Grasshoppers have little chance of surviving the new sprays, which kill both by contact and as internal poisons. Even if they escape being hit by the spray the first meal of treated vegetation will be their last. Kills with the best sprays usually reach go percent in 3 days and continue for 1 or 2 weeks. Populations of 25 to 100 per square yard have been reduced to less than 1 grasshopper in 10 square yards. Such kills give complete protection to crops and range. If spraying is done early enough to prevent egg laying no further control will be needed for several years unless grasshoppers move in from untreated land.

Sprays have other advantages over baits. Standard acre dosages applied as sprays have controlled infestations regardless of the number of grasshoppers per square yard. Bait application must be varied according to numbers present, which can be determined only by time-consuming surveys of the area to be treated. Use of too much bait is wasteful and expensive; too little is still more expensive if re-treatment becomes necessary. Spray materials are more stable in price than bran and cost less to transport and store. Bran for bait is in direct competition with bran for livestock and frequently soars to high prices when large quantities are needed for grasshopper control. Loading planes with sprays takes less time than with bait. A plane loaded with spray can cover more acres than the same plane loaded with bait. The overall cost of spraying is less than baiting.

Of the various new insecticides tested against grasshoppers as sprays, chlorinated hydrocarbons have given the best results and are lowest in cost on a per-acre basis. Chlordane spray was first used in grasshopper control programs in 1947, toxaphene in 1948, and aldrin in 1950. Acre dosages are: Toxaphene, 1 to 1 1/2 pounds; chlordane, 1/2 to 1 pound; and aldrin, 1 to 2 ounces.

Almost complete destruction of grasshoppers by spraying half a gallon of kerosene containing 2 ounces of poison over an acre seems almost incredible but that is what aldrin does.

Before new insecticides are recommended for general use in grasshopper control they are subjected to extensive tests. Preliminary screening is done in winter with laboratory-reared grasshoppers. The first step is to administer carefully measured quantities of the new insecticide to individual grasshoppers and compare the results with those of a standard chemical for which effective individual and acre dosages have been established. Materials that show slight killing action are discarded. Those that show promise are used in laboratory dusting and spraying experiments. Contact action is tested by treating the grasshoppers and holding them on untreated green plants; stomach action is determined by placing untreated grasshoppers on sprayed or dusted plants. Baits are tested by exposing measured quantities to grasshoppers in screen cages. Laboratory results sometimes agree closely with those obtained later in the field but not always. How the insecticide performs outdoors is most important but laboratory tests are of great value as indicators of the most promising dosage levels for initial field trials.

Field tests, using ground equipment, are made on small plots (1.5 to 5 acres) under a wide variety of conditions. Insecticides outstanding in small plot tests are next applied by ground equipment and airplanes on 10 to 40-acre plots, and finally on large tracts.

When the Bureau of Entomology and Plant Quarantine is convinced that an insecticide it has tested is worth recommending for general use, its findings are reported to the State Leaders' Advisory Committee on Grasshopper Control at its annual meeting in Denver, Colo. Data available from State and commercial organizations are also considered. If agreement is reached on formulations and acre dosages, the insecticide is recommended for general use the following year.

Thereafter the insecticide is given farm-scale testing. That is done to compare it with insecticides previously recommended and to test it under the special conditions in the various representative agricultural districts. Blocks of grasshopper-infested farms growing the typical crops of the district are used. The intensity of infestation is determined by surveys of eggs and young grasshoppers in the spring before control is started and by surveys of eggs and adults in the fall after control is completed. Control measures are applied to all economic infestations within the block, regardless of their location. Records are kept of quantities of insecticides used, cost of application, kills obtained, and crop damage. The areas are rechecked to find out if control one year prevents damage the following year.

Such tests have been conducted in corn and small grains in South Dakota, in seed alfalfa in South Dakota and Nebraska, and in flax and small grains in North Dakota. Results proved that crop protection is attainable at reasonable cost by correctly timed applications of new insecticides: One year's effort in treating all economic infestations within a block of farms will eliminate or greatly reduce the need for grasshopper control for several years thereafter. Farmers have shown keen interest in these tests, have commented favorably on them, and have been quick to adopt the control measures.

J. R. PARKER is in charge of research on grasshoppers and Mormon crickets It the Bozeman, Mont., field station of the Bureau of Entomology and Plant Quarantine. Dr. Parker represented the United States at the International Conference on Locusts and Their Control in Cairo, Egypt, in 1936, and was a consulting delegate to the Second Inter-American Conference on Agriculture at Mexico City in 1942. In 1952 he received the Department's Distinguished Service Award for his work on grasshopper and locust control.