Diagnosis of acaricide resistance in Oligonychus punicae (Hirst) (Acari: Tetranychidae) in grapevines from the São Francisco Valley, Brazil.

Abstract

The intensive use of acaricides, such as abamectin, in the S˜ao Francisco Valley region of Brazil has increased selection pressure on the red mite Oligonychus punicae, leading to frequent reports of field control failures. This study evaluated the hypothesis that repeated abamectin use for tetranychid mite control in grapevines has led to a high frequency of resistance in O. punicae populations. This study aimed to detect and document abamectin resistance in O. punicae populations infesting grapevines. To assess potential cross-resistance, toxicity assays were also conducted with bifenthrin and pyridaben—other acaricides registered for Tetranychus urticae control in Brazilian vineyards. Tested populations of O. punicae exposed to a diagnostic concentration of 9 mg L 1 aba- mectin were classified as resistant, with resistance ratios reaching up to 398-fold relative to the susceptible population. In contrast, the label-recommended concentrations of bifenthrin and pyridaben caused 100 % mortality in all tested populations, although resistance ratios varied from 1- to 25-fold. A significant positive correlation was observed between the LC90 values of abamectin and bifenthrin; however, the results suggest a pattern of multiple resistance rather than cross-resistance among the tested acaricides. Understanding the evo- lution of acaricide resistance in O. punicae is essential for developing effective pest control and resistance management strategies in viticulture