Several fumigating methods, such as treatment with dilute emulsions containing carbon disulfide, methyl bromide, or ethylene dibromide, are effective, but have to be applied annually. Other materials have been developed that remain effective for a number of years.

Lead arsenate at the rate of 435 pounds an acre has been used for grub-proofing turf since 1929. Among the various arsenicals tested, it is the least detrimental to grasses. Such grub-proofing is effective for 5 years or more. Lead arsenate, however, has several objectionable features. It is a slow-acting poison. Its effectiveness and lasting qualities vary greatly in different soils because of its reaction with the different soil constituents. It reduces the effectiveness of certain fertilizers. Finally, it sometimes makes difficult the establishment of newly seeded grass.

DDT and chlordane are effective and practical. Like lead arsenate, they kill the grubs while they are feeding on roots or burrowing in the soil. They kill the newly hatched grubs faster than the older and larger ones. They work best at high temperatures and have little or no effect at temperatures below 50 F., when the grubs are practically inactive. DDT and chlordane are not affected by the common fertilizers and soil conditioners. Neither seems to interfere with the actions of fertilizers on plants. The common grasses are tolerant to both materials.

DDT applied at the rate of 25 pounds an acre to established turf kills grubs about two times faster than lead arsenate at the rate of 435 pounds an acre. Equally good results are obtained with DDT applied as a dust or as a spray. Either a wettable powder or an emulsion can be used in preparing the spray. When DDT is applied late in the fall or in the spring, it can be expected that about one-third of the fully grown grubs in the soil will be killed before changing to beetles in June. Both treatments, however, will practically eliminate by mid-September all grubs of the next annual brood that hatch during the summer. The number of years that one application of DDT will be effective in grub-proofing turf has not been determined. The oldest experimental treatment, applied in the spring of 1944, has eliminated eight annual broods. More recent applications at various localities in New Jersey, Connecticut, Massachusetts, and North Carolina have shown no sign of reduced effectiveness.

DDT has largely replaced lead arsenate for grub-proofing because it kills grubs faster, is less influenced by soil conditions, remains effective just as long, and is less likely to injure grasses. In 1952 it was cheaper than lead arsenate.

Chlordane at the rate of 1 pounds an acre kills grubs twice as fast as DDT at the rate of 25 pounds an acre. A treatment applied in September, while the fully grown grubs are active, will kill more than - go percent of them within 3 weeks. When the treatment is applied in late fall or early spring while the grubs are inactive, however, few grubs will be killed until late in the spring. The period during which one application of chlordane will be effective has not been determined. The oldest experimental treatments, applied in the spring of 1947 in New Jersey, Connecticut, and Massachusetts, have eliminated five annual broods. Since chlordane kills grubs faster than DDT, it is more effective in reducing populations of grubs in the spring and fall. When a dense infestation is discovered during those seasons, damage to turf can be stopped faster by an application of chlordane than by using DDT. Both materials are now used extensively for grub-proofing.

Of numerous other organic compounds that have been tested as grub-proofing materials since 1946, the best results have been obtained with aldrin and dieldrin. Either, at the rate of 3 pounds an acre, kills grubs 1.5 times as fast as 10 pounds of chlordane and 4 times as fast as 25 pounds of DDT. The common grasses are tolerant to them. The tests have not been under way long enough to determine whether the effects of aldrin or dieldrin last long enough to justify recommending them for grub-proofing.

ISOLATED INFESTATIONS Of the beetle in localities remote from the generally infested area can be controlled and the normal rapid increase in the population greatly retarded by treating the soil with DDT at the rate of 25 pounds an acre. This has been demonstrated with such an infestation in North Carolina, where about 250 acres were treated in 1945. The number of beetles was reduced to a low level and it has not increased very much since that time. In contrast, the infestation in a nearby untreated area increased rapidly and spread over the countryside. Either DDT or chlordane may be used for the treatment of isolated infestations.

CHEMICAL TREATMENTS for fruits and vegetables have been developed to permit their shipment to areas where the beetle does not occur. The shipper may choose the treatment that is best suited to his needs and is least likely to cause damage to the commodity. Carbon disulfide, vaporized at the rate of 10 pounds to each 1,000 cubic feet in a closed chamber, was the first method developed for killing adult beetles in packages of blueberries, blackberries, raspberries, and strawberries. Because of the explosion hazard, this material has been replaced by ethylene oxide or methyl bromide, which are not explosive at the strengths employed and are equally effective for the fumigation of fruits and vegetables. A DDT treatment has now superseded the fumigating procedures for potatoes and sacked onions because it is cheaper and more easily applied under commercial conditions. Refrigerator cars are treated by blowing 1 ounce of 10 percent DDT dust per 2,500 cubic feet into the loaded cars. Trucks with tightly enclosed bodies are treated by applying 1 ounce of the dust before and after loading.

Methods have been developed for the treatment of soil about the roots of plants so that the nurseries and greenhouses within the infested area may continue to conduct business in other parts of the country. All of the immature stages of the beetle in soil, compost, and decomposed manure used for potting plants are destroyed by fumigating with carbon disulfide or methyl bromide in a closed chamber, by mixing flakes of naphthalene throughout the material, or by heating the mass to 130 F. and maintaining it at this temperature for 30 minutes. During the seasons when only the grubs are present, the soil may be fumigated with chloropicrin or with a mixture of ethylene dibromide and ethylene dichloride. With these treatments, screening is necessary when beetles are around, to prevent reinfestation. Mixing DDT, chlordane, or lead arsenate with the potting medium will destroy the infestation present at the time of application and will destroy any infestation which may be introduced during the following 2 years.