Population Dynamics of Lygus hesperus(Heteroptera: Miridae) on Selected Weeds in Comparison with Alfalfa

Abstract

The effects of different early spring weeds on the population dynamics of the western tarnished plant bug, Lygus hesperus Knight, were examined under laboratory conditions. In cage experiments, adult Lygus bugs were placed onto 6 weed species and alfalfa, Medicago sativa L. Sutter'. Survival of adult bugs was generally lower on monocot weeds than dicot weeds. The lowest survival was on wild oats, Avena fatua L., at 6.6 d and greatest survival was on shepherd's purse, Capsella bursa-pastoris (L.) Medikus at 20.4 d. Survival on alfalfa was intermediate at 12.1 d. Lygus bug nymphal development and numbers of F 1 adults produced on each plant species were recorded. Foxtail barley, Hordeum jubatum L., produced no Lygus nymphs; among all other plant species no significant differences were found in nymphal development. Numbers of emerging F 1 adult Lygus bugs were greater on dicot weeds with the most produced on common chickweed, Stellaria media (L.) Villars, and common groundsel, Senecio vulgaris L. Fewer adult Lygus bugs emerged from monocots with none emerging from foxtail barley. These data indicate that foxtail barley is not a preferred host, and that all other plants tested were reproductive host plants for L. hesperus. Morphometric analyses of F, adult Lygus bugs recovered from the various plants indicated that overall bug size was not affected by food source. Ovipositional preference was determined by totaling the number of eggs laid into each substrate. In choice tests Lygus bug females preferred to oviposit into foxtail barley and common groundsel over all plant species tested.