Parasitism of Parthenolecanium corni by Cordyceps fungus and various wasp parasitoids in cultivated hazelnut fields in the Midwest
Parthenolecanium corni scale insects collected from a hybrid hazelnut monoculture were reared in the lab to better understand their parasitoid fauna. Hybrid hazelnut plantings in the Upper Midwest provide a potential new crop for the region, and the study of insect communities around these plantings is relatively new. Field parasitoid rates were estimated for hymenopterous parasitoids and an entomophagous fungus, Ophiocordyceps clavulata, for two sample days in July. Additionally, the identity of reared hymenopterous parasitoids was determined. Field data was analyzed using binomial generalized linear models in R. It was discovered that Lecanium scales experienced high parasitism rates: 24.04% by hymenopteran parasitoids, and 63.39% by entomophagous fungi, giving a combined parasitism rate of 87.43%. Both types of parasitism had density-dependent relationships. Plants with higher densities of scales experienced lower parasitism rates from hymenopteran parasitoids while higher scale densities experienced higher parasitism rates from O. clavulata. A better understanding of these ecological relationships could be of benefit to hazelnut farmers if P. corni becomes a significant pest.