Grasshoppers are worse in hot dry years. When we have cool, wet springs, they can succumb to disease that keeps their numbers in check. Some years they don’t show up until the end of May and June. In 2006, they arrived in March, and even as late as August, young ones still appeared.
Control is difficult unless since it’s hard to hit them with a contact spray. The best thing to do, as soon as you see the nymphs, is to apply a bait. If you see leaves with tiny holes, or find more than 8 grasshoppers to a square yard, it’s time to treat.
Effective baits include Nolo Bait or Semaspore. Both contain a protozoa called Nosema locustae which is impregnated in bran flakes sweetened with sugar.
Apply by hand or with a rotary spreader, early in the morning, when grasshoppers are feeding. They don’t just drop dead – they’ll slow down and cling to plants. You won’t see any dead ones, since the healthy grasshoppers cannibalize the sick and weakened ones. Those grasshoppers will then ingest the protozoa; females will pass it along through their eggs. You’ll see a better reduction in population if you are diligent and enlist your neighbors in the project as well.
Be sure to use fresh bait that has kept chilled at the store, and bring it home in an ice chest. Grasshoppers will not be attracted to old bait. Look at the formulation date on the side of the container. If not chilled, it will last for 4 weeks. If refrigerated, a container will last 4 months.
You can also use a spray of Kaolin clay, available at craft stores that sell pottery supplies. Mix it up in a pump-up sprayer – 2 ½ cups of clay to a gallon water plus a teaspoon of soap as a surfactant. It’s important that you constantly agitate the sprayer while you work! Spray leaves lightly. It leaves a fine film of powder on the leaves, which gums up a grasshopper’s mouthparts, so it won’t eat there. The film also acts as sort of a shade cloth to protect leaves in summer’s heat! Obviously this won’t work if you use a sprinkler system, and must be reapplied after a rain.
Another prevention against grasshoppers is tightly staked row cover for plants that do not require pollination.