Hop Vine Borer

Hydraecia immanis

Hop vine borers can be a major pest of hops and corn under the right conditions. Early instar larvae prefer grasses, but later instars switch to corn or hops and can easily kill plants. Originally found in eastern Iowa, they have since expanded geographically.
Hop vine borers have distinct markings, with square dark brown or purple spots separated by white lines. Their head is orange or brown in color.
Hop vine borers bore hollow at the portion of the stem beneath the ground. This kills small plants (up to V8 in corn), and severaly damages larger plants. The reduced stand and damaged plants can result in significant yield losses.
Soil-applied insecticides have not proven effective against hop vine borer. However, insecticides applied within the first week of emergence may provide some level of protection. Insecticides applied later cannot reach the larvae and are not effective. Always read and follow all label instructions.
Adult moths lay eggs on grasses, and young larvae prefer grasses. Long term control is best achieved by removing grasses from the field and surrounding areas.