Los Banos Rotary Club History
Aerial Warfare For Mosquitos

Airplane sprayed for control of mosquitos in Merced county has proven successful on the larger acreages, according to Edgar Smith, entomologist for the Merced County Mosquitos Abatement District, who, speaking at the Rotary Club luncheon in Los Banos Tuesday, told of the experimental spray work done in the county this year, and analyzed the results accomplished.

Pioneering of aerial spraying of DDT was popularized during the war by the Army and Navy, particularly in overseas areas, and at present numerous governmental agencies and many aviation companies are experimenting with new methods of spraying DDT from the air. In Merced county, an Inland Boeing 75-A, from the Inland Aviation Co., Los Banos, with pilot Tom Wilkins at the controls, has been working under contract with the Mosquito Abatement district in a 30-day spray program throughout the county, to find out just where, how and when aerial spraying will best fit into the local mosquito control problem.

During this period the district has sprayed by air approximately 8,000 acres near Merced, Planada, Los Banos, Gustine, Stevinson and Hilmar. Also they treated the Merced County Fairgrounds and the entire cities of Los Banos and Volta.

Smith said that though they are still checking final results, the experiments as a whole were decidedly successful. Most of the spraying was done in permanent pastures or swampy areas in an attempt to control both larval and adult mosquitos. Different experimental plots were sprayed with 21/2 per cent and 5 per cent DDT in oil at the rate of one gallon per acre, or a deposit of .2 to .4 pounds of DDT to the acre. The .2 pound application was sufficient to obtain kill of mosquito larvae. The higher dosage was used to insure kill of adult mosquitos and in an attempt to get enough residual effect to kill the larvae which would hatch out on the next irrigation.

The experimental work showed about 98 per cent kill on adult mosquitos and 100 per cent kill on mosquito larvae in irrigated pasture areas. Results of urban spraying were disappointing, though a noticeable decrease in the number of mosquitos was observed on the spraying of Los Banos. However, Smith said, it was not great enough and did not last long enough to warrant a large scale program of urban spraying. Further experimental work for urban areas may be made next year before a final conclusive answer can be determined.

Smith said that judging from the results of experiments so far it would seem that there is a definite place for aerial spraying in the long range problem of mosquito control in this county. This type of spraying can be used to greatest advantage in the huge pasture lands, swamps and marshes which comprise the breeding grounds of most of our mosquitos. Cost for spraying by air is about the same as ground areas for smaller plots but is cheaper when large enough areas are treated at the same time.

Smith emphasized that the greatest single factor of mosquito control is the proper drainage of agricultural and pasture lands, and this program will receive increased emphasis in the coming months. Drainage is far better on the east side of the county than it is here, Smith added, and he warned that considerable drainage work must be done here if permanent mosquito control can be accomplished in this community.
October 1, 1946

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