5- April 1%7 E-719 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine DDT SPRAYS FOR THE CONTROL OF THE GULF COAST TICK- A PRELIMINARY REPORT By E. B. Blakeslee and W. G. Bruce Division of Insects Affecting Man and Animals Tests conducted by the Bureau of Entomology and Plant Quaran- tine in 19A5 and 1946, in cooperation with the Florida Agricultural Experiment Station, indicate that the Gulf Coast tick ( Amblyomma maculatum Koch) can be effectively controlled on cattle by the use of full-coverage DDT sprays (1). In a test at St. Augustine, Fla., in 1945, the ticks "on animals treated with a 2.5-percent DDT spray were so severely affected by the DDT residues that many of them never reached the ears of the animals. Some ticks were able to at- tach but did not survive long enough to begin engorgement, and only a negligible number lived to become completely engorged. In 19^6 an effort was made to verify the observations of the previous year and to determine the relative effectiveness of sprays and ear smears under ranch conditions. A 2.3-percent DDT spray was compared in field tests with two of the most effective ear smears known. One of these ear smears, designated as Savannah No. 5, was an experimental material containing 7.5 percent of DDT, which had been used with considerable success for the two previous years. This material resembled a slightly sticky cold cream, and repre- sented an attempt to eliminate some of the disagreeable features of viscous resins used in other smears. The other ear smear, known as stock 1037 (2), contained 5 percent of DDT in a semifluid base of nondrying resins. The 2.3-percent DDT spray was made by mixing 2 pounds of 50-percent wettable DDT powder in 5 gallons of water. Three lots of animals were treated in each test, one with each ear smear and one with the spray. A fourth lot of untreated animals was used as a check. The ear smears were applied to both the inside and outside of the animals' ears and thoroughly rubbed in with the bare hands. The spray was applied with a small power sprayer, and the animals were wet thoroughly on all parts of the body, about 1^ to 2 pints of spray being used per head. In one test, at St. Augustine, Fla., the indicated control of ticks was 68 percent for Savannah No. 5 and 82 percent for both stock 1037 and the DDT spray. In another test, at Indiantown, Fla., the indicated control was 85 percent for Savannah No. 5, 87 percent for stock 1037, and 90 percent for the DDT spray. Further evidence 1947 -2- of the effectiveness of DDT sprays against this tick was also ob- tained in a ranch test in southern Florida, where a severe tick in- festation was brought under complete control by a 2.3-percent DDT spray applied on September 4-. Suggestions for Use Although a number of questions connected with the use of DDT sprays on cattle for the control of the Gulf Coast tick have not been fully answered, the results of the tests are considered suffi- ciently definite to justify their adoption by stockmen on a trial basis. The severity of tick infestations varies so widely between different parts of the country, and sometimes between different parts of the same ranch, that is is impossible to make a blanket recommendation for all conditions. Tests show that the DDT spray is as effective as ear smears, and that it will give satisfactory control for about 1 month. It is believed that in most of the Southeast two applications of sprays during the active tick season will give satisfactory control, the first to be applied about the latter part of July or early August, and the second a month later. It should be emphasized, however, that the DDT spray is a treatment for preventing the attachment of ticks and the resulting lesions that predispose screwworm infestations. Therefore, it6 success de- pends on keeping an effective DDT residue on the animals during the active tick season. Many herds of cattle are now being treated with DDT sprays for the control of other pests, such as biting flies, mosquitoes, and lice, and their use against ear ticks will require only slight modification in the schedule of dosage and timing now in use. The minimum spray concentration required for tick control has not been determined. All the 194.6 tests were made with a 2.3-percent DDT spray, and it is suggested that for the present at least this concentration be used, especially where ticks are extremely trouble- some. The concentration should not be reduced below 1.5 percent, the strength now recommended for the control of other external para- sites of cattle in the Southeast. Whether or not the lower concen- tration will prove effective against ticks is not known. The 2.3- percent DDT spray can be made by mixing 2 pounds of wettable powder, containing 50 percent of DDT, in 5 gallons of water. Use 1 pound of the powder in 4 gallons of water to prepare a 1.5-percent spray. A few animals may be sprayed with hand equipment, but a small port- able power sprayer with a satisfactory agitator will be useful for treating larger numbers. -3- Literature Cited (1) Blakeslee, E. B., Tissot, A. N., Bruce, W. G., and Sanders, D. A. 1947. Experiments with DDT for the control of the Gulf Coast t%ck — A preliminary report. Jour. Econ. Ent. (In press.) (2) Rude, C. S. 1946. A new remedy for the control of the Culf Coast tick. U. S. Bur. Ent. and Plant Quar. E-686, 3 pp. (Processed.) UNIVERSITY OF FLORIDA 3 1262 09239 1415