Isolation and evaluation of Beauveria bassiana (Deuteromycotina : Hyphomycetes) for the suppression of the glassy-winged sharpshooter, Homalodisca coagulata (Homoptera : Cicadellidae)
The glassy-winged sharpshooter, Homalodisca coagulata (Say) (Homoptera: Cicadellidae), is a significant threat to California agriculture as a vector of the bacterium, Xylella fastidiosa Wells, causative agent of Pierce's disease. Control strategies target vector populations to prevent the spread of the bacterium. One of the potential means of controlling H. coagulata is the use of entomopathogenic fungi. To discover naturally-occurring fungal pathogens that are adapted to H. coagulata and its habitats, soil samples from organic citrus and conventional pomegranate orchards in Tulare and Riverside counties in southern California were screened for the presence of pathogens. Using a modified Galleria bait method that required small quantities of soil, 124 isolates of Beauveria bassiana (Balsamo) Vuillemin and four isolates of Metarhizium anisopliae (Metschnikoff) Sorokin (Deuteromycotina: Hyphomycetes) were recovered. Additionally, 22 isolates of B. bassiana were recovered by plating soil suspensions on selective growth media. Natural fungal infections were not detected in H. coagulata populations from periodic sampling in Kern, Riverside and Ventura counties in southern California. Some of the B. bassiana isolates recovered from soil and other insect hosts in southern California were evaluated against H. coagulata along with those isolated from H. coagulata in Texas and Mississippi. Growth of the selected isolates also was evaluated at 15, 23, 28 and 32 degrees C. The Texas isolate and two California isolates of B. bassiana were virulent against H. coagulata and warrant further study.