IMPACT OF Chrysoporthe cubensis (Bruner) Gryzenhout & M. J. Wingfield IN TWO SEED PRODUCTION AREAS OF Eucalyptus urophylla S. T. Blake IN SANTIAGO YAVEO, OAXACA

Abstract

Plantaciones Tehuantepec (Planteh) company established in Santiago Yaveo, Oaxaca, two six-years-old seed areas of Eucalyptus urophylla for production of improved seed aimed for pulp production. Chrysoporthe cubensis, a fungus that causes stem cankers on eucalypts, affects its growth. The main management option for this pathogen is the selection and use of resistant genotypes. In order to observe the evolution of the disease in left standing trees normal diameter and the fungus incidence in August 2007 were assessed before setting the seed areas. A year later, after the selection of superior trees and thinning the undersized, around 10% of the original population remained. In August 2008, the above parameters as well as the severity were evaluated. In addition, samples of bark were analyzed to detect the sexual or asexual stage of the fungus. The incidence before setting the seed areas was 15.4%, The incidence before setting seed areas was 15.4%, but there were sites with more than 20%. After the removal of all diseased trees, at 12 months, 58.1% of individuals remained healthy, 28.0% with undetectable damage, 9.5% slightly damaged, 3.0% with moderate damage, and 1.4% with noticeable damage. It was observed that the fungus is present in both phases, indicating that the sexual fungus can create greater genetic variability, can recreate genetic variability, which represents a severe problem for these plantations if further expansion occurs.