2012 Annual Report
1a.Objectives (from AD-416):
To devise innovative methods for the suppression of insects that transmit diseases to U.S. military deployed abroad.
1b.Approach (from AD-416):
Identify and test compounds with insecticidal activity that makes them especially
beneficial in the rapid control o fmosquitoes, flies, and other arthropods responsible for carrying disease agent. Devise innovative means of applying control agents especially suited for use in combat or deployment conditions. Identify and test new classes of topical and area repellents for use by troops.
Previously, our research efforts directed at arthropod repelling folk remedies identified saturated fatty acids and mono-unsaturated fatty acids with carbon chain lengths of C10, 11, and 12 as those responsible for the activities. This was documented with structure-activity relationship studies in a paper that is in press. These lead repellent candidates were evaluated in a repellency evaluation involving humans, where significant repellency was demonstrated comparable to DEET. Again, fatty acids with carbon chain lengths of C10 to 12 were the most active. A spatial mosquito repellent delivery device in the form of a candle has also been developed to test the activity of these lead fatty acid candidates. Preliminary field spatial repellency evaluations were performed by an ARS scientist. Data indicated significant repellency above solvent control but additional replications and treatments are needed and will be performed next year. Modifications of the delivery device may also be made. Explorations for a cheaper source of these bioactive insect repelling fatty acids is currently underway utilizing various oilseed crops and associated knowledge in collaboration with ARS colleagues in Peoria, Illinois. We have already evaluated at least three oilseed extracts containing the desired fatty acid profiles that may be used in delivery devices. Additional repellency evaluations of these oils will be completed this year and the same oils will also be incorporated into the delivery devices. Preliminary evaluations of two Acorus species were completed for mosquito deterrent activity. Acorus (A.) calamus and A. tatarinowii were active against mosquito larvae. A. calamus had adult mosquito repellent activity. Angelica dahurica derivatives were found to have mosquito biting deterrent activity. We are currently acquiring several different and unique species of Acorus and Angelica. Syn 131-1, a highly active mosquito repellent was synthesized in bulk quantities for toxicology tests. Inhalation tests will be done later after the skin, eye, and dermal irritation tests. Syn 131-1 is also being tested against sand flies. An industrial waste from the food industry was found to be very active as a mosquito larvacide. On 1st instar Aedis (Ae.) aegypti larvae, some of the fractions were highly active at 15 parts per million (ppm). Pure compounds from these fractions have been isolated and identified, some analogs have been synthesized and are being tested further. These compounds are resorcinol analogs with varying alkyl side chains and degree of unsaturation. Monomethyl and dimethyl analogs have been synthesized for testing. A collaborative project on native plant species (Asteraceae, Apiaceae and Lilliaceae) growing in Alaska has been initiated. A tick repellent compound was isolated from the seeds of Ligusticum scorticum seeds and some fractions from Cinidium cinidiifolium seed extract and are being tested further. In a laboratory assay, the active compound is more active than DEET. We have received the whole plants of Chrysanthemum (C.) cinidiifolium, and the extracts have been sent to the Center for Medical, Agricultural and Veterinary Entomology (CMAVE) to evaluate activity against mosquitoes.