2007 Annual Report
Demonstration that enteric bacteria isolated from the Colorado potato beetle inhibit an otherwise promising biological control agent. The nematode Heterorhabditis marelatus and its bacterial endosymbiont Photorhabdus temperata have been shown to attack and kill Colorado potato beetle (CPB) larvae, however the full potential of these biological control agents cannot be fully realized because the nematode fails to replicate in CPB larvae. Our investigation of this system revealed that the gut bacteria associated with CPB larvae appear rapidly in the body cavities of nematode-killed larvae, and that P. temperata does not compete effectively against the gut bacteria. The failure of P. temperata to grow, and the presence of competing bacteria prevents the nematode from reproducing. This accomplishment provides an explanation for the failure of a promising biocontrol agent. The study provides an inexpensive means of screening other symbiont species and their associated nematodes for efficacy against CPB before initiating more costly field trials, by addressing the potential antagonism of CPB symbiotic bacteria to the nematode symbionts. 304 National Program Component V, Pest Control Technologies; Problem Area VD, Other Biologically-Based Control; also Problem Area IIIA – Understanding the Complex Interactions
Development of molecular non-destructive methods for use with arthropod specimens. Scientists at the Invasive Insect Biocontrol and Behavior Lab, in cooperation with the Systematic Entomology Lab, have developed a method for extracting DNA from insects and arachnids that leaves the specimen suitable for museum vouchering, so that the identity of the animal from which the DNA was removed can be verified. This should also allow the matching of previously-collected specimens with arthropods currently under study. Being able to voucher both molecular sequences and museum specimens with intact morphological characters, is also a breakthrough for systematic entomology which should have broad impact for economically important insects and overall biodiversity investigations. 304 National Program Component VI – Integrated Pest Management Systems and Areawide Suppression Problem Area VIA – Sampling Methods, Detection and Monitoring
Demonstration that spider DNA fingerprinting is reliable for their identification across geographic range. DNA sequences for a common animal molecule, Cytochrome Oxidase I, are used as barcodes, which are analogous to the DNA fingerprints used in forensic science, to identify closely related species of insects, and also to analyze interactions between insect pests and the insect predators and parasites that attack and control them. In order to determine whether these sequences are reliable across the range of each species, scientists at the Invasive Insect Biocontrol and Behavior Lab compared four species of wolf spiders and line weaving spiders from Maryland, Illinois, Mississippi, and Ohio, and found variation acceptable for use in identification throughout their range. Biological control practitioners and other scientists may therefore use them for accurate identification of these species, and to determine their role in controlling insect pests. 304 National Program Component V, Pest Control Technologies; Problem Area VD, Other Biologically-Based Control
Greenstone, M.H., Rowley, D.R., Weber, D.C. and Hawthorne, D.J. 2007. Feeding mode and prey detectability half-lives in molecular gut-content analysis: An example with two predators of the Colorado potato beetle. Bulletin of Entomological Research 97: 201-209.
Narayandas, G., Alyokhin, A., Alford, R., Weber, D.C., Dickens, J.C. 2006. "response of potato aphid (homoptera: aphididae) to natural potato odor and synthetic potato-derived colorado potato beetle kairomone". Journal of Economic Entomology. 99:1203-1208.
Blackburn, M.B., Farrar, R.R., Gundersen, D.E., Lawrence, S.D., Martin, P.A. 2007. Reproductive failure of Heterorhabditis marelatus in the Colorado potato beetle: Evidence of stress on the nematode symbiont Photorhabdus temperata, and potential interference from the enteric bacteria of the beetle. Biological Control 42:207-215.
Lawrence, S.D., Novak, N.G., Blackburn, M.B. 2007. Inhibition of proteinase inhibitor transcripts by leptinotarsa decemlineata regurgitant in lycopersicon esculentum. Journal of Chemical Ecology 33:1041-1048.