A fumigant consisting of a mixture of ethylene oxide and carbon dioxide is useful against the cigarette beetle and the tobacco moth under vacuum conditions, particularly in the case of manufactured cigars and cigar tobaccos. This fumigant has the advantage of not leaving any objectionable odor but it is not effective at temperatures below approximately 60 F.

Tobacco flea beetle.

Methyl bromide is a satisfactory fumigant in closed tobacco storages, but under some circumstances obnoxious odors develop. Methyl bromide is more dangerous to handle than the other commonly used tobacco fumigants.

A chemical consisting of equal parts of acrylonitrile and carbon tetrachloride is an effective fumigant for insects affecting stored tobacco in closed storages. It has not been widely adopted because of the possible fire hazard involved, but it promises to become an effective substitute for hydrogen cyanide gas.

Aerosols containing DDT, pyrethrum or lindane have given a moderate degree of success, and research on this method of insecticide application is being continued.

The problem of protecting tobacco in open storage has been studied. In that type of storage, the fumigation methods used in closed storages obviously are impracticable. Several years ago a method was devised for the treatment of the interior of open-storage warehouses by applying pyrethrum dust with special equipment directed against the adults of the cigarette beetle and the tobacco moth. The treatment proved helpful, but the dust deposits that accumulated as the result of repeated applications were objectionable. Recently a finely divided pyrethrum-oil spray has been found more effective than pyrethrum dust against the adults of insects affecting tobacco in open-storage warehouses. Special equipment had to be developed to apply the spray to the interior of the warehouses, and the successful accomplishment of this project has led to the widespread adoption of spraying as a standard procedure in the control of insects in open warehouses.

Until recent years most of the research on the control of insects in stored tobacco dealt with the cigarette type of tobacco, since this type is held in storage for aging longer than the other types. Beginning in 1948, however, emphasis was shifted to the cigar type of tobacco, for which cyanide fumigation is objectionable in some respects, and to the adaptation of fumigation and spraying procedures to factory conditions. Greater emphasis also has been placed on studying methods for protecting cigarettes, cigars, and other manufactured products from insect damage.

The problem of devising materials for covers or liners of containers for stored tobacco, or manufactured products, that would exclude or repel insects has been given some attention. Various types of paper and plastic substances have been tested to line hogsheads prior to packing the tobacco therein. Similarly, many different coverings, including paper impregnated with a pyrethrum-piperonyl butoxide combination have been tested as coverings for cigarettes and cigars. None of these materials has been completely successful.

In many areas the tobacco moth periodically infests harvested tobacco in packhouses on the farms. Many of the infestations were originally caused by adults of the tobacco moth which bred in and escaped from nearby open-storage warehouses. The screening of these open-storage units so that the moths cannot escape and gain entrance to tobacco packhouses has aided greatly in solving this problem, as has the elimination of, or screening of, grains or feedstuffs stored nearby, which also function as breeding sources. Pack-house sanitation, including the disposition of scrap tobacco and similar trash, also aids greatly in reducing the local population of the tobacco moth, and minimizes the likelihood of infestation of the harvested tobacco stored in the packhouse. The application of pyrethrum dust to the interior of infested tobacco packhouses was found to be effective in killing the adults.

Special studies on the effect of cold storage or cool storage disclosed that this common commercial practice is of value in preventing or checking an insect infestation in stored or manufactured tobacco. Conversely, many factory processes, particularly in the instance of domestic cigarette types of tobacco, involve a re-drying operation of the stored tobacco. The machines used in this operation subject the tobacco to high temperatures. A study of this treatment revealed that all insect infestation is killed in the presence of the high temperatures used in the operation. The re-dried tobacco is subject to reinfestation, however, when held in an infested factory or storage warehouse and may later require fumigation.

D. J. CAFFREY joined the Bureau of Entomology and Plant Quarantine in 1913. He is well known for his research in the field of cereal and forage insect investigations, particularly on the European corn borer, range caterpillar, clover seed chalcid, alfalfa caterpillar, and wheat straw-worm. He initiated many of the fundamental studies leading to the development of control measures for the European corn borer.

Since entering the division of truck crop and garden insect investigations in 1931 as assistant division leader, he has been closely identified with the research on tobacco insects.