II.4 A Review of Chemical Sprays in Cooperative Rangeland Control Programs

The chemical sprays used against rangeland grasshoppers today and the current cooperative rangeland grasshopper management program are both results of an evolving solution to an age-old problem. That problem is one of how best to control or suppress damaging populations of grasshoppers over widespread areas. The following chapter will review the history and evolution of chemical sprays in rangeland grasshopper control to the present day. History In the United States, the history of grasshopper control is interwoven with that of the Mormon cricket. Control was conducted primarily to protect crops, but rangeland also was treated to save forage and prevent insect migration to nearby cropland. During the first half of the 20th cen-tury, control relied almost exclusively on poison baits. Although sprays such as paris green and sodium arsenate were used, these compounds fell from favor because the poisoned vegetation endangered livestock (Parker 1952). Both State and Federal assistance were provided for orga-nizing and financing control efforts, particularly during outbreak years. In the late 1940’s and early 1950’s, several major devel-opments occurred that significantly changed the way grasshoppers were controlled. 1. Perhaps the most important was the development of the chlorinated hydrocarbon insecticides. They were extremely effective in small amounts against grasshop-pers. They could easily be formulated into baits, acted quickly, and had a longer residual effect than previously used baits. Because of these qualities, chlordane and toxaphene in 1949 and aldrin in 1951 quickly replaced previous baits (Parker 1952). 2. Large-scale (thousands of acres) aerial application of bait became more commonplace. Compared to older wet baits, the new compounds could be formulated dry, which made distribution easier. In Montana and Wyoming during 1949–50, aerial application of chlor-dane and toxaphene baits were the major tools used against grasshoppers (Parker 1952). 3. Sprays of these compounds were also developed at the same time. In addition to being extremely effective, they were much cheaper than baits. Sprays of chlordane, tox-aphene, and aldrin first were used in grasshopper control programs in 1947, 1948, and 1950, respectively (Parke