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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL CONTROL OF INVASIVE PLANTS OF THE NORTHERN GREAT PLAINS

Location: Pest Management Research Unit

Title: Explaining mycoinsecticide activity: poor performance of spray and bait formulations of Beauveria bassiana and Metarhizium brunneum against Mormon cricket in field cage studies

Authors
item Foster, Nelson -
item JARONSKI, STEFAN
item Reuter, Christopher -
item Black, Lonnie -

Submitted to: Journal of Orthoptera Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 8, 2010
Publication Date: December 8, 2010
Repository URL: http://hdl.handle.net/10113/50083
Citation: Foster, N.R., Jaronski, S., Reuter, C.K., Black, L.R. 2010. Explaining mycoinsecticide activity: poor performance of spray and bait formulations of Beauveria bassiana and Metarhizium brunneum against Mormon cricket in field cage studies. Journal of Orthoptera Research. 19(2): 303-313.

Interpretive Summary: A joint ARS-APHIS PPQ field trial tested the ability of two commercial mycoinsecticides based on Beauveria bassiana GHA and Metarhizium brunneum F52 to effectively control Mormon cricket, when the fungi were applied as baits or as sprays. Both fungi were efficacious but only in insects incubated in the laboratory following two day exposure to sprayed vegetation. Bait aversion was observed when spores of either fungus were present; this was verified in the laboratory. Use of thermal surrogates of Mormon crickets, located on the ground and in the plant canopy, indicated that maximum body temperatures within field cages below 18º C, as well as above 30ºC, were common during the 14-day study. When cumulative amount of time at temperatures optimal for fungal growth (18-30º C) were calculated for the duration of the post-treatment observation period, there was an insufficient number of growth hours for mortality within the 14 day observation period. Our data illustrate the importance thermoregulation of Mormon cricket in combating fungal infection. Because thermoregulation may alter the temperatures inside the insect, several weeks may be required after treatment for infections by B. bassiana GHA and M. anisopliae F52 to cause mortality. Future studies should take this longer observational time into account.

Technical Abstract: Our objectives were threefold: (1) to evaluate B. bassiana GHA and M. anisopliae F52 for potential use against Mormon cricket (Anabrus simplex Haldeman); (2) to compare spray and bait formulations of each fungus against immature and adult Mormon cricket; and (3) to understand the effect of optimal and sub-optimal Mormon cricket body temperatures on the speed of efficacy by the two fungi. No mortality of third-instar Mormon crickets was detected in the field 14 days after treatment with fungal baits or sprays of either Beauveria bassiana Strain GHA or Metarhizium anisopliae Strain F52. Unexpected bait aversion may have adversely affected the success of the bait treatments. Lack of spray efficacy was also unexpected, given the laboratory infectivity of both fungi for Mormon cricket. Possible maximum body temperatures were estimated by thermal surrogates located on the ground and in the plant canopy within field cages. Surrogate temperatures below 18º C, as well as above 30ºC, were common during the study. When cumulative amount of time at temperatures optimal for fungal growth (18-30º C) were calculated for the duration of the post-treatment observation period, there was an insufficient number of growth hours for mortality. Our data suggest that at least 32-43 days (for M. anisopliae) or 58-75 days (for B. bassiana) should have been required for insect mortality to occur under the conditions of the test. In a second test, targeting seventh-instar nymphs and adults, the in-field mortality was not followed, but treated individuals were incubated both indoors and in outdoor cages. Infections by B. bassiana and M. anisopliae in the indoor incubated insects caused 69% and 100% mortality (corrected for untreated controls), respectively, with 71 and 80% mycosis in cadavers demonstrating the potential for field efficacy. Mormon crickets in outdoor cages succumbed to unexpected high temperatures, however. Our data illustrate the importance thermoregulation of Mormon cricket in combating fungal infection. Because physical location and thermoregulation may alter the environ inside the insect, several weeks may be required after treatment for infections by B. bassiana GHA and M. anisopliae F52 to cause mortality. Future studies should take this longer observational time into account.

Last Modified: 7/28/2014
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