Effect of defoliator insect on growth and wood properties of eucalypt trees

Attack by defoliator insects reduces wood production and may affect quality. The objective of this work was to evaluate the tree growth, chemical, physical and anatomical properties of 5-year-old Eucalyptus grandis x Eucalyptus urophylla wood, both sound and attacked by Gonipterus platensis (Coleoptera: Curculionidae) and Thyrinteina arnobia (Lepidoptera: Geometridae). Eucalypt pulpwood-class trees were collected in commercial areas attacked by both defoliator insects in Itarare and Lencois Paulistas, Sao Paulo, Brazil. Attacks by G. platensis reduced tree height growth, decreased the mean annual increment, increased pentosans content, but did not affect basic density and anatomical characteristics. Attacks by T. arnobia reduced the cell wall thickness, basic density, insoluble and total lignin, and ash content. The radial profile of trees attacked by T. arnobia expressed lower air-dry density when compared to sound ones. The intensity of the effects on wood depends on the season, length of time, and severity of the attack. The alterations on tree growth and wood properties due to defoliation may jeopardize the final use of the wood product. As the studied trees were destined for pulpwood and paper production, important variables like wood consumption, yield of pulp, and pulpwood properties would be compromised.