Impact of Teratosphaeria nubilosa over tree growth and survival of Eucalyptus globulus and Eucalyptus maidenii in Uruguay

Teratosphaeria nubilosa severely affects young plantations of Eucalyptus globulus and Eucalyptus maidenii in Uruguay. This work analyzes the effect of the damage caused by T. nubilosa on tree growth and survival of E. globulus and E. maidenii, based on data from a trial naturally infected by this pathogen. The effect of defoliation and proportion of adult foliage on tree growth and mortality was evaluated at 50 months of age. Defoliation in E. globulus was higher than in E. maidenii, reaching average values of 52.5 and 28.8 %, respectively, at 21 months of age. By contrast, E. globulus showed higher precocity of vegetative phase change than E. maidenii. Although the damage threshold for diameter growth was 40 % on E. globulus and 20 % on E. maidenii, the detrimental effect on growth was similar in both species, where the most defoliated trees suffered a reduction in diameter of 49.4 and 47.5 %, respectively, at 50 months of age. Mortality increased significantly when defoliation exceeded 30 % in E. globulus and 40 % in E. maidenii. The results showed that E. maidenii has lower defoliation, higher growth and lower mortality than E. globulus after epidemics of T. nubilosa. However, the lower defoliation and higher proportion of juvenile foliage showed by E. maidenii represent a greater source of inoculum, suggesting that a large-scale replacement of E. globulus by E. maidenii in areas where T. nubilosa is a problem could be risky from an epidemiological point of view.