Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2003
Publication Date: 8/15/2003
Citation: DUNKEL, F.V., JARONSKI, S. DEVELOPMENT OF A BIOASSAY SYSTEM FOR THE PREDATOR XYLOCORIS FLAVIPES (REUTER) AND ITS USE IN SUBCHRONIC TOXICITY/PATHOGENICITY STUDIES OF BEAUVERIA BASSIANA (BALS.) VUILL. STRAIN GHA. JOURNAL OF ECONOMIC ENTOMOLOGY. 2003. V. 96. Issue 4. P. 1045-1053. Interpretive Summary: Using a novel bioassay method devised for the minute pirate bug as a model heteropteran predator we determined that the insect pathogenic fungus Beauveria bassiana Strain GHA has little effect on the insect under laboratory conditions. Exposures were at doses equivalent to 10X and 100X the recommended field rate of the fungus. Grasshoppers exposed to the fungus under the same conditions were severely affected(97% mortality at 1X field rate).
Technical Abstract: Microbial biocontrol agents are useful commercially only if they do not harm other natural biocontrol organisms, at recommended use rate in the environment where the microorganism is being used. To test the hypothesis that the predatory warehouse pirate bug, Xylocoris flavipes (Reuter), is not adversely affected by the entomopathogen, Beauveria bassiana (Bals.) Vuill. strain GHA, we developed a method using individually confined bugs during a 10-day feeding regime. Three concentrations of a conidial suspension were applied to assay surfaces (filter paper disks) to achieve 2.7 x 10exp7, 2.6 x 10exp6, and 2.6 x 10exp5 conidia per cm2, representing 100 times, 10 times, and a field rate of 2.6 x 10exp13 conidia per ha (+/-10%), respectively. Fifth instar X. flavipes suffered 0% infection at the field rate when confined to treated filter paper for 10 days (16% and 42% infection, respectively, at 10 and 100 times the field rate). Second instar migratory grasshoppers, Melanoplus sanguinipes, exposed to the same doses in the same assay system suffered 97%, 92% and 100% mortality at the three respective doses 10 days after exposure. These data indicated that B. bassiana can be used safely at recommended application levels without significant effect on fifth instar populations of X. flavipes.