Assessment of Insect Emigration from Alfalfa Hay to Bean Fields

Abstract

Populations of five insect species— Lygus hesperus (Knight); the western flower thrips, Frankliniella occidentalis (Pergande); the pea aphid, Acyrthosiphon pisum (Harris); a damsel bug, Nabis americoferus (Carayon); and the minute pirate bug, Orius tristicolor (White)— increased slightly in bean fields after cutting of alfalfa hay. More definite increases of insects in bean fields occurred after hay cutting in 1978, when all hay study fields were cut on the same day, as opposed to 1979 and 1980, when adjacent hay fields were cut over a 10-day period. Proximity to a hay field did not correlate with large insect buildup in bean fields. No significant differences were recorded in numbers of these insects 10, 50, and 100 m into bean fields when adjacent hay fields were cut. Lygus bugs and thrips did not appear in beans in large numbers, and invaded beans only late in the growing season.