Pathogenicity of Beauveria Bassianna Strain NI8 on Lygus Lineolaris (Hemiptera Miridae) and Its Impact on Beneficial Arthropods

The virulence of Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales) strain NI8 was assessed on Lygus lineolaris (Palisot de Beauvois) and on beneficial arthropods including Apis mellifera L., Crysoperla rufrilabris Burmeister, Orius insidiosus Say, Hippodamia convergens Guérin-Méneville, Harmonia axyridis (Pallas), Coleomegilla maculata De Geer. Insects were treated with four concentrations of NI8 (7 x 10⁴, 10⁵, 10⁶ and 10⁷ spores/ mL) directly via topical spray. LD₅₀ and LS₅₀ were estimated for all species except for the collective field samples of jumping and crab spiders. From the resulting data, no significant differences in mortality were observed among L. lineolaris, A. mellifera and C. rufilabris. All three species were highly affected when exposed to the highest test concentrations of B. bassiana with 99.0%, 98.2%, and 90.0% mortality, respectively. Between 35 and 45% of the tested populations of O. insidiosus, H. convergens, field collected crab spiders, and C. maculata were infected at 7 x 10⁷ spores / mL; whereas only 22% and 27%, respectively of the field collected jumping spiders and H. axyridis were killed at 10-d with the same concentration. No significant differences were found between the LD₅₀s measured for L. lineolaris (2.75 viable spores per mm²) and C. rufilabris (2.11 viable spores per mm²). Higher LD₅₀ was needed for A. mellifera (43.45 viable spores per mm²), 652-fold greater than LD₅₀ needed for L. lineolaris was needed for H. convergens and LD₅₀s much greater than that were needed for the rest of the species. Results indicate that C. rufilabris will be highly affected by the NI8 strain of B. bassiana when applied for control of L. lineolaris. In contrast, B. bassiana appeared to have little to limited effects on the other beneficial arthropods assayed at the test concentrations targeted for L. lineolaris control.