Silk fly electroantennography, a crucial step for semiochemical investigations

Silk flies (Euxesta and Chaetopsis spp.,Diptera: Ulidiidae) are severe pests of sweet corn in Florida, Central, and South America.  Identification of attractive semiochemicals may facilitate development of improved monitoring and management strategies for these pests.   To this end, an electroantennography (EAG) method was devised to identify raw materials that elicit strong olfactory responses from which volatiles can be collected and identified.  Whole silk fly heads were mounted on micropipette electrodes filled with 0.1 M KCL solution using a salt free electrode gel.  Antennal responses to corn tassel, corn silk, and armyworm frass collected from tassel-fed worms (tassel frass) and from silk-fed worms (silk frass) were recorded using a Syntech EAG system.  Dose response curves to headspace frass volatiles were constructed for mature and immature Euxesta eluta females.  Immature E. eluta females were more sensitive to frass volatiles than mature females.  Of the substrates evaluated, corn silk elicited the lowest antennal responses and silk frass elicited the strongest responses among the three species tested.  Therefore, silk frass volatiles are being investigated further.  This is the first time that electroantennography has been reported for species of silk fly.