Although drought is often the cause, trees can die for other reasons besides lack of soil moisture, said Dr. Eric Taylor, Texas AgriLife Extension Service forestry specialist, Overton.
“Drought is the primary contributor to tree kill, but it may not be exactly the way you might be thinking,” Taylor said. “You may find this hard to believe, but relatively few trees likely died directly from dehydration in 2011. Instead, the 2011 drought severely weakened mature trees, making them susceptible to opportunistic pathogens like hypoxylon canker and insects like pine bark engraver beetles.”
He said that in most instances, the trees that died in 2011 were already stressed from a number of pre-existing environmental factors such as overcrowding, growing on the wrong site, age, soil compaction, trenching or inappropriate use of herbicides. If not for these factors, a large proportion of the trees that died might have recovered from the drought.
“This is an important concept to remember because our best defense against drought is to promote a tree’s health and vigor through proper care and management,” Taylor said.
From AgriLife Today: https://today.agrilife.org/2012/07/20/2011-tree-deaths/