|Vander Meer, Robert - Bob|
Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2011
Publication Date: 7/1/2011
Publication URL: http://handle.nal.usda.gov/10113/55830
Citation: Sharma, K., Vander Meer, R.K., Fadamiro, H. 2011. Phorid fly, Pseudacteon tricuspis, response to alkylpyrazine analogs of a fire ant, Solenopsis invicta, alarm pheromone. Journal of Insect Physiology. 57:939-944. Interpretive Summary: The red imported fire ant, S. invicta, is among the world’s 100 worst invasive alien species. In the United States this ant species infests more than 320 million acres in 13 southern tier states and Puerto Rico and are spreading northward. It is estimated to be responsible for almost $7 billion annually in damage repair, medical care, and control costs. In the last decade S. invicta has changed from an invasive pest ant in the United States to a global problem, with infestations occurring in Australia, Taiwan, mainland China, Mexico and many Caribbean Island countries. Biological control agents, such as phorid fly-parasitoids, will play an important role in controlling populations. Therefore, understanding how the flies interact with their host is very important. Scientists from the Imported Fire Ant and Household Insect Unit at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, FL and from Auburn University have investigated how the flies find their host fire ants. The results confirm that the reported fire ant alarm pheromone component plays a role in mediating attraction of phorid flies to host workers. Venom alkaloids were previously shown to attract P. tricuspis; therefore, it is proposed that fire ant alarm pheromones may act in tandem or synergistically with venom alkaloids to attract phorid fly parasitoids to fire ant workers. This work can be used to increase phorid fly detection sensitivity and rearing efficiency for subsequent release.
Technical Abstract: The phorid fly, Pseudacteon tricuspis Borgmeier, is a parasitoid of the red imported fire ant, Solenopsis invicta Buren. This fly has been reported to use fire ant chemicals, specifically venom alkaloids and possibly alarm pheromone to locate its host. A recent study identified 2-ethyl-3,6-dimethyl pyrazine as a component of the alarm pheromone of S. invicta. To determine the possible involvement of this fire ant alarm pheromone component in mediating fire ant-phorid fly interactions, we tested electroantennogram (EAG) and behavioral responses of P. tricuspis females to the commercially available mixture of 2-ethyl-3,6-dimethyl pyrazine and its 3,5 dimethyl isomer, as well as six structurally related alkylpyrazine analogs at varying doses. Pseudacteon tricuspis females showed significant EAG response to 2-ethyl-3,6(or 5)-dimethyl pyrazine at all doses, 0.001 to 10 'g. One of the six alkylpyrazine analogs, 2,3-diethyl-5-methyl pyrazine also showed significant EAG activity at 0.1 and 1 'g. Results of four-choice olfactometer bioassays demonstrated significant attraction of P. tricuspis females to 2-ethyl-3,6(or 5)-dimethyl pyrazine (1) at all tested doses (0.01, 0.1, 1 and 10 'g). The analogues, 2,3-diethyl-5-methyl pyrazine (2) and 2,3-dimethyl pyrazine (3) were significantly better than the control at the higher doses (0.1, 1 and 10 'g). The synthetic alarm pheromone (1) was significantly better than the two pyrazine analogs (compounds 2 and 3) at two doses, 0.1 and 1 'g. These results confirm that the reported fire ant alarm pheromone component plays a role in mediating attraction of phorid flies to host workers. Venom alkaloids were previously shown to attract P. tricuspis; therefore, we propose that fire ant alarm pheromones may act in tandem or synergistically with venom alkaloids to attract phorid fly parasitoids to fire ant workers.