The effect of synergists on the inhibition of detoxification enzyme activities and acaricide sensitivity in Rhizoglyphus robini.

Abstract

The saffron bulb mite, Rhizoglyphus robini Claparede (Acari: Acaridae), is the most important pest of the saffron crop in Iran. This pest attacks and feeds on saffron corms. For this reason, the corms are treated with acaricides before planting. The high activity of detoxification enzymes in arthropods may reduce their pesticide sensitivity. Diethyl maleate (DEM) is an inhibitor of glutathione S-transferases (GSTs), piperonyl butoxide (PBO) is an inhibitor of cytochrome P450 monooxygenases, and triphenyl phosphate (TPP) is an inhibitor of esterase activity. A filter paper method was used to determine the efficiency of these synergists in inhibiting the activity of detoxifying enzymes of R. robini. Adult mites were treated with these three synergists for 6, 12, 24, and 48 h, respectively. The activity of each detoxifying enzyme was measured and compared to the control treatment, and the inhibition percentage was calculated each time. The results showed that DEM reduced GST activity by 59.9% after 48 h, PBO inhibited cytochrome P450 activity by 30%, and TPP suppressed esterase activity by 38.5%. The most statistically significant inhibition occurred 24 h after pretreatment with each synergist. Bioassays with 24 h pretreatment showed that the sensitivity of R. robini to propargite increased by 1.6 times with PBO, 1.7 times with TPP, and 2.5 times with DEM. In conclusion, synergists and efficient inhibition of detoxifying enzymes can play a significant role in increasing the sensitivity of agricultural pests to pesticides and can be considered in managing pesticide resistance.