Timing matters: release of plant volatiles that are attractive to parasitoids

Many plant species are known to release volatile organic compounds (VOCs) in response to attack by herbivores to defend themselves by attracting natural enemies of herbivores. However, herbivores may not stay on a single plant, but may move among plants. We tested the flight response of female parasitoids to volatiles released from plants that are attacked by their host herbivores under laboratory conditions. Parasitoids significantly preferred plants that had been under attack by herbivores (currently attacked plants) over intact plants. After removal of the larvae, the plants (formerly attacked plants) were still significantly preferred by parasitoids over intact plants. Moreover, the parasitoids significantly preferred currently attacked plants to formerly attacked plants, suggesting that parasitoids may use VOCs specifically released from plants under attack to efficiently search for their hosts.