Mitigating Philornis parasitism on the Ridgway's Hawk: mid- and long-term control methods.

QUIROGA, M.; HAYES, C.; CORDERO-RODRIGUEZ; ANDERSON, D.; HAYES, T.

La Fortuna

Conferencia; IV Neotropical Raptor Conference; 2016

The Peregrine Fund

Philornis (Diptera: Muscidae), is a genus of Neotropical dipterans thatparasitize birds. Knowledge on the genus is limited to 28 of the approximately50 described species and their effect on hosts vary from light to lethal; sometimestaking bird species to the border of extinction (i.e., parasitism of MangroveFinch by P. downsi). This is also thecase of the critically endangered Ridgway´s Hawk (Buteo ridgwayi) whose nestlings are negatively affected by theparasitism of Philornis (mainly P. pici). Although some control methods are being developed toeradicate P. downsi from the GalápagosIslands where it was introduced in the 1970?s,we need to develop control methods for Hispaniola where evidence suggests that Philornis pici is native. We arecurrently studying mid- and long-term control methods (MTM and LTM respectively).MTM we have tested include repellents that may keep flies away from nests, along lasting insecticide (23% permethrin - Permacap®) to reduce the number oftimes that nests are treated, and a bait-insecticide (Spinosad). Advancestowards LTM have been made by seeking biological control agents and attemptingto reproduce P. pici?s life cycle in captivity, keyinformation that will allow the implementation of known techniques like SterileMale Release Technique. Resultsshowed that annatto (Bixa orellana),DEET, and Picaridin could potentially be good repellents of P. pici since a majority of flies (>78%) exposed to thesesubstances either moved away from the repellent or stayed at the base of the choicearena. Permacap controlled larvae and adults for up to 25 days when sprayed onnest material, which may allow us to prevent Philornis infestations with fewer treatments. Spinosad also showedinteresting results: 100% of the flies fed with 10% spinosad died within 61hours whereas control flies were still alive. Regarding LTM, of 150 flies thatpupated, we were able to maintain a majority (69%) alive for at least 24 daysand observed that P. pici malesshowed significantly longer wings as well as longer and wider bodies thanfemales. Furthermore, we observed that P.pici was parasitized by Brachymeriapodagrica, a parasitic wasp. Although more research is needed, our findingsprovide information on methods with potential to control P. pici parasitism in the mid- and long-term.