Weed Sources of Lygus Bugs in the Yakima Valley and Columbia Basin in Washington1

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Abstract
Collections of lygus bugs, mainly Lygus hesperus Knight and L. elisus Van Duzee, were made at weekly intervals in the lower Yakima Valley and Columbia Basin in Washington from weed hosts and alfalfa. Early in the season the crucifers, hoary cress, Cardaria draba (L.) Desv., tumble mustard, Sisymbrium altissimum (L.), and flixweed, Descurainia sp., are the primary hosts. Pepperweed, Lepidium latifolium L., and Russian thistle, Salsola kali L., are common mid-season weed hosts. Lambsquarters, Chenopodium album L., kochia, Kochia scoparia (L.) Schrad., marsh-elder, Iva xanthifolia Nutt., pigweed, Amaranthus retroflexus L., and ragweed, Ambrosia artemisiifolia L., are major reproductive sites in late season and host the potential overwintering populations. When a disturbed site, e.g., ditch bank, roadside, or field edge, returns to some degree of ecological stability with a grass cover, the pioneer species of weeds frequented by the lygus bugs cannot compete with the natural grasses, and lygus populations are markedly reduced.