Detection of Gonatocerus ashmeadi (Hymenoptera: Mymaridae) parasitism of Homalodisca coagulata (Homoptera: Cicadellidae) eggs by polyacrylamide gel electrophoresis of esterases

Gonatocerus ashmeadi is an important egg parasitoid of the glassy-winged sharpshooter, Homalodisca coagulata, in California. Although adults of this parasitoid are easily identified from morphological characteristics, their identification as immatures within eggs is more difficult, particularly during the early stages of development. In this study, we show that esterase profiles determined by polyacrylamide gel electrophoresis (PAGE) can be used to detect this species in parasitized eggs within two days of parasitization. The expression of esterase E0.17 occurred at a time when mymarid parasitoids would be expected to hatch within the host egg. The intensity of this band increased as the parasitoid developed within the sharpshooter egg. After five days, a second parasitoid esterase, E0.13, was detected. These two esterases were clearly distinct from all sharpshooter esterases. The electrophoretic technique was also sensitive enough to detect a polymorphic esterase locus in adult insects originating from San Juan Capistrano in California.