Strain selection of a fungal entomopathogen, Beauveria bassiana, for control of plant bugs (Lygus spp.) (Heteroptera: Miridae)

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 previous 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 beauvericin. 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 L. hesperus and two from L. lineolaris grew faster at 32 °C than 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 Mississippi was more closely related to an isolate from L. lineolaris in Arkansas than to other isolates from L. lineolaris from the same county in Mississippi. 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.