Arms Race

BioSafe's new biological is just one of the latest innovations in the management of Colorado potato beetle.

Published online: May 03, 2018 Insecticide
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This article appears in the May 2018 issue of Potato Grower.

In the 2015 film The Martian, Matt Damon played Mark Watney, an astronaut who becomes stranded on Mars and must overcome an overwhelming list of obstacles to survive. (Don’t worry, I’m not giving any spoilers.)

Those of us in the industry who enjoy seeing potatoes placed strategically in a movie can remember vividly that iconic moment in the film when Watney successfully cultivates on the surface of Mars one of Earth’s oldest and most trusted food sources—the potato! Those who saw the movie remember the relief they felt for the stranded astronaut as he celebrated the sprouting of his first potato crop, at one point poignantly stating, “I don’t want to come off as arrogant here, but I’m the best botanist on this planet.” It didn’t take long for astronaut-turned-potato grower to eat his words, watching his entire potato crop go from thriving to dying in the blink of an eye after a disaster destroys his crop.

Yes, I’m grasping at straws and taking dramatic liberties to create a relevant story on the “trials and tribulations” of growing a healthy, quality potato crop, but there’s a lot of truth behind what Watney experienced and what earthling potato growers experience season to season. At the end of the day, the good Lord and Mother Nature will always ensure growing any crop, especially potatoes, will never occur without trials and tribulations.

Mark Watney did have one advantage over earthling potato producers: He didn’t have to manage a wide range of pathogen and pest pressure that have plagued potato growers across the globe. One little critter that has become the most invasive and devastating insect pest to ever affect potato production across the globe has been making headlines recently: the Colorado potato beetle.

 

Why So Devastating?

The most challenging trait of the Colorado potato beetle is its ability to develop rapid resistance to conventional insecticide programs. The species can develop rapid resistance thanks to a variety of biological mechanisms, including enhanced metabolism, target site insensitivity, reduced insecticide penetration and increased excretion of toxins. Many conventional insecticides have shown rapid reduction in efficacy, with different Colorado potato beetle populations around the globe developing documented resistance to an estimated 56 different conventional insecticides compounds. A few examples of common chemistries against which Colorado potato beetles have exhibited resistance include carbamates, organophosphates, synthetic pyrethroids/pyrethrins and neonicotinoids.

What may be the scariest yet most impressive adaptation is the beetles’ perceived development of behavioral resistance, which researchers are still striving to understand in order to develop best practices to provide multiple methods of prevention.

As of today, resistance management practices are the most critical tool for effective control of Colorado potato beetles. These practices require a combination of cultural, biological and chemical strategies to maintain consistent management of larval and adult populations. The first step in preventing mass outbreaks in production fields is pest monitoring and establishing thresholds based on local extension guidelines in respective regions, with many educational resources suggesting chemical application when thresholds reach 15 adults, 75 small larvae or 30 large larvae per 50 plants. Several cultural controls can be employed and have proven effective in reducing Colorado potato beetle incidence and severity. These include crop rotation, use of mechanical barriers, early or late planting, and utilization of trap crops.

 

Crop Protection Innovations

New tools and strategies are being developed through the collaboration of university researchers, innovative growers and bio-rational manufacturers. Some of these new tools are showing promising results when incorporated into integrated pest management programs for Colorado potato beetle. Mycoinsecticides like Beauveria bassiana or botanical insect growth regulators made with plant extracts such as azadirachtin are gaining traction in the fight.

The Beauveria bassiana fungus, specifically the ANT-03 strain utilized in BioCeres mycoinsecticide, has shown replicated in-field trial results showing up to 80 percent reduction in larvae and 75 percent reduction in adult beetles. This unique strain of Beauveria bassiana infects beetles through direct contact with fungal spores, ingestion of treated host foliage, and transfer from one beetle to another. Beauveria bassiana conidia aggressively release additional spores into the field environment, helping provide control of larval and adult beetles throughout most of the season. In addition, studies have shown synergistic properties between Beauveria bassiana and imidacloprid, providing increased efficacy against multiple instar stages and adults. Although trials are still being conducted on additional synergy between the Beauveria bassiana strain and other traditional insecticides, the ANT-03 strain has proven to be highly aggressive on Colorado potato beetles and is a powerful tool that has yet to show any resistance challenges.

Botanical insecticides and nematicides are a fantastic approach for controlling the early life cycle of Colorado potato beetles by acting as an insect growth regulator. Tests using a 3 percent concentration of azadirachtin (AzaGuard) have shown that it can help break up resistant populations of early larval stages and has shown synergistic properties when used in combination with biocontrols such as Beauveria bassiana and other conventional insecticides. Some studies have found that rotational sprays of Azadirachtin-based insecticides and Bt (Bacillus thuringiensis) have shown stronger efficacy against early larval stages than either product used individually; however, it was noted efficacy was strongest when azadirachtin was applied first, followed four to five days later with Bt.

There is no silver bullet product or approach to managing Colorado potato beetle in potatoes or any other affected crops. The only way to reduce crop losses from this pest is through a truly integrated approach to inhibit the further development of resistance. Growers must understand the enemy they’re battling and utilize a multi-attack strategy, rotating different insecticide groups and incorporating non-chemical cultural practices into an integrated pest management program.

We’ve all heard it before, and it’s been repeated time and time again, but it remains the No. 1 piece of educational advice to help growers prevent Colorado potato beetle infestations: An ounce of prevention is likely to be worth a pound of cure.