Grasshopper eggs begin to hatch in mid-June to early July. Grasshopper nymphs live for 40 to 60 days after which the adults appear and continue feeding until they are killed by cold weather. Damage caused by grasshoppers appears as irregular holes at the edge of plant leaves. As grasshoppers grow they may eat larger portions of infested leaves, and may eventually destroy every green plant in the area. Several natural controls reduce grasshopper populations in most years.
Larger grasshoppers are much more difficult to control.
Infested plants can be treated but slow control usually means damage will continue until grasshoppers already on the plants have consumed a sufficient quantity of the insecticide residue. Migration of grasshoppers from the surrounding area also limits the effectiveness of spraying just the garden plants. Insecticide sprays are more effective than dusts. Insecticides for grasshopper control include Sevin, diazinon, malathion and rotenone. Check the label to make sure the crop you intend to spray is listed on the label directions.