Biology and Phenology of the Hop-vine Borer, Hydraecia immanis Guenée, and Detection of the Potato Stem Borer, H. micacea (Esper) (Lepidoptera: Noctuidae), in Wisconsin

Abstract

We describe the phenology and developmental biology of the hop-vine borer ( Hydraecia immanis ) over a 4-year period (1979–1982) in relation to the major change in feeding habits and food availability. The first two to four instars feed on grass stems then move to adjacent corn plants to complete their feeding. In view of this feeding habit it seems likely that increasing trends toward reduced-tillage and conservation-tillage practices in the Midwest can only contribute to spread of H. immanis in the future. In contrast, its introduced European relative (the polyphagous potato stem borer, H. micacea Esper) has a similar biology but a wider range of host plants, including potatoes, corn, and many other plants as well as hops. This relative was introduced to North America approximately 80 years ago hut has only recently spread across Canada from New York State. We now report that it has been detected in Wisconsin where it is currently separated in noticeable economic damage from the hop-vine borer by only a single county. The implications of hybridization or continued geographic spread of these two species for Midwest agriculture may be significant and are briefly discussed.