Submitted to: Society for Invertebrate Pathology Annual Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 5, 2001
Publication Date: August 25, 2001
Citation: JARONSKI, S. ORTHOPTERAN THERMOREGULATION AND BEHAVIORAL FEVER IN CENTRAL ALASKA-A CHILLING PROSPECT FOR ENTOMOPATHOGENS SUCH AS BEAUVERIA BASSIANA? PROCEEDINGS OF THE ANNUAL MTG OF THE SOCIETY FOR INVERTEBRATE PATHOLOGY. 2001. P. 39. Technical Abstract: The orthopterans Melanoplus borealis, M. fasciatus, M. sanguinipes, and Chorthippus curtipennis are recurring pests of forage crops in Central Alaska. Temperatures are generally cool (mean 14 C., mean high 19 C.) when grasshoppers are present (mid-June to August) with few sunny days (<10%).Under such conditions grasshoppers would be un-able to efficiently thermoregulate and raise their body temperatures to levels deleterious for entomogenous fungi.Microbial control agents such as Beauveria bassiana Strain GHA may be more efficacious than at lower latitudes. In July 2000 I examined the efficacy of B. bassiana against M. borealis, the dominant species, in outdoor shaded and unshaded enclosures, in comparison with indoor cages at a constant 21-23 C. I concurrently monitored grasshopper body temperatures. Lab-held grass- hoppers suffered 100% infection and mortality within 6 days. Outdoor,shaded dgrasshoppers had 50% mortality by day 8 and 100% not until Day 10-12. Con- trol mortality was5-10% at Day 15. Among outdoor, unshaded grasshoppers (allowed to bask when sunlight was present) mortality was delayed further delayed further, depending upon the amount of sunlight. When surviving, treated grasshoppers were moved indoors they rapidly succumbed to Beau- veria infection. Grasshoppers could raise their body temperatures to 40- 45 C. when/if the sun shone. On most days, body temperatures did not exceed 35C. or if they did, for only very short periods of time. Conversly,grass- hopper body temperatures apprached0-5C.every night.Body temps were less than 15Cfor 10 hours each day.B.bassiana GHA has a low temp. threshold of8C with growth greatly slowed below 20C.(<60%of optimun).In summary,conditions favorable for use of existing commercial mycoinsecticides in AK.