PACIFIC CIFIC COAST WIREWORM

Showing damage to carrot, potato, and onion-, a. larva (natural size) on potato. A, eggs; B. larva; C, pupa in underground cell; D. adult click beetle. (A. B, C. and D, bout three times natural size.)

PACIFIC COAST WIREWORM

The Pacific Coast wireworm is one of the most destructive of the many kinds of wireworms in the United States. It is generally distributed in the irrigated lands west of the Rocky Mountains. The shiny, tough, yellow-to-orange insects feed only on the underground parts of plants. They have a long life cycle-2 to 5 years in the soil. They injure crops by destroying seeds, cutting off small underground stems, and boring holes in the larger stems, roots, and tubers. No vegetable or field crop is immune to the damage they do. Such crops as potatoes, onions, corn, lettuce, beans, sugar beets, tomatoes, peas, carrots, and melons are particularly susceptible to their attacks.

The Pacific Coast wireworm hatches from tiny white eggs laid in the soil by the parent click beetles early in the spring. The beetles die soon after. The small wireworms grow to about one-fourth inch in length by fall. Most of them become full-grown, about three-fourths inch long, in 3 years. They change to pupae during midsummer. The pupae change to adults in about 3 weeks, but the adults remain in the soil within earthen cells until spring, when they emerge to lay eggs.

Control: To control wireworms in irrigated lands, treat the soil with 10 pounds of DDT per acre after harvest in the summer or fall or before planting in the spring. Spray or dust the insecticide on the soil surface and thoroughly mix it into the soil 6 to 9 inches deep. The Pacific Coast wireworm is killed by this insecticide in 6 to 8 weeks after application, but the material will remain in the soil and prevent new infestations for several years.