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Main Pests in the PNW
Potatoes are attacked by a large number of insects, including several which damage tubers in the field or storage. Foliar-feeding insects can be roughly divided into chewing, sucking or rasping types based on feeding techniques. Control measures may differ considerably among the three. Insecticides which provide good control for chewing insects such as the Colorado Potato Beetle, for example, may actually increase aphid populations due to adverse effects on aphid predator populations. Carbaryl (Sevin) and certain pyrethroids fall into this category. Applying such materials without an accompanying aphicide can lead to total crop losses due to aphids and viruses. A clear understanding of species controlled is an important aspect of any insect control program.
A number of good insecticides are available for potatoes. Some systemic types applied at planting or sidedressed post-emergence (Temik, Admire, Furadan, Thimet, Disyston) can provide good control of most insects for prolonged periods. Systemic insecticides are highly desirable in most situations because they are convenient to use, persistent, predator-friendly, and typically gentle to the environment. Soil-applied insecticides obviously are not subject to atmospheric drift onto non-target areas and have only mild, indirect effects on predators and other non-target species. As with nitrogen, care should be taken to minimize leaching of soil-applied pesticides by avoiding overirrigation at all times. Wireworms can be devastating if not controlled, especially following susceptible crops including some grasses. Control is typically achieved by broadcasting and incorporating insecticides such as Mocap and Diazinon either before or at planting. Unlike other Oregon producing areas, potatoes in the Willamette Valley are often severely damaged by the larval stage of the tuber flea beetle (as opposed to the potato flea beetle). Adult tuber flea beetles typically lay eggs near the base of the plant well into the growing season. Therefore, control is based largely on controlling the adults as necessary. Materials used for other important beetles affecting potatoes will also control the tuber flea beetle.
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