I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
There is not a really good way to control grasshoppers since they are migratory.
You could try applying an insecticide to the leaves to kill the insects. However, treating the plants with pesticide may kill grasshoppers that eat leaves, but more will simply migrate in thus rendering that option not so effective in preventing damage. There is a natural spore that is quite effective against nymphs. It is known as Nolo Bait. However there is still the problem of the insects migrating in from an untreated area.
Another option is to cover the plants with a lightweight, spunbound polyester rowcover fabric or some type of fine netting. This can help protect the plants from the grasshoppers. However, during an especially bad invasion last year I spoke with a friend who stated that grasshoppers had eaten their way through the rowcover!
Some gardeners have reported that sprays of kaolin clay (available at some local garden centers and online) will repel grasshoppers. These sprays leave the plant foliage white but don't harm the plant. They wash off the foliage with rains and thus are not permanent.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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