Time and frequency of thiamethoxam application for control of Japanese gall-forming thrips, Ponticulothrips diospyrosi (Thysanoptera: Phlaeothripidae) on persimmon

Ponticulothrips diospyrosi Haga et Okajima has several characteristic features of damage, such as leaf rolling and dotted scars on fruit skin. The objectives of this study were to find out the optimum timing and frequency of insecticide application to reduce this damage. The effect of spraying twice at a 7-day interval before adult immigration was tested. The efficacy of the insecticide was delayed by the favorable microhabitat produced by adults and offspring within damaged leaf. Twice spraying in 2005 was effective in reducing the number of surviving insects and damaged leaves 1 month later. The time of adult immigration was coincident with the growth of persimmon shoots to 2 cm approximately, or the stage of four to five leaves, on April 22. Spraying three times in 2006 was the most effective, starting the first spray at the five to six leaf stage, immediately before immigration, and the second 9 days later (on immigration), and the third after the flowers faded. By using this control regime, no leaves were damaged, and residues of thiamethoxam and its metabolite were trace levelled when they were analysed by HPLC in late October. The growers could obtain the highest portion of marketable fruits, > 99%, yielding an acceptable net income.