Effects of straw mulch, spent mushroom compost, and fumigation on the density of Colorado potato beetles (Coleoptera: Chrysomelidae) in potatoes

Abstract

Colorado potato beetle, Leptinotarsa decemlineata (Say), population trends were monitored in potatoes under different pest management and cultural regimes. Four cultural practices (straw mulch, spent mushroom compost, both mulch and compost, and conventional practices without mulch or compost) were used as subplots within main plots representing 3 pest management practices. In 1992, beetles were managed by hand removal until July, and the 3 treatments were removal without soul fumigation, no removal without fumigation, and no removal with fumigation. In 1993 and 1994, beetles were managed by use of insecticides, and the 3 treatments were insecticides with soil fumigation, insecticides without fumigation, and no insecticides with fumigation. Straw mulch reduced the density per square meter of adults and large larvae in plots without beetle management in 1992 and 1994, and the density of adults in insecticide-treated plots in 1993. Defoliation was lower in mulched subplots without beetle management in 1992 and 1994, and leaf area (1992) or ground cover (1994) was increased in these treatments, but yield was not affected. Compost increased leaf area and yield in 1992, and increased the density of adults and egg masses in that year, but generally had minor effects on beetle density and varying effects on yield. Fumigation significantly decreased yield in 1992 and 1994, and it had no effect on yield in 1993. Any benefits of fumigation in mitigating disease were offset by the earlier peak in density of large larvae in 1992, and the greater density of adults in 1993 and 1994 in fumigated plots compared with plots without fumigation.