LEAD ARSENATE was the first residual insecticide to be used in the United States to control a soil-inhabiting insect. Since 1929 this arsenical has been applied as a topdressing to lawns and golf courses to prevent injury by the Japanese beetle, the Asiatic garden beetle, the oriental beetle, and some native white grubs. The treatment usually protects turf at least 5 years.

Lead arsenate is applied also to the soil about ornamental nursery stock to satisfy the requirements of the Federal quarantine on the Japanese beetle. Lead arsenate is a slow-acting insecticide. Since arsenicals poison the soil and impair its fertility, lead arsenate has never been popular as a general soil insecticide.

Topdressing lawns and golf courses with DDT protects them from damage by the Japanese beetle, the Asiatic garden beetle, the oriental beetle, the European chafer, and some of the native white grubs for 5 to 10 years. When DDT is mixed with the upper few inches of soil, the treatment is a basis for certifying nursery stock subject to the Federal quarantines on the Japanese beetle, the European chafer, and the white-fringed beetle. This treatment will clean up infestations of the Pacific coast wireworm in the irrigated lands of the Western States and will prevent reinfestation for at least 5 years. Most of the cutworms are controlled by disking DDT into the soil. Applying DDT in the furrow before planting apple seedlings, or in bands on the surface of the ground on either side of the planted stock, may control the woolly apple aphid.

Lindane and BHC are highly toxic to several soil-infesting insects, among which are the Japanese beetle, the European chafer, native white grubs, wireworms, the seed-corn maggot, and the southern corn rootworm. The use of these materials in the soil is limited because they spoil the flavor or impart a bad odor to such root crops as potatoes, sweetpotatoes, carrots, and beets.

Toxaphene has been used to a limited extent to control soil-infesting insects. Applied as a topdressing, it will protect lawns and golf courses from damage by the Japanese beetle, the Asiatic garden beetle, and the oriental beetle for 7 years. Late plantings of sugarcane in Louisiana are protected from injury by wireworms, centipedes, millipedes, springtails, and bristletails by applying toxaphene in the planting furrow. Toxaphene disked into the soil will control most cutworms. Placing the insecticide in bands along rows of corn is an effective control measure for cutworms in Iowa.

Chlordane kills insects faster than DDT or toxaphene but it may not remain effective so long in the soil. A single topdressing of chlordane will protect lawns and golf courses for 5 years from damage by the Japanese beetle, the Asiatic garden beetle, the oriental beetle, and the European chafer, and for 2 years against the imported fire ant. Crops are protected from damage by the imported and native white grubs, wireworms, and cutworms by mixing chlordane with the upper few inches of soil. Good control of the clover root curculio on alfalfa is obtained by applying chlordane before seeding the crop or late in the fall. An application of chlordane will control the cabbage maggot, the onion maggot, and the southern corn rootworm. Applying chlordane in the planting furrow is effective in controlling wire-worms, centipedes, millipedes, spring-tails, and bristletails in fields of sugarcane, and gives promise of controlling the woolly apple aphid on the roots of young apple trees.

The insecticides developed more recently--aldrin, dieldrin, and heptachlor are more toxic to insects than chlordane, and only very small amounts are needed to control many soil-infesting insects, among which are the Japanese beetle, the European chafer, the Asiatic garden beetle, the oriental beetle, the white-fringed beetle, native white grubs, wireworms, the false wireworm, the onion maggot, the cabbage maggot, the seed-corn maggot, the sugar-beet root maggot, the plum curculio, the clover root curculio, the sweetpotato weevil, the southern corn rootworm, the northern corn rootworm, the mole cricket, the imported fire ant, the corn root aphid, cutworms, and the grape colaspis.

The direct application of the new chlorinated organic residual insecticides to soil is advantageous in that as much as needed can be applied to control the noxious insects present or anticipated.

The promiscuous use of these materials is to be avoided, however, because excessive amounts may impair the fertility of the soil and damage the crop.

The insecticide may be broadcast in cultivated fields and worked into the soil, placed in the planting furrow, or applied as sidedressings to row crops, using it in the form of a dust, or granulated formulation, alone or in combination with a commercial fertilizer, or as a dilute emulsion. The row treatments give protection to the crop but are not so effective as the broadcast treatments in the overall reduction of the insect population. The various formulations, pound for pound of insecticide, appear equally effective in the soil, when properly prepared and used.

The treatment of seed with a residual insecticide before planting is relatively new. A wide variety of seeds, including corn, cotton, small grains, beans, beets, onions, cucumbers, tomatoes, lettuce, and peas, have been treated with dusts and slurries of the new chlorinated organic insecticides. These treatments are of value in protecting the seed from injury by such insects as the seed-corn maggot, the seed-corn beetle, false wireworms, and wireworms, but they probably afford little protection to the roots of established seedlings.

Although most crops seem to endure the insecticidal treatments and do not take up readily from the soil at least some of the chlorinated organic insecticides, the Food and Drug Administration has not established tolerances for many crops grown in soil treated with these materials. Until these tolerances are established, the only safe policy for the grower is to assume that no residue is permitted on or in the crop at harvest.

Under the circumstances, farmers should follow carefully the recommendations of their county agricultural agent and their State agricultural experiment station in the use of the chlorinated organic insecticides for the control of noxious insects in the soil.

Farmers can depend also on the recommendations on the labels of the formulations in interstate commerce because these are approved by the Department of Agriculture.