190 



Testing continued in 1978. Mortality was 50% on 9 June and dropped 

 to 2.5% by 3 August. At this point the experiment was terminated. 

 Permethrin at 0.05% was effective on wood for almost 23 months. 



Fluctuation of control mortality throughout the experiment can 

 only be attributed to an interaction between the flies and the un- 

 treated template surfaces. 



Synthetic pyrethroids as contact residuals in the field. Three 

 synthetic pyrethroid compounds, SD ^3775 (Shell Development Co., 25% WP 

 and 10% EC), BW 21Z (Burroughs Wellcome Co., 25% WP and ^+2.5% EC), and 

 ICI 1^3 (ICI Americas, Inc., 5% EC), were applied to wooden panels in 

 the amounts shown in Table 52. 



Several weeks after panels were installed at the tilling site, 

 there was no evidence to indicate that the compounds were killing flies 

 as no dead flies were found in the aluminum guttering. In order to 

 test the efficacy of the compounds, 3" to 5 _ day-old female laboratory 

 colony house flies were processed and exposed to panel surfaces in the 

 following manner. Flies were sexed while anesthetized with CO2 and 

 placed 10 to a cage in cages made from 180-ml plastic cups with lids. 

 Cup bottoms had been removed and replaced with disks of window screen. 

 In the field, cages were slipped under 23~cm lengths of 3~cm wide 

 elastic that had been stapled to the panels for the purpose of holding 

 the cages tightly to the surface. Lids were removed as cages were 

 secured on the panels. One cage was attached to each panel for a 24-hr 

 period. Criterion for death was total lack of movement. 



Resul ts. All compounds produced mortality rates up to 100% at 121 

 days post-treatment (Table 53). Knockdown was usually within 15 min 

 though the onset of death required a much longer period. Flies fluttered 



