citrus liner

April 27, 2016

Unclog Drip Emitters In Your Greenhouse

This is the first article in a series of case studies designed to help growers reduce, remediate, and recycle irrigation water as part of a multi-state research grant (CleanWateR3.org).

Read More
Andropogon gerardii Blackhawks (Intrinsic Perennial Gardens)

April 27, 2016

Know Your Market When Choosing Ornamental Grasses

Growers have no shortage of choices in the ornamental grass market. Narrowing down the selection comes down to finding the right plant for the right purpose.

Read More
Fine Americas Website Feature Image

April 26, 2016

Fine Americas Offers A Digital Resource For Plant Growt…

The blog section of Fine America’s website is updated regularly, with input from both technical managers and independent researchers

Read More

April 26, 2016

“Bee-Friendly” Labels Matter To Plant Consumers, Accord…

Research at Michigan State University shows ornamental plant buyers understand and respond to bee-friendly production practices.

Read More
Cicada (Greg Hoover, Penn State)

April 26, 2016

Cicadas Set To Emerge In Several Eastern States This Sp…

While there’s no immediate cause for alarm, experts say the cicada’s egg-laying process can damage woody ornamentals and make them vulnerable to diseases.

Read More

April 26, 2016

How To Host A Spectacular Farm Dinner

Farm-to-table dinners are a great way to connect your customers with a love for nature and growing things. These three green industry companies have had a lot of success with their farm dinners. Find out what it takes to pull one of these dinners off successfully. Advice from Tangletown Garden’s Dean Englemann: You have to be certain you’re matching the ticket price to the experience, make sure you’re exceeding expectations. It can’t just be about the food. You have to deliver the experience. For us, we want to make sure there’s a lasting experience of connecting our food to families and dining. For lack of a better comparison, we want sitting in a field, eating food we grew and created, to be a religious experience. There’s almost a ceremonial aspect to these dinners. We’ve always thought that the shortest distance between the earth and people is the distance between the hand and the […]

Read More

April 26, 2016

Fun Display Ideas From California Spring Trials

In a year that was light on new introductions, plant breeders ramped up their display creativity. Garden retailers can find a lot of inspiration for their own stores here!  

Read More

April 26, 2016

12 Questions To Test If Your Store Is New-Customer Frie…

Consultant Ian Baldwin offers ways to help you look at your store with fresh eyes and how you can make it welcoming for new gardeners.

Read More
University of Florida Online Greenhouse Training Courses

April 25, 2016

University of Florida Offering Online Training Courses …

There will be five courses offered, with the first starting on May 30. Courses are available in both English and Spanish and range from beginner level to advanced education.

Read More
Bee on Bidens

April 25, 2016

Breeders Go The Distance To Bring New Plant Varieties T…

Breeders are meeting the demand for new varieties that perform and sell well by extending trialing to engage the grower community, using advanced technology, and encouraging international collaboration.

Read More
Parisitic Wasp Aphidius colemani

April 25, 2016

Plant Growth Regulator Use Can Affect Biological Pest C…

The use of plant growth regulators may negatively influence the outcome of biological control programs, according to researchers at North Carolina State University.

Read More
HGTV_2015CAST

April 24, 2016

9 Business Predictions Smart Brands Should Pay Attentio…

Andreas von der Heydt, Director of Kindle at Amazon, recently predicted what smart businesses will do in 2016 to strengthen their brands and promote their products.

Read More
North American greenhouse 1

April 23, 2016

Light Matters In Greenhouse Structures

The design of your greenhouse structure, in terms of light transmission, can have a powerful impact on your bottom-line profits.

Read More
Lin Schmale 1996

April 23, 2016

SAF’s Lin Schmale Offers Lessons From An Industry…

Schmale represented the floriculture industry on Capitol Hill for more than 20 years. The advocate has recently retired, and shares some valuable insights from her career.

Read More
Beneficial Insectary Orius insidiosus

April 22, 2016

Beneficial Insectary Increasing Production Of Three Bio…

The company is now producing Orius insidiosus, Dalotia coriaria, and Dicyphus hesperus at its California facility, reducing the transit time of perishable biocontrols between producer and grower.

Read More
Scott Schaefer Aris CEO

April 22, 2016

New Aris CEO Scott Schaefer Looks Forward To Dealing Wi…

Schaefer, who has been with Aris for 15 years, grew up working at his family’s greenhouse operation in Illinois.

Read More
[gravityform id="35" title="false" description="false"]