Hafiz Azhar Ali Khan1. 1. Institute of Agricultural Sciences, University of the Punjab, Lahore, Pakistan.
Abstract
BACKGROUND: Permethrin (a pyrethroid) has been recommended for the management of a number of insect pests, including Musca domestica. Recently, resistance to permethrin has been reported from the Punjab province, Pakistan, which necessitates the need to manage the resistance problem. For this reason, a field strain of M. domestica was selected with permethrin for ten consecutive generations (G1-G10) to determine the risk assessment, the rapidity with which permethrin resistance can develop, and the presence or absence of the cross-resistance phenomenon. RESULTS: The results revealed that permethrin resistance increased very quickly in response to selection experiments. The resistance ratio (RR) value increased by 16.04- to 605.92-fold and the LD50 value increased by 100.22 to 3787.08 ng fly-1 after selection experiments. Moreover, the increase in LD50 value remained stable when the selected strain (Perm-SEL) was cultured in the absence of permethrin for the next five generations (G11-G15). The results revealed the possibility of minor cross-resistance in the Perm-SEL strain with β-cyfluthrin and deltamethrin, and lack of cross-resistance with imidacloprid and spinosad. The realized heritability (h2 ) value for the Perm-SEL strain was 0.23. Assuming a mean slope value of 1.27 and an h2 value of 0.23, then ten to four generations would be estimated for a 10-fold increase in the LD50 values at 50-90% selection intensity, respectively. CONCLUSION: The results of present study revealed high risk for permethrin resistance development under continuous selection pressure. Permethrin resistance developed very quickly under laboratory conditions, which might reflect the likelihood of resistance evolution in field conditions if permethrin selection pressure holds for a long time.
BACKGROUND:Permethrin (a pyrethroid) has been recommended for the management of a number of insect pests, including Musca domestica. Recently, resistance to permethrin has been reported from the Punjab province, Pakistan, which necessitates the need to manage the resistance problem. For this reason, a field strain of M. domestica was selected with permethrin for ten consecutive generations (G1-G10) to determine the risk assessment, the rapidity with which permethrin resistance can develop, and the presence or absence of the cross-resistance phenomenon. RESULTS: The results revealed that permethrin resistance increased very quickly in response to selection experiments. The resistance ratio (RR) value increased by 16.04- to 605.92-fold and the LD50 value increased by 100.22 to 3787.08 ng fly-1 after selection experiments. Moreover, the increase in LD50 value remained stable when the selected strain (Perm-SEL) was cultured in the absence of permethrin for the next five generations (G11-G15). The results revealed the possibility of minor cross-resistance in the Perm-SEL strain with β-cyfluthrin and deltamethrin, and lack of cross-resistance with imidacloprid and spinosad. The realized heritability (h2 ) value for the Perm-SEL strain was 0.23. Assuming a mean slope value of 1.27 and an h2 value of 0.23, then ten to four generations would be estimated for a 10-fold increase in the LD50 values at 50-90% selection intensity, respectively. CONCLUSION: The results of present study revealed high risk for permethrin resistance development under continuous selection pressure. Permethrin resistance developed very quickly under laboratory conditions, which might reflect the likelihood of resistance evolution in field conditions if permethrin selection pressure holds for a long time.