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Title: Volatiles from waste larval rearing media attract gravid screwworm flies (Diptera: Calliphoridae) to oviposit

Author
item Chaudhury, Muhammad
item Zhu, Junwei - Jerry
item SAGEL, AGUSTIN - Us Embassy, Panama
item Chen, Hong
item Skoda, Steven

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2014
Publication Date: 5/1/2014
Publication URL: http://handle.nal.usda.gov/10113/58728
Citation: Chaudhury, M.F., Zhu, J.J., Sagel, A., Chen, H., Skoda, S.R. 2014. Volatiles from waste larval rearing media attract gravid screwworm flies (Diptera: Calliphoridae) to oviposit. Journal of Medical Entomology. 51(3):591-595.

Interpretive Summary: Primary screwworms were once an important pest of livestock and humans in the U.S. The successful eradication of primary screwworms from North America was achieved using the sterile insect technique. Now a barrier at the Panama to Columbia border protects North America from reinfections by this insidious pest. Maintaining the barrier requires surveillance, accomplished by trapping, as well as the release of sterilized screwworms from a mass rearing facility. Techniques to improve mass rearing and trapping will benefit the barrier maintenance program. Female screwworm flies are attracted to gases emanating from waste media used for rearing immature screwworms to deposit their eggs. The gases were analyzed and five chemical compounds were identified, which were attractive to female screwworm flies of egg-laying age. A synthetic blend of these chemicals was prepared and tested for effectiveness in attracting female screwworm flies to deposit their eggs. Secondary screwworm flies were used as a model in landing experiments and significantly more egg-laying females were attracted to the substrate treated with the chemical blend compared to those attracted to substrate treated only with ethanol. In egg-laying experiments, primary screwworm flies laid significantly more eggs on substrates treated with waste media, 10- and 100-fold diluted blend compared to substrates of the undiluted blend and ethanol. Secondary screwworm flies laid significantly fewer eggs than did the primary screwworm females. These results indicate that the synthetic blend of the five compounds identified from the gas of waste media may serve as an attractant for oviposition for primary screwworm as well as for the secondary screwworm flies.

Technical Abstract: Gravid screwworm flies, Cochliomyia hominivorax, are attracted to the volatiles from waste larval rearing media to deposit eggs. Studies were conducted to identify chemicals from the waste media volatiles and determine their effectiveness to attract gravid flies to oviposit. Volatiles were collected using solid phase microextraction (SPME) method, and five active chemicals were identified using gas chromatography-mass spectrometry (GC-MS). In electroantennography (EAG) studies, antennae of gravid screwworm flies, Cochliomyia macellaria, responded positively to the identified compounds, - dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol, and indole. A synthetic blend of these five compounds was prepared and tested using laboratory bioassay methods for their effectiveness to attract gravid flies to oviposit. Tests were conducted with both C. hominivorax and C. macellaria. Significantly more gravid C. macellaria were attracted and landed on substrates treated with 10-fold diluted blends compared to those landed on substrates treated with ethanol only (as control). Only a few young females and young and old males were attracted to the substrates treated with the synthetic blend. In the oviposition experiments, C. hominivorax females laid significantly more eggs on substrates treated with waste media, 10- and 100-fold diluted blend compared to substrates with undiluted blend and ethanol. Cochliomyia macellaria females deposited significantly fewer eggs than did C. hominivorax females. These results indicate that the synthetic blend of five compounds identified may serve as an oviposition attractant for C. hominivorax as well as for C. macellaria.