Water stress affects Tomicus destruens host pine preference and performance during the shoot feeding phase

The effect of water stress on host selection and performance during the shoot feeding phase, by the Mediterranean pine shoot beetle Tomicus destruens, was studied. • Young potted Pinus pinaster plants were subjected to two water supply regimes: (i) well watered; (ii) 4-5 months of moderate drought stress. Plant volatile organic compound (VOCs) emissions were collected by SPME and analysed by GC/MS. • In tests with paired plants, the number of holes and tunnels excavated by beetles in well watered pines was significantly larger than in stressed plants, whereas in no-choice tests no differences occurred. • Beetle survival was significantly higher on well watered, than on stressed pines (p = 0.006), while fat contents also increased (p = 0.09). • Plants could be assigned to treatments based on VOCs emissions, stressed pines emitting more myrcene and less β-pinene than well watered ones. • It is concluded that during the shoot feeding phase, T. destruens preferentially attacks non-stressed plants, in detriment of stressed ones, upon which a higher fitness is attained. • The role of pines VOCs emissions under moderate drought stress, in the host selection and colonization process by the pine shoot beetle, is discussed.