Response of Predatory Insect Scolothrips takahashii Toward Herbivore-Induced Plant Volatiles Under Laboratory and Field Conditions

We studied the response of a predatory thrips, Scolothrips takahashii, towards herbivore-induced plant volatiles emitted by Lima bean plants infested by two-spotted spider mites Tetranychus urticae (green form). Tests were conducted with a Y-tube olfactometer in the laboratory and with traps under field conditions. The odor of artificially damaged and uninfested Lima bean leaves was not more attractive than clean air in the Y-tube olfactometer. The predatory insects showed a greater preference for Lima bean leaves infested by the two-spotted spider mites than for either clean air or uninfested bean leaves. They showed the same preference towards infested leaves from which all spider mites and their visible products had been removed. Neither the spider mites themselves nor their products attracted the predators. In a satsuma mandarin grove, two traps with infested Lima bean plants as an odor source attracted 42 adult S. takahashii in 55 days, whereas no S. takahashii were trapped in two control traps with uninfested Lima bean plants during the same period. No S. takahashii were found during this period in the vicinity of either the sample traps or the control traps (5-m radius of each trap). These data showed that S. takahashii use herbivore-induced plant volatiles in their foraging behavior in natural ecosystems.