Humans have struggled from time immemorial to keep weeds from reducing crop yields. Now we may have some help from insects that are common in nearly every agricultural field. Pterostichus melanarius is one of the more common ground beetles in western Oregon (see picture below) that eats weed seeds such as wild proso millet and hairy nightshade. It also eats slug eggs and other insect pests as well.

Carabid ground beetles populations are often so low that they do not make a significant reduction in weed seed density in the soil. Researchers are evaluating the potential of improving habitat within crop fields to increase the number and efficiency of carabid ground beetles. Tillage is detrimental to many ground beetles, so cropping systems and tillage strategies are being developed and tested that conserve this valuable beetle resource. For instance, tillage in the spring buries many ground dwelling beetles, and may destroy eggs or larvae that will later produce adults. Eliminating some or all the tillage in the spring by strip tillage or notill planting are techniques that can be used to preserve habitat for ground beetles.

Eliminating or reducing fall tillage is another strategy that researchers are testing to improve ground beetle seed predation. Fall tillage is damaging to ground beetles because, like spring tillage, it may bury and kill beetles. Fall tillage also buries any weed seeds that have been produced during the summer. This is a one-two punch for seed predation, because there are fewer beetles to eat seeds, and the weed seeds may be buried so deep that the few ground beetles can find them.