Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/8/2005
Publication Date: 9/1/2006
Citation: Mcguire, M.R., Leland, J.E., Dara, S., Park, Y.H., Ulloa, M. 2006. Effect of different isolates of Beauveria bassiana on field populations of Lygus hesperus. Biol. Cont. 38:390-396. Interpretive Summary: Lygus bugs cause damage to a number of economically important crops including cotton and broad spectrum chemical pesticides are typically applied for their control. Concerns over loss of natural enemy populations and potential for insecticide resistance development by Lygus has spurred efforts to develop a control that is specific and effective. A fungus, called Beauveria bassiana infects and kills Lygus and we previously reported than several isolates of the fungus from California and Mississippi were effective in the laboratory. In this manuscript, we report the effectiveness of the new isolates in the field for controlling Lygus. Following application of fungus to alfalfa fields infested with Lygus, approximately 80% of the insects were infected. Natural enemies were not affected. Lygus populations declined 10-14 days after application suggesting a delayed impact. In addition, we report a new molecular technique to determine which fungus isolate infected Lygus. These results should be of interest to other scientists looking for new ways to control Lygus on a variety of crops, as well as companies producing Beauveria for commercial use.
Technical Abstract: Lygus hesperus (Knight) is a particularly damaging pest of many crops in the Western United States. Current control tactics are chemically based and there is some concern over resistance building up in populations. Based on previous laboratory studies conducted in California and Mississippi, USA, two new isolates of the entomopathogenic fungus Beauveria bassiana were selected for field-testing against L. hesperus in CA. Alfalfa plots were treated with one of three isolates of B. bassiana (the commercial isolate, an isolate from CA (WTPB2) or an isolate from MS (TPB3)) or the chemical pesticide Warrior T. Adults collected from plots 3d after application with B. bassiana were heavily infected but no differences in percentage infection occurred among fungal treatments. In addition, approximately 30% of the insects collected from control plots or plots treated with Warrior were also infected. PCR analysis using SSR markers revealed that the isolate causing most of the infections in fungus treated plots was the isolate applied. A mix of infections was found in control plots and plots treated with Warrior T. Despite high levels of infection, no significant reductions of adult populations occurred until 10 – 14 days after application when plots treated with Warrior or B. bassiana had about half the numbers of adult L. hesperus as the control plots.