Dale Spurgeon and Neal Hudson. USDA, ARS, WICSRU, Shafter Res. & Ext. Center, 17053 N. Shafter Avenue, Shafter, CA 93263
Lygus hesperus, a key pest of cotton in western production regions, is attacked by the naturally-occurring pathogen, Beauveria bassiana, in the San Joaquin Valley of California. Previous research at USDA-ARS, Shafter, CA sought Beauveria strains that were effective under high summertime temperatures typical of the region. However, the most appropriate use of Beauveria against Lygus in California cotton may not be as a rescue treatment. Alternatively, Beauveria may be useful in efforts to suppress overwintering populations of Lygus if strains are available that are highly virulent at low temperatures. We conducted preliminary laboratory trials of Beauveria activity against Lygus at temperatures of 75, 65, and 55 degrees F. High levels of infection were obtained with Beauveria isolates at all temperatures tested, and no differences among isolates were observed at the lowest temperature. Temporal patterns of mortality varied with temperature, and appropriate time intervals for assessing mortality were determined to be about 14, 21, and 28 days for temperatures of 75, 65, and 55 degrees F. Results provide a rationale for more detailed investigations of low-temperature activity of Beauveria against Lygus, and illustrate the need for additional information regarding the sites and mechanisms involved in Lygus overwintering in the San Joaquin Valley.
