Colorado potato beetle, potato leafhopper, and wireworms remain some of the most important insect pests of potatoes. In 1996, the first neonicotinoid insecticide, imidacloprid (Admire, Bayer CropScience) was registered for use on potatoes in the U.S., and a few years later, other neonicotinoids, including thiamethoxam, acetamiprid, dinotefuran, and clothianidin would
Since that period, neonicotinoids have been the most commonly-used insecticides on potatoes for control of Colorado potato beetle (CPB) as well as other pests such as potato leafhoppers, aphids, and flea beetles. Although they are effective as contact foliar insecticides, it is the ability of these chemicals to translocate from the soil into leaves as systemic insecticides that has been one of the primary reasons for their popularity.
Most potato growers apply these chemicals at planting (Admire Pro, Bayer CropScience; Platinum, Syngenta Crop Protection; Belay and Venom, Valent U.S.A.; Scorpion, Gowan Co.; or Brigadier, FMC Corp.) or as a pre-planting treatment to seed pieces (such as Cruiser, Syngenta Crop Protection; Gaucho, Bayer CropScience; or Admire Pro). Both application methods have been shown to provide long-term (more than 60 days) systemic protection to the potato plant against CPB and potato leafhopper. Most neonicotinoids also provide significant suppression of wireworms that attack the potato seed pieces.
These products have worked well, but insecticide resistance to neonicotinoids has appeared in numerous populations of CPB from the Northeast and Midwest. Managing neonicotinoid resistance in CPB through IPM practices and rotation of insecticide active ingredients is key to sustaining the long-term efficacy of these compounds for potato producers.
Fortunately there are a wide range of registered insecticides today that provide excellent control of CPB and other pests, including Radiant and Blackhawk from Dow AgroSciences; Coragen from DuPont Crop Sciences, and the newly labeled Verimark for soil applications and Exirel for foliar applications both also from DuPont; Voliam Xpress and Agri-Mek from Syngenta Crop Protection; and Rimon from Chemtura Corp.
Many of the alternative chemicals are more IPM-friendly control options that are safer to use around beneficials than the more traditional broad-spectrum organophosphates, carbamates, or pyrethroids.
In the true sense of IPM, however, potato growers would not use a preventive control, such as a treatment on seed pieces at planting or spray application. Instead, they would wait until confirming the pest’s presence in the field.
Even though many growers do not want to wait until they see CPB in their fields, there are growers in Virginia who are beginning to adopt IPM tactics and are scouting first and applying a control measure once they see signs of the pest.
What some growers fail to fully understand, though, is that potato plants can withstand some level of defoliation and applying an insecticide immediately may not be necessary. This fact often is a hard sell as most growers simply do not want any sign of CPB in their fields.
Insect Pressure Challenges
CPB pressure is often determined by location and can vary widely. For example, growers in New England and the Pacific Northwest have some CPB pressure but not like the pressure levels in the Mid-Atlantic and Southern states, especially when the temperature begins to rise.
As a result the New England and Pacific Northwest growers may have better success employing IPM tactics. For example, one IPM practice is to only treat potato field perimeters with a crop protectant. The expected outcome is that the beetles will be killed as they walk along field edges, unable to harm the potato plants inside the perimeter.
What isn’t taken into consideration, however, is that as the temperature climbs to 80°F and above, in Southern states rising temperature is conducive for the beetles to take flight. The bottom line: They aren’t walking through the perimeter of the field to get to the potato plants. They are flying in, making the perimeter sprays moot.
In the end, growers need to determine what will work best for them based on their location in the country. They must consider neonicotinoids as one tool in the tool box, and opt to rotate with other chemistries to avoid resistance issues.
Editor’s Note: The information for this article was contributed by Tom Kuhar ([email protected]), a professor in the Department of Entomology at Virgina Tech and is based on a presentation he gave at the 2014 Mid-Atlantic Fruit & Vegetable Convention.