Lygus bugs have piercing-sucking mouthparts and physically damage the plants by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. In alfalfa, these bugs cause short stem internodes, excessive branching and small, distorted leaves. Feeding on the buds and blossoms cause these to drop. Feeding on the seeds in the pods causes the seeds to shrivel and turn brown.
Similar damage is seen in canola crops.
Adult plant bugs may invade the fields during the early bud stage. The nymphs may appear at the flowering stage. Nymphs and adults may feed on the buds, flowers and seeds of canola plants. Puncture marks in the pods are visible and sometimes a small drop of plant juice exudes from the wound. Often, damage in canola fields is not noticed until swathing.