Seasonal phenology and natural enemies of the squash bug (Hemiptera: Coreidae) in Kentucky.

The squash bug, Anasa tristis (De Geer), is a major indigenous pest of Cucurbita species across the United States and a vector of cucurbit yellow vine disease. The seasonal phenology of the squash bug in central Kentucky and its natural enemies were studied using summer squash planted sequentially throughout the 2005 and 2006 growing seasons. The squash bug was first detected on 5 June 2005 and 3 June 2006. In both years, peak numbers of all squash bug stages occurred in July and August. Our field data, substantiated by published degree-day models for squash bug development, suggest one complete and a partial second generation of squash bugs in 2005 and one complete generation of squash bugs in 2006. The most abundant ground-active predators in squash fields included Araneae, Carabidae, Staphylinidae, and Geocoridae. Coleomegilla maculata (De Geer) and Geocoris punctipes (Say) were the most abundant foliage-inhabiting predators. Direct field observations of predators feeding on squash bugs or their eggs included G. punctipes, Pagasa fusca (Stein), and Nabis sp. The parasitoids Trichopoda pennipes (Fabricius) and Gyron pennsylvanicum (Ashmead) were found also. Squash bug egg masses were monitored to determine predation and parasitism rates in the field. In four studies during 2005 and 2006, predation rates were low (7% or less), and parasitism ranged from 0 to 31%. Overall, squash bug egg mortality increased as the season progressed.