Growth and canopy traits affected by myrtle rust (Austropuccinia psidii Winter) in Eucalyptus grandis x Eucalyptus urophylla

Abstract

AbstractAustropuccinia psidii Winter, causal agent of myrtle rust, is one of the main pathogens in Eucalyptus plantations in Brazil. We investigated the effects of the pathogen on wood yield and light use efficiency (LUE) in a Eucalyptus grandis x Eucalyptus urophylla clone in a field trial at the end of a five‐year rotation. The study comprised two treatments that are commonly adopted by managers. One treatment with curative fungicide spray (Triadimenol 250 g l−1) seven months after planting and another with five preventive sprays of the same fungicide, from the 1st to 7th month age of saplings. At 5 years old, the control plots attained a mean annual increment of 35 m³ ha−1 yr−1, the curative and preventive treatments were 39 and 47 m³ ha−1 yr−1 (11% and 34% higher, respectively). LUE was also higher when fungicides were applied, 8% and 26% higher in curative and preventive treatments (1.06 and 1.24 g MJ−1) compared with the control plots (0.98 g MJ−1). To confirm the negative effect of rust at a larger scale, we tracked 102 inventory plots (from 1,234 ha) from 2 to 6 years old with the same clone, half infected and half with rust corrective control. Growth difference decreased with time, from an average of 41% at age 2%–5% at age 6. These results highlight the importance of managing myrtle rust in Eucalyptus plantations by selecting a disease‐tolerant genotype or adopting other strategies for disease control.