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14

In the field experiment, technical difficulties necessitated rather high application rates, and all chemicals were applied at the rate of four pounds active ingredient per acre.

Field experiment using granular insecticides

During the course of the summer, it soon became obvious that a large concentration of evenly distributed earwigs would be difficult to find; but luckily one heavy infestation occurred in an irrigated truck garden in Young Ward, Utah and became especially serious on garden vegetables, namely, potatoes, tomatoes and celery, toward the latter part of July. This site was chosen for a field experiment, using granular forms of aldrin, chlordane, dieldrin and heptachlor.

Each of the four chemicals was applied as granules to four 200 square-foot plots at the rate of four pounds per acre. Chlordane, dieldrin and heptachlor were applied with a small rotary hand duster calibrated to a fixed walking pace. Aldrin had to be applied by hand in order to effect a four-pound per acre treatment. These treatments were made on August 3rd in the afternoon between the hours of two and four; and traps were put out (five per plot) between four and six of the same afternoon. The granules had little opportunity to contact earwigs before six o'clock, as they are not active and exposed during the daylight hours.

The traps were removed the following morning and taken to the laboratory for a nymphal and adult count. They were replaced in the field in the afternoons of August 5th, 12th and 28th, with counts being made each succeeding morning.

Four control plots were scattered throughout the area, well away from any of the treated plots. Counts from these controls constituted