Range and Pasture XIX-1

Introduction to Insects

John B. Campbell

The most important economic insect groups that affect pasture and rangeland in the Northern Great Plains are grasshoppers, Western harvester ants and white grubs. Occasionally damage can occur from the big-eyed or black grass bugs (Labops) and Mormon crickets. Because of the diversity of plant species found in grassland areas, there is also a great diversity of insects inhabiting range and pasture. Leafhoppers, stem boring insects, wireworms, cutworms, weevils, spittle bugs, stink bugs, plant bugs and numerous other plant feeding insects are sometimes numerous enough that they are probably causing economic injury. But little is known about the economic injury level for most of the insects so no effort is made to control them. Losses from these insects would have to be quite high to warrant treatment on low value grassland.

The federal government, through the Animal and Plant Health Inspection Service (APHIS) has in the past provided money for rangeland grasshopper control. In addition, many of the states also helped in defraying costs for grasshoppers control. The usual cost-share program was one-half by APHIS, one-fourth by the state and one-fourth by the rancher-owner. This program was established in the drought years of the 1930's by Congress with the concept that it would help both ranchers and farmers, although only rangeland was treated. But in 1996, the federal program was abolished and most states had already stopped providing funds for grasshopper control. Consequently, it is now up to the individual ranchers to treat for grasshoppers at their own expense. Since it is generally too expensive to treat the whole pasture or all of the rangeland on a ranch, we recommend treating only the more valuable grass production areas.

Grasshoppers tend to be more numerous during drought years, but they also tend to cycle, gradually increasing in numbers over a period of several years. Generally, an infestation will cover rather large regions often encompassing thousands of acres. Under these circumstances, we would suggest ranchers cooperate, much as they did in the APHIS control programs, by mapping the acres they want treated, and requesting bids from aerial applicators for treatment. County extension educators could help them with this process. The U.S. Department of Agriculture Agricultural Research Service (ARS) and APHIS have developed a computer model for range grasshoppers, which when supplied with current data on range conditions, climatic data, cattle prices, grasshopper species and numbers will provide an economic, cost-benefit analysis that can be used in treatment decisions. This computer software grasshopper model is readily available at no cost for extension educators.

Categories: Range, Pasture, Introduction, Insects

Date: 06/11/2002