Determination of Spiromesifen+Abamectin, Spirodiclofen, Milbemectin Resistance Levels of Pest Tetranychus urticae Koch (Acarina:Tetranychidae) Populations in Isparta Apple Orchards

Abstract

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is one of the important pests that cause economic losses in apple orchards. Due to their short-term biology, they develop resistance to acaricides used in a very short time. Therefore, for an effective chemical control, the susceptibility levels of T. urticae populations to acaricides should be monitored periodically. In this study, resistance rates of 10 different T. urticae populations collected from areas with intensive apple production in Isparta province and its districts against spiromesifen + abamectin mixture, spirodiclofen and milbemectin were determined. In order to determine whether these populations are resistant to spiromesifen + abamectin, spirodiclofen and milbemectin, first of all, the LC50 and LC90 values of the susceptible green form (German susceptible strain; GSS) population of T. urticae were determined by spray tower-leaf disc method. The LC90 value determined in the susceptible population was accepted as the differential dose and applied to the collected T. urticae populations to determine whether there was resistance. Populations with less than 80% mortality at the differential dose were considered resistant and LC50 values were determined. Resistance rates were found by dividing the LC50 values of these orchard populations to the LC50 value of the susceptible population. According to the diagnostic dose, 6 populations from 10 T. urticae populations collected from apple orchards to the spirmesifen + abamectin mixture, 6 populations to spirodiclofen and 3 populations to milbemectin were developed resistance. The LC50 values of these orchard populations ranged from 1.01-168.35 mg a.i. l-1 for spiromesifen + abamectin mixture, 0.43-3.32 mg a.i. l-1 for spirodiclofen, and 1.41-2.79 mg a.i. l-1 for milbemectin. The resistance rates were 1.89 - 315.31 fold for spiromesifen + abamectin mixture, 6.49 - 13.01 fold for spirodiclofen, 2.98 - 5.89 fold for milbemectin. According to these results, some populations started to develop resistance to the spiromesifen + abamectin mixture, while resistance developed in some populations. Cross-resistance has also developed in spirodiclofen and milbemectin in populations resistant to the spiromesifen+abamectin mixture.