Researchers in Japan have reported the discovery of a naturally occurring compound that repels stinkbugs, a major nuisance for householders and crop farmers in the US and Japan. A modified version of the compound, isolated from a fungus, was twice as effective at low concentrations as the ‘gold standard’ for measuring insect repellency – naphthalene found in mothballs – and researchers are hopeful that it may lead to the first stinkbug repellent.
‘In 2005, in the Tohoku local area of Japan… the damage by stinkbugs [to rice crops] was estimated to be ¥3bn, about $40m,’ said lead researcher Hiromitsu Nakajima, at Tottori University in Japan. ‘This decrease in the price [due to a reduction of rice quality] affects the farmer’s income seriously and thus the stinkbug is a big threat to the Japanese farmers.’
The insects get their name from the ‘skunk-like’ odour they emit when crushed or disturbed. Farmers control them using a variety of pesticides, including neonicotinoids, organophosphates and pyrethroids. However, applying insecticides too often is environmentally damaging and leads to resistance, therefore attractants or repellants could potentially offer a promising alternative method to control the pests.
The fungus containing the active chemical – identified as 3-(4- methylfuran-3-yl)propan-1-ol – infects a common weed, the green foxtail plant, which also appears to protect the plant against pests and diseases. To monitor repellency, the researchers counted the numbers of bugs that entered or left bottles containing the compound and other acyl derivatives, one of which was reported to be twice as effective as naphthalene at 0.1mM (J Agric Food Chem, 2010, 58, 2882).
‘Fortunately this compound is reported to be a synthetic intermediate. And thus we can synthesise the chemical by… optimum methods [which] would be much easier and cheaper than to isolate it from the fungus,’ Nakajima says. He estimates it would take two to three years of safety testing before the compound could be available commercially.