Original article

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

¹ Centro de Estudos Florestais (CEF), Instituto Superior de Agronomia (ISA), Technical University of Lisbon (UTL), 1349-017 Lisbon, PT, Portugal
² CENSE, Dep de ciências e Engenharia do Ambiente (DCEA), Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, PT, Portugal

^* Corresponding author: mrbranco@isa.utl.pt

Received: 27 July 2009
Accepted: 1 December 2009

Abstract

• 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.