Occurrence and larval development of noctuid pests on potatoes in Eastern Washington

Caterpillars of a number of moth species can infest and defoliate potato plants, causing economic damage, primarily through loss of plant vigor. These defoliators include some cutworms, loopers, and armyworms of the Noctuidae. There is little or no information on the abundance, pattern of occurrence, economic thresholds, or host suitability of these pests. Our goals are to determine when these species occur in Washington potato fields, the composition of the species in those fields, and the development of the larvae on potato foliage. We will present data from 2009 and 2010 field sampling and laboratory assays. Results of the laboratory assays of caterpillars fed potato foliage and field species composition data highlight the potential threat certain species pose. Spotted cutworm, Xestia c-nigrum (Linnaeus), and cabbage looper, Trichoplusia ni (Hübner), developed well on all potato varieties evaluated and constituted a majority of the larvae found in potato fields. Other species either were not found in the field or did not perform well on potato foliage. Using a variety of sampling techniques, efforts to trap adult moth species of concern was a success. From this data we see that June flights of spotted cutworm moths are important contributors to caterpillars feeding on potato fields in July. This research will provide growers with better information on which species are a problem, how to detect them, and timing of pesticide applications for maximum benefit.