Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/7/2004
Publication Date: 8/24/2004
Citation: Leland, J.E., Mcguire, M.R., Grace, J.A., Jaronski, S., Ulloa, M., Park, Y., Plattner, R.D. 2004. Strain selection of a fungal entomopathogen, beauveria bassiana, for control of plant bugs (lygus spp.) (heteroptera : miridae). Biological Control. Interpretive Summary: Strains of a fungus (Beauveria bassiana) obtained from tarnished plant bugs and western tarnished plant bugs are being evaluated as potential microbial control candidates for controlling these two plant bug pests. Based on initial work with a large collection of strains from both plant bug species, eight strains were evaluated for characteristics relevant developing commercial control products. These characteristics included lethality to the two plant bug species, potential for the strains to grow on media, temperatures at which fungal growth is optimal, survival under artificial sunlight, and production of toxic compounds. Comparisons were made with a commercial strain (GHA). Fungal strains from the two plant bug species caused higher mortality in these species than the commercial strain GHA. In many cases they cause over ten times more mortality. All strains from the two tarnished plant bug species grew slowly at 35 'C, whereas no growth was observed for the commercial strain. The isolates selected from western tarnished plant bug were the most tolerant to artificial sunlight. Strains from tarnished plant bug and western tarnished plant bug were most closely related to other strains from their same host species and all of these isolates were only distantly related to the commercial strain. Optimizing spore production conditions for a select strain may be necessary for practical development as a commercial product.
Technical Abstract: Beauveria bassiana (Balsamo) isolates from Lygus hesperus (Knight) and Lygus lineolaris (Palisot de Beauvois) are being evaluated as potential microbial control candidates for both Lygus species. Based on initial work with a large collection of isolates from both Lygus species, eight isolates were evaluated for characteristics relevant to mycoinsecticide development. These characteristics included pathogenicity to the two Lygus spp., in vitro conidia production, temperature growth optima, tolerance to solar radiation, and production of mycotoxins. Comparisons were made with a commercial isolate (GHA). Isolates from L. hesperus and L. lineolaris were more pathogenic than GHA with many being more than an order of magnitude more pathogenic based on LC50 values. All isolates from Lygus spp. grew slowly at 35 'C, whereas no growth was observed for GHA. The isolates selected from L. hesperus were the most tolerant to exposure to simulated solar radiation. Isolates from L. lineolaris and L. hesperus were most closely related to other isolates from their same host species and all of these isolates were only distantly related to GHA. Interestingly, one isolate from L. lineolaris in MS was more closely related to an isolate from L. lineolaris in AR than to other isolates from L. lineolaris from the same county in MS. Optimizing conidia production conditions for a select isolate may be necessary for practical development of a select isolate from Lygus spp. as a commercial mycoinsecticide.