Although grasshoppers will feed on any kind of vegetation, they are often present without causing enough damage to warrant control measures. When control is warranted, grasshopper management can be difficult because these insects are strong fliers and can continue migrating into your yard through the entire growing season. For this reason, commercially available biological control products such as the Nosema locustae microorganisms will not help to control grasshoppers in the relatively small areas of yards and gardens. In addition, the main benefit of these microbial controls is not usually realized until the following year and usually with only partial control resulting. If these biological control products are used, the treated area should be at least 5 acres in size or larger.
Grasshoppers are most susceptible to insecticides when they are young, at the beginning of summer.
Neem, an insecticide derived from trees, is sometimes effective against some, but not all, species of grasshoppers. Neem is of very low toxicity to humans, pets, or the environment and is most effective when used in the earlier stages of the insects' life cycles, those present during and shortly after lilac bloom. Effectiveness of neem varies with the species of grasshopper. It can prevent feeding by some species, in other cases it affects insects that consume foliage that has been sprayed with the product. These products are distributed in Montana by the Wilbur-Ellis Co., the only source of which I am aware.