MANAGEMENT
Grasshoppers are among the most difficult insect pests to manage in the garden. When numbers are low, they can be hand-picked and squashed. Cones, screened boxes, floating row covers, and other protective covers provide some protection if numbers are not high. However, grasshoppers will eat through cloth or plastic row covers if they are hungry enough. Try using metal window screening. Poultry, including chickens and guinea hens, are excellent predators, but can also cause damage to some garden plants.
One strategy that can be used in gardens where migration of grasshoppers frequently occurs is to keep an attractive green border of tall grass or lush green plants around the perimeter of your garden to trap insects and divert them from your vegetables or flowers. Don’t mow this trap crop or let it dry out, or you will send the grasshoppers straight into your garden.
During years when huge numbers of grasshoppers are migrating, there is almost nothing you can do to protect your plants once the invasion has reached your garden. The best strategy in agricultural and rangeland areas during major migrations is to treat the grasshoppers with an insecticide early in the season when they are still young nymphs residing in uncultivated areas. Usually gardeners do not have control over these areas, however, so their management options are few. Gardeners can apply a bait containing carbaryl around the borders of their garden before grasshoppers arrive. If a grasshopper trap crop is being grown around the border of your garden, these plants can be baited or sprayed with carbaryl or other products to kill grasshoppers. These insecticides have only a few days of residual activity against grasshoppers, and baits lose their effectiveness after rain or irrigation, so they will need to be reapplied if migrations continue. Small grasshopper nymphs are easier to control with insecticides than adults and large nymphs.
Once grasshoppers have invaded the garden, insecticides will not be very effective. Reserve the use of insecticides for serious situations where they may provide a significant level of control. Carbaryl, especially in its spray form, is very toxic to bees, to natural enemies of grasshoppers, and to aquatic life.
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74103.html