When we first began working in high tunnels about 8 years ago, most of the popular literature said that the tunnels would provide protection from most insect pests, other than the usual greenhouse pests like aphids and mites. What we found very quickly is that that information was untrue. We found very high populations of a variety of insect pests within our high tunnels. Caterpillars of various types seem to be especially problematic in high tunnels. Our theory is that the moths fly into the tunnel and can’t figure out how to escape, so the females just lay their eggs on the crop they can reach. The key to managing these caterpillars is regular scouting and treating early. For the crop you are growing, look for the products recommend in the Midwest Vegetable Production Guide for caterpillars, then check Table 16 on page 45 to see if it can be used in high tunnels.