Gypsy moth entering trap.

During the early years of the work hydraulic sprayers were used to spray infested places with lead arsenate. Now Federal workers use the more effective and economical aircraft and blower equipment, but hydraulic equipment is still used in small commercial spraying operations. One Government-owned C-47 equipped for dispensing DDT solution can spray in an hour an area that formerly would take nine hydraulic units a whole season. Federal costs of operating hydraulic equipment averaged 25 dollars an acre. DDT-oil solution can be applied by airplane or mist blower for less than a dollar an acre. The gypsy moth is eradicated entirely when the solution is applied properly. Small single-engine biplanes of the N3N-3 type and multiple-engine types such as the C-47 have been adapted for the spraying.

The small biplanes are equipped with 90 and 110 gallon insecticide tanks located in the forward cockpit. The insecticide is pumped under pressure from the tank to the dispensing nozzle by a small gear-type pump hung beneath the fuselage just aft of the landing wheels. The pump is powered by a propeller connected with it which is mounted in suitable ball bearings and equipped with a braking mechanism. Forward motion of the plane turns the propeller at approximately 2,500 revolutions per minute, which in turn actuates the pump. The flow of insecticide is controlled by solenoid valves suitably located and operated electrically from a switch in the pilot's cockpit. The airplanes fly approximately 50 feet above the tree tops at about 80 miles an hour, pumping out insecticide solution at the rate of 20 gallons a minute and laying down a swath 100 to 110 feet wide.

The C-47 carries two cylindrical oil-resistant rubber-lined aluminum tanks with a capacity of 922 gallons of insecticide. A centrifugal-type pump and gasoline unit mounted aft of the tanks forces the insecticide solution out through aluminum piping and hose connections to streamlined booms mounted beneath the wings and fuselage. Electric motor-operated valves control the flow of insecticide to the booms. Nozzles with small check valves are spaced along the booms to deliver the proper amount of insecticide material. This plane flies 150 miles, an hour at 150 to 200 feet above the trees. The output of insecticide is 150 gallons a minute. The effective swath width is about 600 feet. The dosage is applied at the standard rate of 1 gallon of solution per acre. In a normal operating season, 15,000 acres can be treated by a small biplane and 80,000 acres by a C-47.

In order to supply the aircraft with insecticide in large-scale spraying operations, large storage and mixing facilities are needed. Mixing tanks are equipped with heating units so that the insecticide can be heated to 80 F. to facilitate dissolving the technical grade DDT powder in the oil.

Ground mist blowers are effective for roadside spraying of woodlands. They are also used for spraying locations such as junk yards to prevent artificial spread of the insect. Blower units are mounted on trucks suitable for traveling along back roads and trails. The speed of the truck and the output of the blower are regulated so that the DDT-oil solution is applied at the rate of a gallon an acre.

Large-scale spraying operations require a great deal of planning. Maps are prepared showing areas to be treated. Just before the spraying season, windsocks are erected at specified locations for the guidance of aircraft. Property owners, as well as city, town, and other officials, including water commissioners, fish and game authorities, and the police are interviewed. Before and during the operations, radio stations and newspapers inform the citizens about the purpose and progress of the program.

Before the start of aerial spraying each day, small glass plates are placed on the ground in a line at right angles to the line of flight in order to check on the distribution of spray deposit. Plates not adequately covered give indication of areas that must be resprayed.

Six-foot-long helium-inflated dirigible-shaped balloons have proved effective as a guide for the large multi-engine airplanes, as they are visible for 2 to 5 miles.

In New Jersey and Pennsylvania, funds and manpower were furnished to supplement Federal efforts. Since 1935, surveys in New Jersey have been conducted by the State. In Pennsylvania trapping has been cooperative, with the Federal Government providing technical supervision. In New York State, in addition to supervision of the work programs, the New York Conservation Department has provided the manpower and most of the insecticides and solvents used in extensive spraying operations.

Cooperation among the Conservation Department of the Commonwealth of Massachusetts, the counties of Barnstable and Plymouth, and municipalities therein, assisted by the Federal Government, made it possible to spray the two counties completely in 1949 and 1950.

The principal long-time objective is the eventual eradication of the gypsy moth from the United States.

CURRENT OBJECTIVES are: To conduct trapping and scouting surveys in Pennsylvania until extermination there is assured; eliminate general infestation in New York by 1953 with only mop-up of isolated incipient infestations remaining in succeeding years; reduce the intensity of infestation in western New England and minimize the hazard of westward spread of the pest; continue the large-scale coordinated cooperative eradication program in southeastern Massachusetts; and to furnish technical advice and limited assistance to States, counties, cities, and towns engaged in control in the New England States.

JOHN M. CORLISS has been connected with plant-disease and insect-control projects since he joined the Department of Agriculture in 1917. In the program to prevent the spread of the white pine blister rust disease in 1928, he was in charge of transit inspection at Chicago. He was assigned to the division of gypsy moth control in 1943 and was in charge of the control measures against that insect in New Jersey, New York, and Pennsylvania until 1947, when he was made chief of the division of gypsy and brown-tail moth control.