Enhancing the Efficacy of Beauveria bassiana for Mole Cricket (Orthoptera: Gryllotalpidae) Control in Turfgrass
THOMPSON, SARAH RACHEL. Enhancing the Efficacy of Beauveria bassiana for Mole Cricket (Orthoptera: Gryllotalpidae) Control in Turfgrass. (Under the direction of Rick L. Brandenburg.)
The objectives of this research conducted with the entomogenous fungus, Beauveria bassiana, include: a) to measure the effect of UV exposure and applied irrigation on the viability of conidia b) to determine the type of interaction that exists between various strains of the fungus and other insecticides and c) to elucidate the mechanism that mole crickets use to detect and avoid contact with the conidia. Field studies to evaluate the impact of UV light and moisture on conidial viability were conducted in July-August 2004 and August-September 2005. In a baseline viability study, both strains were able to persist in the environment up to 21 days after application. There were significant differences for both strains at two different levels of irrigation, with plots receiving 15.3 cm of irrigation during the study maintaining spore viability better than plots receiving 7.5 cm of irrigation. Oil formulations containing an optical brightener or magnesium silicate clay increased conidial viability by approximately 10% compared to the oil or clay alone formulations. Laboratory topical bioassays were conducted to determine the interaction between B. bassiana and diatomaceous earth (DE) or imidacloprid. For all three strains tested, there was significantly more mortality in combination treatments involving the fungus and DE compared to either treatment alone at a sublethal dose. These interactions were synergistic for two strains. The percentage mortalities caused by combination treatments involving sublethal doses of imidacloprid and B. bassiana were less than additive for all strains. This interaction was antagonistic for one strain. Behavioral studies with tawny and southern mole crickets were conducted to determine the mechanism that mole crickets use to detect and avoid contact with B. bassiana conidia. Significant variations in behavior suggest a chemosensory mechanism of detection. Avoidance behaviors were more extreme for southern mole crickets, suggesting a more sensitive response. Results from these studies emphasize the impact of abiotic factors on the use of B. bassiana for mole cricket control and suggest methods to increase efficacy.
Advisor:Wes Watson; Jim Arends; Wayne Brooks; Rick L. Brandenburg
School:North Carolina State University
School Location:USA - North Carolina
Source Type:Master's Thesis
Date of Publication:04/12/2006