Impact of Ceratocystis wilt on eucalyptus tree growth and cellulose pulp yield

Abstract

In this study, we determined the effects of Ceratocystis fimbriata wilt on volumetric growth and cellulose pulp yield of eucalyptus. Seven‐year‐old healthy and infected trees were separated into different classes of severity, and the individual volume of each whole tree with bark was determined. Volumetric losses were found regardless of the class of disease severity, resulting in reduction in volumetric growth of the trees from 65% to 87%, depending on the infection level. Two approaches were used for evaluating the effects of the disease on cellulose pulp yield: (i) evaluation of wood basic density and chemical composition, contents of ethanol/toluene extractives and Klason lignin, and the alkaline load and screen yield across Kraft pulping to kappa number 18 ± 0.5 for both healthy and discoloured materials; (ii) determination of the alkaline load and yield across Kraft pulping to kappa number 18 ± 0.5 of woods with different levels of discoloration (0, 25, 50, 75 and 100% of discoloured wood). Discoloured wood presented lower basic density, higher ethanol/toluene extractives and Klason lignin, higher alkaline load and lower pulp screened yield at kappa number 18 ± 0.5 compared with the healthy ones. Increasing the fraction of infected wood in chip furnishes resulted in proportionally increased alkaline load demand and decreased screen yields. Adding 50% of infected wood in the chip furnish resulted in 23.8% increase in the alkali load and 13.7% reduction in the pulp screen yield at kappa number 18 ± 0.5. The results obtained have proved that the disease reduces volumetric growth, increases wood consumption and reduces yield in eucalyptus pulp production.