Role of the egg parasitoid Trichogramma minutum in biological control of the grape berry moth, Endopiza viteana

During a survey for natural enemies of thegrape berry moth (GBM) Endopiza viteana(Clemens) in northwestern Pennsylvania, wefound that Trichogramma minutum Riley isthe only native egg parasitoid with thepotential to limit berry damage by preventingegg hatch. Natural parasitism, however, wasfound to be unreliable for providing economicpest suppression. Early season populations ofthe parasitoid are extremely low and may be theresult of inadequate alternative host eggs foroverwintering. Also, wild grapes and theirwooded habitats were found to be favored byT. minutum. Parasitism was low incultivated grapes and in wild grapes growingclose to commercial vineyards (possibly due tothe deterrent effect of insecticides) andhighest in sites 1.5 km from commercialvineyards. Adult T. minutum emergingfrom GBM eggs were exceptionally small andshowed little vigor. Parasitized eggs oftenfailed to produce adult parasitoids. Pre-adults in such eggs had poorly formed mouth-parts or lacked them altogether. Inundativereleases of laboratory-reared T. minutumin border rows of vineyards are suggested as apossible alternative to the current practice ofapplying carbamate and organophosphateinsecticides, which are inimical to beneficialarthropods.