Variation of Lygus species assemblages in canola agroecosystems in relation to ecoregion and crop stage

Abstract

AbstractPlant bugs in the genus Lygus (Hahn) (Hemiptera: Miridae) are sporadic pests of canola, Brassica napus L. (Brassicaceae) and Brassica rapa L., in western Canada and infestations appear to have become increasingly common and severe in recent years. Surveys conducted from 1998 to 2000 identified a "northern" assemblage in the boreal ecoregion that was dominated by Lygus lineolaris (Palisot de Beauvois), with minor representation of Lygus borealis (Kelton), Lygus elisus (Van Duzee), and Lygus keltoni (Schwartz). A "southern" assemblage in the grassland ecoregions was dominated by L. keltoni, with a substantial abundance of L. elisus and L. borealis and with few L. lineolaris in the driest areas. The assemblage from the parkland ecoregion was variable but with few L. elisus. The boreal plains and parkland ecoregions of Alberta had the most serious and persistent infestations of Lygus spp. Relative species composition of the Lygus assemblage at the bolting stage was not related to the overall abundance of these bugs at the early pod stage. Lygus species assemblages were similar in terms of composition and relative abundance at the bolting and early pod stages of canola. A shift in species proportions in favour of L. lineolaris in the north and L. keltoni in the south and a decrease of L. elisus has taken place relative to studies conducted in the 1980's.