Colorado Potato Beetle (Coleoptera: Chrysomelidae) Population Development and Effects on Yield of Potatoes With and Without Straw Mulch

Colorado potato beetle, Leptinotarsa decemlineata (Say), population trends were monitored in potatoes, Solanum tuberosum L., grown in plots with and without straw mulch during 1988 and 1989 growing seasons in Virginia. An insecticide treatment was incorporated into a factorial experimental design (mulch × insecticide) in 1989 to evaluate effects of mulch on potato yield without Colorado potato beetle defoliation. Numbers of overwintered adult beetles, egg masses, and larvae were significantly lower in plots with mulch compared with those without. Soil temperature and moisture conditions were more favorable for potato plant growth in Virginia under straw mulch than in bare ground (no mulch) plots. Final tuber yields were significantly greater in mulched plots (with and without insecticides) compared with plots without mulch in both years of the study. Application of insecticides in 1989 also resulted in higher yields within each mulch treatment. In plots treated with insecticides, six spray applications were required to control Colorado potato beetle populations above economic thresholds in plots without mulch, compared with two applications in plots with mulch. The feasibility of the use of straw mulch in commercial potato production is discussed.