Sept 20 news feed on Fox News - dying trees in Lane County

Asked September 21, 2019, 1:43 PM EDT

Drought was stated as what caused the trees' death, only dying pine trees were pictured. No mention of the boring insects that kill pine trees, was that omission intentional? No pictures of dying deciduous trees either. I have seen dead pine trees in peoples' yards where their lawn is nice and green - they water the lawn and trees - yet the tree is dead. Is drought or boring insects the reason for so many dead pine trees in Lane County?

Lane County Oregon

1 Response

Both evergreen and deciduous trees have been suffering from drought conditions over the 2015-2018 summers. Dead trees you notice this summer likely died last summer or fall and didn't finish drying out until this summer. The main driver of this mortality is the drought conditions. Longer periods through the summer without rain in addition to multiple weeks in a row with over 90 degree weather is really difficult on the tubes in the trees that bring water from the roots into the leaves. Under the right conditions, this stress alone can kill the trees. Insects in this case are secondary. They are not driving the mortality of these trees. The beetles can "sense" the stress these trees are under and because their defense systems are weakened by the drought then they cannot fight off the insects. The trees are then not able to handle both drought and the insect attack together and the tree dies. So, insects are part of the story, but they aren't the reason for the dying trees.

Trees that are watered in lawns are likely dying because of the way lawns are watered. More water over shorter periods of time doesn't allow the water to get deep into the soil where the tree roots are and most of the water gets taken up by the grass roots. Trees need watering that is little water over extended periods of time so that the water gets deep in the soil and there is enough to feed both the grass and the trees.