259 



factors of 10 and 86 respectively. The mite strains tested by Hall 

 et al . (1978) were more resistant than the Florida strains, especially 

 to malathion. 



Slopes for all compounds tested were less than ®ne (Table 55). 

 Carbaryl and malathion had the flattest slopes indicating that concen- 

 trations necessary to achieve 100% kill in the field would have to be 

 much higher than concentrations of the permethrins required to elicit th« 

 same rate of response. The slopes of compounds tested by Hall et al. 

 (1978) were slightly steeper indicating that the susceptibilities of 

 their mite strains to the acaricides were more homogeneous than the 

 Florida strains (Hoskins and Gordon, 1956). In summary, Florida strains 

 of mites are not as resistant as the strains tested by Hall et al. 

 (1978), but the shallow slopes of the regression equations indicate 

 that resistance may be building within the Florida strains. 



In field tests, Ravap gave practically 100% control of mites in 

 2 weeks. Carbaryl and malathion produced the same results in k and 6 

 weeks respectively. Control with Ravap was probably due in part to 

 the vaporizing action of Vapona. Loomis et al. (1970) got poor mite 

 control on hens with a 0.5* carbaryl solution, but Hall et al. (1978) 

 got 100% control within 2k hr using the same concentration. Several 

 reports of suspected malathion resistance (Foulk and Matthysse, 1963; 

 Rodriguez and Riehl, 1963) preceded the confirmation of resistance by 

 Hall et al. (1978). Many resistance claims are a result of poor appli- 

 cation methods (Eleazer, 1978) for which the poultry industry is 

 notorious. This was not the case with the experiments at the tilling 

 site, since hens were sprayed more thoroughly than could be expected 

 under normal conditions. 



