Potato Grower

36 POTATO GROWER | NOVEMBER 2017 Diggin' In Diggin' In Diggin' In Diggin' In Diggin' In Diggin' In INSECTS | By Andrei Alyokhin, Professor of Applied Entomology, University of Maine Mitigating the consistent threat posed by Colorado potato beetles Death, Taxes and Beetles Colorado potato beetle is an insect that is undoubtedly very familiar to the readers of Potato Grower. Just as any other farming enterprise, producing potatoes is subject to myriad different forces, ranging from the amount of precipitation in the mountains 500 miles away, to political stability in the Middle East, to the latest diet fads sweeping throughout the United States and Canada, to behavioral problems plaguing yet another batch of politicians running for office. These are all highly variable, have a tendency to appear out of nowhere, often interact with each other in rather bizarre ways, and usually are impossible to predict with any degree of certainty. In such a context, a threat of Colorado potato beetle damage remains one of very few stable things in the life of a potato grower, right there along with death and taxes. Despite all human attempts to do something about them, these medium- sized and rather attractive-looking (at least to somebody who is not a potato grower) shiny insects seemingly always linger in the background. Although several chemicals are currently available to keep them at bay, they are always ready to start wreaking havoc as soon as something goes wrong with these compounds. Developing and improving insecticides has been the main focus of controlling Colorado potato beetles since the middle of the 19th century. The necessity of protecting potato crops from beetle damage was actually an important driver behind development of the modern agrichemical industry. The first major success story of using insecticides in agriculture was suppression of this pest in the Midwest in the 1860s through applications of Paris green (cuprous acetoarsenite). Furthermore, efforts to improve Colorado potato beetle control encouraged many important advances in pesticide application equipment, such as compression sprayers, air-blast sprayers, engine-operated sprayers and traction- operated dusters. By and large, the chemical approach was successful, as evidenced by the steady growth of potato yields. We have certainly come a long way since the times of Paris green and lead arsenate. Unfortunately, beetle populations did not remain static in the face of adversity, either. This species is characterized by a rather impressive adaptability to pretty much all the chemicals that have been thrown at it over the years. Although each new failure of a popular insecticide sometimes seems to be a great surprise to the parties involved (except, perhaps, the beetles), it is actually something to be expected. In nature, Colorado potato beetles specialize on eating plants in the nightshade family, of which potato is one representative. To protect themselves from herbivores, these plants produce high amounts of poisons in their foliage. As a result, Colorado potato beetles possess an array of enzymes designed to detoxify these phytochemicals inside their bodies. Tellingly, efforts to breed a potato resistant to beetle damage have been, so far, largely unsuccessful. Many detoxification enzymes, perhaps with some modifications, are also capable of destroying insecticides developed by humans. Simply put, Colorado potato beetle is not an easy organism to poison. Even when successful in killing target pests, insecticides are being constantly scrutinized for their effects on non-target organisms. Potential contribution of imidacloprid to worldwide decline in bees and other pollinators is one example of such a concern, and there are many others. Consequently, a particular chemical may be lost to growers not because of resistance development in insect populations, but because of its withdrawal from the market due to environmental considerations. End result to a grower, however, is the same. When our ability to poison Colorado potato

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