Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2005
Publication Date: 7/1/2004
Citation: Leland, J.E., Snodgrass, G.L. 2004. Prevalence of naturally occurring beauveria bassiana in lygus lineolaris populations on wild host plants in the delta and hill country regions of mississippi. Journal of Agricultural and Urban Entomology. Interpretive Summary: A fungus (Beauveria bassiana) is being evaluated for control of an important insect pest of cotton, tarnished plant bug. Isolates of this fungus obtained from tarnished plant bugs in cotton growing regions may be better suited for controlling these populations. Surveys were conducted in Mississippi to determine the prevalence of this fungus in tarnished plant bugs populations from wild host plants. Nine wild host plants were sampled over a three year period. Percentage of tarnished plant bugs infected with this fungus ranged from 0 to 8% and averaged 0.3%. This level of infection was much lower than that previously observed in western tarnished plant bugs from California, which averaged approximately 10%. Nonetheless, 23 new isolates of this fungus were obtained from this survey, which will be evaluated for characteristics to select one for development as a control agent of tarnished plant bugs. This survey also provides information on background natural infection levels in tarnished plant bug populations from wild host plants of Mississippi, which will be useful in evaluating the impact of field trials with this fungus against these populations. Tarnished plant bug populations from wild host plants were evaluated for there susceptibility to a the same species of fungus used in a commercial product and resulting mortality was not influenced by the insects' host plant or time of year that they were collected.
Technical Abstract: Surveys of natural Beauveria bassiana (Balsamo) infection levels in tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), populations from wild host plants in Mississippi were conducted. Populations of L. lineolaris were sampled from nine dominant wild host plants over a three year period by sweep net and held for sporulation as evidence of infection with B. bassiana. Percentage infection from L. lineolaris populations on wild host plants ranged from 0 to 8% and averaged 0.3%. Incidence of L. lineolaris infection was not correlated with Julian date but was inversely correlated with L. lineolaris population density. The highest incidence of natural infection was found in populations from goldenrod, Solidago altissima (L.) and natural infection among populations from all other wild host plants were similar. Despite the low incidence of natural infection, 23 new isolates of B. bassiana from L. lineolaris were discovered which will be evaluated for characteristics relevant to developing a microbial biocontrol strategy for L. lineolaris. Additionally, susceptibility of L. lineolaris to B. bassiana (GHA) was compared among different populations from wild host plants in laboratory bioassays. Pathogenicity of B. bassiana (GHA) to L. lineolaris adults was similar among populations from different host plants and collection dates. Natural infection levels will be useful when evaluating the efficacy of B. bassiana in field trials targeting these populations and evaluating potential for displacement of naturally-occurring B. bassiana isolates.