Abundance and Distribution of Lygus hesperus (Heteroptera: Miridae) in Two Conifer Nurseries in Western Oregon

Abstract

Seasonal patterns of Lygus hesperus Knight abundance and distribution were observed at two conifer nurseries in western Oregon during 1985. Lygus abundance differed significantly among conifer seedling types (age class/species combinations) and sampling dates. Highest densities were observed in lodgepole pine and ponderosa pine seedlings germinated during 1985, in Douglas-fir seedlings germinated in 1984 and in late July samples. Significant interaction between seedling type and sample date reflected a shift in Lygus occurrence among seedling types during the growing season, especially from 1984 Douglas-fir seedlings early in the season to 1985 seedlings later in the season. This shift coincided with dispersal of the first Lygus generation and with pruning of the 1984 seedlings for height control. These results indicate that L. hesperus abundance and distribution in conifer nurseries result from Lygus phenology in combination with seasonal changes in the spatial pattern of available resources. Implications for nursery management are discussed.