One little grasshopper causes little damage to the garden, but when he is accompanied by lots of his friends, watch out. Raspberries (Rubus spp.), thriving in U.S. Department of Agriculture plant hardiness zones 2 through 7, are one of their favorite foods. When they find your garden, they'll return year after year, possibly in greater numbers. To keep these pesky critters from eating your fiber- and vitamin C-rich raspberries and their leaves, incorporate several management techniques for effective control.
Hand pick grasshoppers from the raspberry garden with a mild infestation. Dump them in a bucket of hot soapy water. You can also step on grasshoppers to kill them.
Maintain a 12- to 24-inch-wide border of tall, lush plants or grass, around the perimeter of the raspberry garden. Grasshoppers are likely to stay within this area of the landscape rather than entering the garden.
Sprinkle a carbaryl bait labeled to kill grasshoppers around the garden, directly on top of the soil. If you maintain a grass or plant border around the garden, apply the bait in that area, as well as other areas where grasshoppers are usually seen, such as along ditches and dense grassy areas. Perform this task in spring, preferably before you notice grasshoppers, so the young nymphs that are more susceptible eat the bait. Reapply every three or four days, and after a rain or heavy dew, until summer.
Insert tall wooden stakes around the raspberry garden, and attach metal window screening with staples to exclude grasshoppers from both the sides and top. Cover the stakes with the screen, because grasshoppers can eat through the wood.