DIAGNÓSTICO FITOPATOLÓGICO DE LAS PRINCIPALES ENFERMEDADES EN DIVERSAS ESPECIES DE ENCINOS Y SU DISTRIBUCIÓN EN LA SIERRA FRÍA DE AGUASCALIENTES, MÉXICO

Abstract

Oak trees (Quercus spp.) are a very important
resource for mankind. For several years oak
mortality has been observed on the Sierra Fría,
Aguascalientes, Mexico. The objectives of this
study were: 1) to know those agents causing
oak mortality on the Sierra Fría, 2) to establish
the distribution of affected areas on this sierra,
3) to determine oak species affected in the area
of study and 4) to indicate their importance as a
plant pathogens. Twenty-eight locations on the
Sierra Fría were sampled by means of transects.
Each transect comprised a visual inspection
of 20 trees to observe symptoms and signs
on affected trees. In addition, 100 trees were
inspected at each location in order to detect
ascomata and basidiomata of plant pathogens.
The identification of plant pathogens was based upon the presence of symptoms and signs
(ascomata, basidiomata) on the trees. Cankers
were the most important observed symptom,
being present in 92% of study locations and
on 15 to 75% of trees. On living and mature
oak trees, the plant pathogens causing the
cankers were: Phellinus robustus, P. gilvus and
P. everhartii. Ganoderma lucidum was found
on both young and adult trees. Biscogniauxia
atropunctata and Hypoxylon thouarsianum,
opportunistic fungi of low pathogenic capacity, were also identified, affecting weak trees
stressed by abiotic factors (drought, frost) and
other plant pathogens. The most abundant
oak species, and the one most affected, was
Q. potosina. Hypoxylon thouarsianum was
the most widespread fungus, being present
in 12 out of the 28 study locations, followed
by B. atropunctata, which was found in eight
locations.