INSECTICIDES AND REPELLENTS 57 



and suitably spaced to give thorough coverage of the room or building. 

 The nozzles were operated at pressures of 2 to 5 p. s. i. through an air 

 line connected with a compressor. In messhalls a small electric 

 pump was used, and in dairies the necessary air pressure was obtained 

 through the milking-machine pump by adjusting a valve in the cylin- 

 der head, which caused a changeover from vacuum to pressure in the 

 air lines. These units were low in cost and simple to operate. 



The fixed aerosol units consisted of solenoid-controlled dispensers, 

 each with four outlets pointing in different directions, connected by 

 }4-inch copper tubing with a reservoir tank and an electric timer. 

 Each unit delivered 0.8 gram of aerosol per second, and several units 

 were suitably spaced on the ceiling to give the desired dosage. More 

 mechanical difficulties, due chiefly to leakage and stoppage of the 

 nozzles, were experienced with the aerosol than with the fixed-spray 

 equipment. It was also more expensive to install and operate. 



Most of the tests with these two types of equipment were carried 

 out in open dairy barns, and the results were variable, chiefly because 

 flies escaped as soon as the spraying was started. However, it is 

 believed that such units would be highly effective in buildings that 

 can be closed sufficiently to prevent escape of flies before they receive 

 a lethal dose of the insecticide. For such locations the fixed spray 

 would be preferred over the aerosol equipment. 



Aerial spraying is seldom employed for the control of flies, but may be 

 resorted to where they are abundant over a wide area and immediate 

 control is desired. Such conditions may occur in combat areas as a 

 result of unsanitary conditions and fly breeding in dead bodies. The 

 dosages of different insecticides required for effective control by this 

 method are not known, but for preliminary tests to determine the 

 proper dosage the use of two to four times the amount used against 

 mosquitoes is suggested. DDT, chlordane, lindane, and possibly 

 dieldrin are insecticides of choice for mixed populations of house 

 flies, blow flies, and others. 



POISONED BAITS 



For house fly control in areas where a high resistance to the residual 

 sprays has developed, the use of poisoned baits has been very effective. 

 Formerly a 1 -percent solution of formaldehyde (2.5 to 3 percent of 

 40-percent formalin) or sodium salicylate in sweetened water or milk 

 was employed to reduce fly infestations in the house. At this low 

 concentration neither material is regarded as poisonous to humans or 

 pets. During World War II a 1 -percent solution of sodium arsenite 

 in diluted molasses was found to make an effective poisoned fly bait 

 when sprayed arouud fecal deposits, garbage, and dead bodies. 



In more recent work at Orlando a 2-percent solution of sodium 

 arsenate in equal parts of water and either blackstrap molasses or 

 malt gave about 90 percent control of house flies in heavily infested 

 dairy barns. Pans containing 2 liters of solution and covered with 

 K-inch-mesh wire cloth were distributed about the barns (10 per barn), 

 and the solution was replaced weekly. The use of such baits consti- 

 tutes a hazard to man and animals and is not recommended at this time. 



TEPP, malathion, Diazinon, and Bayer L 13/59 also were effective 

 when used at concentrations of 0.05 and 0.1 percent in water con- 



