A survey of Lygus parasitoids in Sweden

Lygus spp. ( tarnished plant bugs) are generalist herbivores and occur as pests on a wide range of crops. In the development of conservation biological control strategies for Lygus spp. in Sweden, more information is needed on the impact of different natural enemies. In this study, we determined the occurrence and the degree of parasitism on adults and nymphs of the most common Lygus species in alfalfa, barley, red clover and oilseed rape in Uppsala in Central Sweden and in Umea in Northern Sweden. Nymphs and adults of Lygus spp. were collected by sweep netting for estimation of their parasitism level ( by dissection) and identification of parasitoid species ( from reared Lygus specimens). The dominant Lygus species in both locations was L. rugulipennis ( 75 - 99%). Parasitism by Phasia obesa ( Tachnidae) on overwintering Lygus adults was recorded in almost every field sampled at both locations. The parasitism level was low at overwintering sites but increased in arable fields during summer. Lygus nymphs collected in Umea were parasitised by Peristenus pallipes ( Braconidae) and in Uppsala by P. relictus, P. pallipes and P. varisae. The hyperparasite Mesochorus globulator ( Ichneumonidae) was recorded in Umea.