INSECTICIDES AND REPELLENTS 73 



TICKS 



Ticks are vectors of Rocky Mountain spotted fever, Bullis fever, 

 numerous other rickettsial diseases, tularemia, and Q fever, as well 

 as pests of man and domestic animals in many areas. Tick control 

 is usually aimed at the prevention of their development on animal 

 hosts and often requires long campaigns. For the immediate pro- 

 tection of troops in the field the use of clothing impregnated with a 

 repellent is the most feasible method now available (see pp. 75-80). 

 Area control of both ticks and chiggers in and around campsites is 

 sometimes desirable. 



The commonest species of wood ticks in the Eastern United States 

 are the American dog tick and the lone star tick. DDT, chlordane, 

 dieldrin, and toxaphene have given satisfactory control of these 

 species and presumably would be effective against others. Dosages of 

 1 to 2 pounds per acre in solutions or emulsions or 2 to 3 pounds in 

 10-percent dusts are recommended. Thorough application should 

 be made to the litter on the ground and to low vegetation. Parathion 

 gave good control of the lone star tick at ){ to }i pound per acre, but 

 because of its high toxicity to humans it is not recommended for 

 general use. 



Only the adults of the American dog tick attack man, and they 

 usually congregate on vegetation along the edges of roads and trails. 

 A high degree of control has been accomplished by treating a strip 

 20 to 30 feet wide on each side of the road or trail. The larvae and 

 nymphs as well as adults of the lone star tick will attach themselves 

 to persons, and the three stages are found principally in brushy thickets 

 that are commonly used by deer. Application of insecticides in 

 some localities may be limited to such thickets. For either species a 

 preliminary survey should be made to determine the location of the 

 heaviest infestations. A white flannel cloth dragged over the grass 

 and ground duff will show these places. 



Ticks infesting living quarters and other buildings are usually 

 brown dog ticks. They can be killed with DDT or chlordane. A 

 spray containing 5 percent of DDT or 2 percent of chlordane should 

 be applied to cracks, crevices, and behind objects where the ticks hide. 

 A combination spray and dust treatment may be advantageous if the 

 hiding places cannot be readily reached by the spray. 



Both the American and the brown dog ticks are brought onto the 

 premises by dogs. These ticks can be controlled with a wash contain- 

 ing 1 percent of DDT or 0.01 percent of lindane. A DDT wettable 

 powder or a lindane emulsifiable concentrate should be used to prepare 

 the wash. A 10-percent DDT dust may also be used, but it is less 

 thorough and effective. Derris or cube washes or powders have long 

 been in use for tick control on dogs. A suitable wash may be made 

 by mixing 2 ounces of fine derris or cube powder and 1 ounce of 

 neutral soap in 1 gallon of tepid water. The powder should contain 

 at least 3 percent of rotenone. 



CHIGGERS 



The larvae of trombiculid mites, commonly called chiggers or red- 

 bugs, are important pests of troops in some parts of the United States 



