The harvester ants clear all vegetation from the ground around their nests, and use the seeds for food. The leaf-cutting ants also denude the ground around their nests but carry the foliage to their nests to serve as the medium on which to grow a mold which they use for food.

When properly and persistently applied, various insecticides have been used effectively against all three species for many years, although complete eradication of colonies is very difficult. More recently dieldrin, chlordane, and methyl bromide have been added to the list of chemicals found useful against them. One of the most effective and easily applied insecticides is a dust containing 2 percent of dieldrin. For a medium- or large-sized colony spread about one-half pound of the dust thinly in a continuous band 4 to 6 inches wide to form a circle 5 to 6 feet in diameter around the entrance tunnel of the nest. For small colonies with a cleared area less than 6 feet wide, place the band of dust around the edge of the cleared area and reduce the dosage proportionately. In irrigated areas apply the dust as soon as possible after the surface of the flooded land has dried.

In the larger colonies new entrances may be opened outside the dust ring. Treat these entrances individually or include them in the same ring with the original entrance when making the next application. Inspect all treated colonies every 2 or 3 weeks, and re-treat those showing activity, until all are inactive. Inspections can then be made less frequently.

Apply the dust on warm days when there is little wind, and renew the band if it becomes broken or washed away. In handling dieldrin special care must be taken to observe the safety precautions given on page 271 or on containers.

A 5 percent chlordane dust applied in the manner just described for dieldrin dust will give fairly good control. It does not remain effective as long as dieldrin and more applications usually are necessary to subdue the ant colonies. A 10 percent chlordane dust sifted thinly over the cleared areas surrounding colony entrances has given good results in trials conducted in the Rio Grande Valley by the Texas Agricultural Experiment Station.

Methyl bromide has also given good control of ant colonies in moist soil. This fumigant is a liquid sold in cans which forms a heavy poisonous vapor when released, and must not be inhaled. It is injected into the nest openings with a mechanical dispenser that can be attached to the can. Apply 2 fluid ounces of the fumigant per colony and pack the soil tight over the entrance hole to prevent the gas from escaping. Methyl bromide is also sold in small glass ampules that can be inserted and broken in harvester ant nests with a special applicator.

THE SUGARCANE BORER damages sugarcane, corn, and sorghum in the Gulf States in much the same way as the European corn borer injures corn in the Northern States. The yellowish white, brown-spotted larva is about 1 inch long when full-grown and turns into a small straw-colored moth. Although it is able to survive only in tropical and semitropical regions, it is one of the worst insect enemies of sugarcane, corn, and sorghum along the Gulf coast and in Florida, where it produces several generations a year.

For about 10 years a full-strength cryolite dust has been widely and profitably used against the sugarcane borer in Louisiana. Four applications are made at weekly intervals while the first- or spring-generation borers are hatching from eggs laid on the cane leaves by the moths. The dust is applied with airplanes or ground equipment at the rate of 10 pounds per acre, very early in the morning while the air is still and the plants are wet with dew. Where it is used to control the second or midsummer generation the same number of weekly applications are made by airplane, the stand of cane by that time being too tall and thick for the use of ground equipment. For several reasons first-generation dusting is preferable.

After several years of testing, a dust containing 40 percent of ryania was recommended in 1950 for use against the sugarcane borer. It is applied at the same dosage and in the same way as cryolite.

AMONG THE ENEMIES that attack sugarcane underground are wireworms and several small soil-inhabiting insects and related animals. The losses they cause can be much reduced by deep drainage of the soil, by the planting of varieties that give thick stands of cane and recover well from injury, and by planting the cane in late summer rather than in the fall in order to promote rapid vigorous growth and the production of good stands of cane before cold weather. Because of the difficulty of completing the planting of large acreages before fall, the application of these cultural control measures is not always practicable. Investigations have shown that stands can be increased equally well by applying a 1 percent chlordane or toxaphene dust at the rate of 400 pounds per acre on the seed cane as it is placed in the furrows at planting time, and then covering it with soil in the usual way. This method of control would enable the grower to plant his cane in the fall with confidence that insects and related pests will not prevent the development of a good stand.

PROGRESS is being made by entomologists and chemists in the Department of Agriculture, State experiment stations, and industry toward practical control measures for a number of other insect pests of cereal and forage crops, that have not been mentioned.

A few figures will show the importance of the investigations to the production of staple food and feed crops. A billion dollars a year is a conservative estimate of the annual losses caused by the insect pests of these crops during production and storage. The annual losses caused by only a few of the insects, including the corn earworm, European corn borer, chinch bug, hessian fly, and grasshoppers, during the growth of the crops they attack, total some 300 million dollars. That is less than 3 percent of the farm value of the crops. The additional losses caused by the insect pests of grains and cereal products while in farm and commercial storage are estimated to be in the neighborhood of 600 million dollars a year. A billion dollars worth of staple foods saved from destruction of insects would feed a lot of ill-nourished or starving people.

C. M. PACKARD is an entomologist.

He was in the division of cereal and forage insect investigations, Bureau of Entomology and Plant Quarantine, for 37 years and retired on September 30, 1950. Until 1937, when he was put in charge of that division with headquarters in Washington, he worked from various field stations on the biology and control of cereal and forage insects.

Spotted cucumber beetle.