Beauveria bassiana Activity Against Lygus hesperus at Low Temperatures.

Authors: Spurgeon, Dale; Hudson, Neal

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/8/2008
Publication Date: 5/15/2008
Citation: Spurgeon, D.W., and Hudson, N.D. 2008. Beauveria bassiana Activity Against Lygus hesperus at Low Temperatures. Proc. Beltwide Cotton conf., National Cotton Council, Memphis, TN. pp. 1316-1321.

Interpretive Summary: The western tarnished plant bug is an important pest of cotton in production regions of the western U.S. This pest is difficult to manage in cotton because it is highly mobile, feeds on a wide variety of plants, is difficult to sample accurately, and chemical sprays for its control often result in problems with other insect or mite pests. Beauveria bassiana is a disease that attacks plant bugs, and it occurs naturally in the San Joaquin Valley of California. Previous research at Shafter, CA sought strains of Beauveria that were effective under high summertime temperatures typical of the region. However, the most appropriate use of this disease against plant bugs may be in efforts to reduce their overwintering populations - if strains can be found that are highly effective at temperatures typical of fall and winter seasons. We conducted preliminary studies of Beauveria activity against plant bugs at temperatures of 55, 65, and 75 degrees F. Most strains of Beauveria killed a large proportion of plant bugs at all temperatures tested. Patterns of plant bug death over time varied with temperature, and our findings indicate 21 days is an appropriate duration for studies to evaluate Beauveria effectiveness under the temperatures we examined. Our results suggest that more extensive evaluations of Beauveria strains for low-temperature activity against plant bugs may be warranted.

Technical Abstract: The western tarnished plant bug, Lygus hesperus Knight, a key pest of cotton (Gossypium hirsutum L.) in production regions of the western U.S., is attacked by the naturally-occurring pathogen, Beauveria bassiana (Balsamo) Vuillemin, in the San Joaquin Valley of California. Previous research at 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 temperatures typical of fall and winter seasons. We conducted preliminary laboratory assays of Beauveria activity against Lygus at temperatures of 55, 65, and 75 degrees F. High levels of infection were obtained with most Beauveria isolates at all temperatures tested. Temporal patterns of mortality varied with temperature, and 21 days appears to be an appropriate duration for assessing mortality under the conditions we examined. Results provide a rationale for more detailed examinations of Beauveria isolates for low-temperature activity against Lygus.