Relationship between Pyrethroid Resistance and Attacking Persimmon in the Onion Thrips, Thrips tabaci (Thysanoptera: Thripidae)

Abstract

To detect biological differences between pyrethroid-resistant strains and pyrethroid-susceptible strains of the onion thrips, Thrips tabaci, developmental and ovipositional characteristics on the leaves of 5 varieties of persimmon and green bean were investigated by rearing trials using isofemale lines. In addition, suitability of 2 varieties of persimmon fruits as foods for thrips larvae was compared between a pyrethroid-resistant strain and a pyrethroid-susceptible strain of onion thrips. Irrespective of susceptibility levels to pyrethroid, while T. tabaci adults deposited eggs into persimmon leaves, few individuals completed larval development on the leaves, suggesting that T. tabaci does not develop on persimmon leaf throughout reproductive seasons. Both strains of T. tabaci successfully molted into adults when they fed on persimmon fruits, but survival rates in immature stages differed among varieties and developmental stages of the fruits. These differences may cause inter-specific and seasonal variation in injury levels by thrips attacking persimmon orchards. The pyrethroid-resistant strains showed lower fecundities compared to the pyrethroid-susceptible strains of onion thrips on green bean leaf. In conclusion, there was no evidence that unique characteristics other than susceptibility levels to pyrethroid insecticide contribute to pestilent levels of the onion thrips in commercial persimmon orchards.