Realized heritability of resistance to deltamethrin in a field strain of Musca domestica Linnaeus (Diptera: Muscidae).

A deltamethrin selected field strain of the house fly, Musca domestica, was used to assess realized heritability (h) and risk for resistance development to deltamethrin. The estimated value of h was 0.27 with phenotypic standard deviation σ = 0.56 and selection differential S = 0.64. The intensity of deltamethrin selection had a direct effect on the rate of resistance development in the selected strain. Assuming the h value = 0.27 for six generations under selection pressure, a tenfold increase in the LC values has been expected in only 8-4 generations at the selection intensity 50-90%, respectively. In conclusion, the estimated values of h and the projected rate of deltamethrin resistance revealed a strong and rapid potential of the M. domestica strain to develop resistance against deltamethrin. Therefore, this insecticide should be used cautiously in the field.