26 



Hansens and Anderson (1970) found that a ]% solution of the follow- 

 ing insecticides failed to give satisfactory fly control when applied 



as contact residuals: dimethoate, ronnel , stirofos, and bromophos. 



TM 

 Ficam gave good results as a contact residual against house flies. 



Sucrose was added to the solution to improve the knockdown. No resis- 

 tance data are available (Lemon and Bromilow, 1977) - 

 Synthetic pyrethroids 



The first synthetic pyrethroid to be synthesized was allethrin 

 (Schechter et al., 19^9) followed by resmethrin (Elliot et al., 1965). 

 Although natural pyrethrins are known for their quick knockdown (O'Brien, 

 1967), resmethrin proved to be 55 times more toxic to adult females of 

 M. domestiaa than mixed esters of natural pyrethrins (Elliot et al., 

 1967). Haskins et al . (197M claim resmethrin to be effective as a 

 contact residual, but Ma this et al. (1972) claim the opposite. Syner- 

 gised resmethrin had increased toxicity against resistant flies and the 

 synergist prevented knockdown recovery (Schulze and Hansens, 1 968 ) . 



Decamethrin is a highly toxic pyrethroid ester with an acute oral 

 LD-- for Female rats of 31 mg/kg. It can be rapidly absorbed by in- 

 halation (Kavlock et al., 1979). 



Permethrin is more effective at lower temperatures (Harris and 

 Kinoshita, 1977). Half life of permethrin in soils with low and high 

 organic content was 7 and 16 weeks respectively, with the loss of in- 

 secticide being attributed to microbial action (Williams and Brown, 

 1979). As in insects, the ci s-permethr in isomer was more toxic to 

 aquatic arthropods than the trans-isomer (Zitko et al., 1979). 



