From 0 to 5,000 in 34 Years

Kenneth Messenger, W. L. Popham.

The airplane has become such a useful tool in the fight against insects that in 1952 more than 5,000 of them were equipped for that purpose in the United States.

Attempts were made as early as 1918 to control insects in this country by dumping poison dust from airplanes while flying over crops. But by 1921 a specially equipped airplane demonstrated its effectiveness in controlling an infestation of the catalpa sphinx near Dayton, Ohio. The lead arsenate dust that was released from a Curtiss biplane under the supervision of C. R. Neillie and J. S. Houser was unusually effective.

The following year B. R. Coad, of the Bureau of Entomology and Plant Quarantine, borrowed two airplanes of the same type from the United States Air Service and applied dust to fields of cotton near Tallulah, La., for the control of the boll weevil, which then was destroying 250 million dollars worth of cotton annually. Dr. Coad reported that "the speed of operation was at least 100 times as fast as the best mule-drawn machine."

Those demonstrations led to the commercial use of aircraft for insect control. The following year Huff-Daland Dusters, Inc., began commercial aircraft dusting in the Southern States. An industry was born.

During the two decades that followed, many experiments were made with different types of aircraft, different installations, and different materials, but few major improvements are recorded. Devices for wetting dusts as they were released, to make them adhere better to foliage, were tried in the New England forests with only moderate success. Autogiros and a blimp were tested in the belief that their slower forward speed might improve forest coverage. But it was not until the early part of the Second World War that the airplane's real potential as a pest-control vehicle became obvious. At that time the exposure of troops to insect-borne diseases challenged the initiative of entomologists, chemists, and military leaders. The answer to that challenge broad sheets of DDT spray streaming from fast transport aircraft, blanketing otherwise inaccessible insect-breeding areas saved countless lives and countless dollars.

As early as 1911 a German forest warden applied for a patent covering the use of aircraft in combating forest pests. His effort apparently aroused no great interest in Germany until 1925 when several investigations, similar to those previously carried on in the United States, were undertaken. In that year a stand of mixed timber was treated to suppress an outbreak of the nun moth. Officials called the results excellent, with no apparent harmful effects on birds or game."

Airplane dusting to control locusts was tried about the same time by the Russians. In 1925, near Haguenau, France, a forest plantation was dusted by aircraft. In 1927, on Cape Breton Island, Nova Scotia, the airplane was used to dust spruce and balsam in an attempt to control a spruce budworm outbreak.

Mosquito-breeding areas in South Africa, the United States, and other parts of the world were treated before 1930 with paris green. So encouraging were the results that it was forecast that the day would come when the airplane could be used to eradicate from entire continents the tsetse fly, carrier of sleeping sickness, and the malaria-carrying mosquitoes.

At the Orlando, Fla., laboratory of the Bureau of Entomology and Plant Quarantine, E. F. Knipling and two of his associates, C. N. Husman and O. M. Longcoy, demonstrated that DDT in a concentrated solution applied from aircraft at the rate of 1 gallon or less per acre gave good control of both mosquitoes and flies. Husman developed several devices for military trainer biplanes that made it possible to appraise accurately the effectiveness of this method of pest control. He continued this work during an assignment by the Navy in the South Pacific and developed improved equipment quite similar to that in use today. David G. Hall, also an employee of the Bureau, further developed and supervised methods of spraying mosquito-infested areas while in the service of the Army Transport Command in the South Pacific. In this work, he equipped and directed C-47 transports with great effectiveness.

Another type of equipment installed in aircraft for mosquito control was tested extensively by the Tennessee Valley Authority during 1945 and 1946. This consisted of an exhaust generator which produced DDT aerosols. It gave a rather uniform coverage over wide swaths at exceedingly low rates of discharge. The installation was simple and inexpensive, but its use was limited to specific problems. Although it effectively penetrated heavy vegetation, the drop size of the spray was so small that it had very little residual value.

Although the cost of aircraft applications was fairly high in the postwar period, it has been progressively reduced as a result of continued research in the development of concentrated materials and application equipment. The improvements and the growing realization of the versatility and effectiveness of the airplane resulted in a marked increase in the number used each year since the war.

Despite shortcomings the difficulty of controlling the distribution of an insecticide from the air, the drift of fine sprays into nearby areas, the sometimes higher costs nearly 500,000 hours are flown by pest-control aircraft annually.

Illustrative of the importance of the airplane in suppressing large emergency outbreaks of insect pests are the following projects, conducted cooperatively by the Bureau of Entomology and Plant Quarantine, the Forest Service, States, and other organizations.

During the few years before 1952, hundreds of thousands of acres were sprayed by aircraft for the control of the gypsy moth in New England. In this work it is estimated that just one load of insecticide released by a C-47 airplane treats as large an area as could be covered by one truck-borne spray rig in 4 years and more effectively.

Also during recent years, several million acres in the Northwest have been sprayed with aircraft for the control of the spruce budworm. In 1948 an outbreak of the tussock moth in the Northwest infested 450,000 acres. Within a period of a few weeks the entire area was sprayed so effectively that the treatment did not have to be repeated. Each year between 1949 and 1952, several hundred thousand acres were treated with baits and sprays to control grasshoppers on forage lands of Wyoming and Montana.

KENNETH MESSENGER, a graduate of the University of California, has worked on agricultural pest-control programs since 1933. He is in charge of the Aircraft and Special Equipment Center at Oklahoma City of the Bureau of Entomology and Plant Quarantine.

W. L. POPHAM has taken part in large-scale plant disease and insect control programs since his graduation from Montana State College in 1924. He has been assistant chief of the Bureau of Entomology and Plant Quarantine since 1941. He received the degree of doctor of science from Montana State College in 1948.

More information about the use of aircraft for applying insecticides will be found in the following chapter and in many of the chapters in the second half of this book, which give details about types of aircraft and spray formulations used to control specific insects.