Seasonal occurrence and abundance of the tarnished plant bug (Hemiptera :Miridae) and thrips (Thysanoptera : Thripidae) on rapeseed in WestTennessee

摘要

Plant bugs and thrips were sampled in seven commercial rapeseed fields in West Tennessee in 1990 and eight in 1991. Nine hemipteran species were identified from field collections and the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was the most abundant (>95%). Tarnished plant bug adults were collected on the first sampling dates each year (7 April 1990 and 10 April 1991). Both adult and nymphal L. lineolaris fed on buds, flowers and seedpods. In 1990, adult L. lineolaris densities were greatest when rapeseed began to ripen. Highest nymphal L. lineolaris densities occurred when rapeseed was fully ripened (stage 5.5). In 1991, both adults and nymphs were most abundant during late ripening stages. Three thrips species: flower thrips, Frankliniella tritici (Fitch), tobacco thrips, F. fusca (Hinds), and soybean thrips, Neohydatothrips variabilis (Beach) were collected. Flower thrips was the most abundant species collected in both:years. At most of the collection sites, densities of flower thrips were greatest within two weeks prior to rapeseed flowering cessation. West Tennessee is a major cotton-growing region, where L. lineolaris and thrips are fruiting- and seedling-stage pests, respectively. Therefore, if rapeseed were to be reestablished as a crop in Tennessee, L. lineolaris and thrips problems in cotton would likely increase as well.