Abundance and parasitism of Lygus lineolaris in Alfalfa and strawberry fields

Lygus lineolaris (Heteroptera: Miridae) adults and nymphs were collected weekly from April to September in 2000 and 2001 from three alfalfa fields in central Iowa. From mid-May to June each year, L. lineolaris were also collected in three strawberry fields. In 2000 and 2001, patterns of seasonal abundance of L. lineolaris were similar at two of the three alfalfa sites. When the alfalfa was cut the number of L. lineolaris declined. In strawberries, the number of L. lineolaris decreased after the fruits had formed. Peak populations in 2001 (20 L. lineolaris per 20 sweeps) were approximately 2.5 times the population in 2000 (8 L. lineolaris per 20 sweeps). No parasitoids were reared from L. lineolaris collected from strawberries in either year. In 2000, four unidentified parasitoid cocoons and one parasitoid larva were reared from 1326 L. lineolaris collected in alfalfa (seasonal parasitism = 0.3%). The entomopathogenic fungus Beauveria bassiana (Hyphomycetes: Moniliales) infected one adult L. lineolaris collected in September 2000. In 2001, 42 unidentified parasitoid larvae and six cocoons were observed from 1267 dissected or reared L. lineolaris individuals (seasonal parasitism = 4%).