Surprisingly, resistance level of natural A. aegypti collected
recently (2008) in Araripina was higher (RR = 240) than the one
obtained for the RecR strain (R = 180) selected in laboratory. This
points out to an alarming situation in the field, revealing the inefficiency
of the control program that impose a high selective pressure
with temephos, without any routine evaluation of field efficacy of
commercial products. According to Montella et al. (2007), residual
effect of temephos-based larvicides (mortality >70%) in field populations
presenting high level resistance (RR > 10) can be shorter
(around 3 weeks) than the interval of treatment cycles (8 weeks).
It is important to highlight that many of these field populations
have been exposed to this OP and other insecticides for at least
13 years.