Parasitization of beet leafhopper eggs, Circulifer tenellus, in California

Abstract

AbstractParasitoids attacking eggs of beet leafhopper, Circulifer tenellus (Baker) (Hemiptera: Cicadellidae), were surveyed at eight sites in southern and central California for 2 years. One site was an insecticide‐free sugar beet field, and the remaining sites were all uncultivated and supported weedy vegetation. At each site, host plants of beet leafhopper were collected and stored until parasitoids emerged from the leafhopper eggs in the vegetation. Vegetation samples included both naturally occurring host plants and sugar beet outplants that were first infested with beet leafhopper eggs in the laboratory and then placed in the field for 2 days. Parasitism generally was highest in summer and lowest in winter. Beet leafhopper eggs were parasitized by the mymarids (Hymenoptera: Mymaridae) Anagrus nigriventris Girault, Polynema eutettexi Girault, P. longipes (Ashmead), Polynema sp., Gonatocerus capitatus Gahan and two Gonatocerus spp. from the litoralis species group, and the trichogrammatids (Hymenoptera: Trichogrammatidae) Aphelinoidea zarehi Triapitsyn, Walker and Bayoun, A. turanica Trjapitzin, A. roja Triapitsyn, Walker and Bayoun, A. anatolica Nowicki and Paracentrobia sp. near P. subflava (Girault). The most dominant were A. nigriventris, A. zarehi and Paracentrobia sp. The intensity of parasitism varied greatly among the sites with peak levels ranging from 13% to 82%. Species composition also varied among sites, especially between the sugar beet field where A. nigriventris was by far the most dominant parasitoid and the uncultivated sites where A. zarehi and/or Paracentrobia sp. usually dominated. Within the uncultivated sites, parasitoid species composition also varied between the sugar beet outplants and the naturally occurring vegetation; A. nigriventris was much more common in the former than in the latter.