Pathogenicity of Isaria poprawskii (Ascomycota: Hypocreales: Cordycipitaceae) against the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae), under laboratory conditions

• Entomopathogenic fungi can control insect pests such as insect vectors of plant diseases.
• Isaria poprawskii, a new fungus species, was pathogenic against Homalodisca vitripennis.
• Virulence of I. poprawskii was different between conidia concentrations within each insect stage.
• Mycosis in sharpshooters occurs at 3–4 days and continues for 8–10 days.
• I. poprawskii can immobilize and stop insect feeding, which could slow the spread of Pierce's disease.

The pathogenicity of the newly discovered entomopathogenic fungus species Isaria poprawskii, found during epizootics on Bemisia tabaci (Gennadius) in the Lower Rio Grande Valley of Texas, was tested against the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) Takiya, under laboratory conditions (27 ± 1 °C; 75 ± 5% RH; photoperiod of 14:10 (L:D) h. Exposures of nymphs and adults to 500, 1000, and 2000 conidia/mm2 on cowpea, Vigna unguiculata (L.) Walp, leaves resulted in insect mortality. Median lethal concentrations for second- (685 conidia/mm2) and fourth-instar nymphs (771 conidia/mm2) were similar to those for adults (855 conidia/mm2). Virulence, as measured as mean time to death of the GWSS by survival analysis, was different between concentrations within each insect stage. For example, for the second-instar, I. poprawskii was more virulent at high concentrations (4.6 days) than medium (5.4 days) or low (5.5 days) concentrations. Mycosis in sharpshooters occurred at 3–4 days and continued for 8–10 days after spray. This fungus has the ability to immobilize and stop feeding on infected GWSS, which could potentially slow the spread of Pierce's disease. These results indicate that I. poprawskii is pathogenic to H. vitripennis nymphs and adults. Its pathogenicity and virulence against H. vitripennis show that this fungus is a promising biocontrol agent to control the glassy-winged sharpshooter.