Control of Grasshoppers on Rangeland in the United States—A Perspective

Abstract

The periodical ravages of locusts and grasshoppers have been sufficiently documented through history that it is easy to appreciate the seriousness of such outbreaks. We believe, however, that most people grossly underestimate the forage resources that are destroyed annually by typical "noneconomical" populations of grasshoppers. The western range comprises about 262 million ha, most of which is suitable habitat for grasshoppers. The grasshoppers annually destroy at least 21-23% of available range vegetation. That would represent a loss of about $393 million/year if that vegetation could otherwise be utilized by livestock. Current control measures are not economical on about 80 million ha because treatment cost far exceeds the value of forage that is produced. Most control programs are likely to be executed on about 160 million ha that produce forage worth about $2.50 - $7.50/ha. Significant forage destruction begins during the 3rd nymphal instar. This occurs just before maturation of many important species of grass. Thus, grasshoppers do not generally inhibit forage production; rather, they hasten decomposition of the standing crop of forage. When control measures become necessary, they should be initiated as soon as possible after the majority of grasshoppers become 3rd instars. Later treatments cannot recover forage that has already been destroyed; they simply prevent further destruction.