Abstract
An outbreak of the brown wheat mite, Petrobia latens (Müller), occurred on carrot cultivated in greenhouses of Tokushima Prefecture, Shikoku Island, southern Japan, in early spring of 2011. It caused a serious reduction of yield, because effective methods to control this mite were lacking. The present study determined the susceptibility of P. latens to 22 agricultural chemicals, including three physical control agents (thought to block the target organism’s spiracles) and two granulates, because chemicals will be used as the first line of pest control. When adult females of P. latens were treated with recommended concentrations of the chemicals, seven out of 17 pesticides and fungicides — i.e., bifenazate, DBEDC, emamectin benzoate, lepimectin, methomyl, milbemectin and pyridaben — caused 95-100% mortality after 96 h (lepimectin, methomyl and mibemectin caused 90-100% mortality even after 24 h). The three physical control agents had no effect on the adult females. The two granulates were also tested for an ovicidal effect against diapause eggs of P. latens. It appeared that only diazinon had a negative effect on egg hatching (ca. 45% reduction relative to control). These results suggest that this species could be controlled, in principle, with any of seven effective chemicals as a first method. Two of these seven chemicals — emamectin benzoate and methomyl — are registered as pesticides for carrot crops.
