Windbreaks under Stress

by Troy Bratton, District Forester
Kansas Forest Service
Dodge City, Kansas

The effects of the extremely dry conditions that have plagued many areas in southwest Kansas are showing up in many windbreaks. The lack of adequate rainfall has put windbreak trees under severe stress.

When trees are under stress for any reason, such as drought, tight spacing, hail or wind damage, root injury, or decline, they are more susceptible to insect or disease attacks. Trees have natural defenses to ward off harmful insect and disease organisms. For example, when the larvae of a boring insect attack a healthy tree, the tree’s sap flow can push the insect out of the tree.

Trees that are under stress have reduced natural defenses. Drought-stricken trees and trees under crowded conditions have limited sap flow and do not have the ability to defend against boring insects. It is important to keep in mind that most boring insects are considered secondary invaders and only invade under stressful conditions.

This is what we are seeing with the cedar trees in many windbreaks. The cedar trees have not been thinned and/or are under severe drought stress. Their natural defenses are low. Two opportunistic insects, flat-headed borers and cedar bark beetles, are attacking the trees and causing their death.

The best method of controlling these pests is to promote the health of the trees and to remove and destroy dead and dying trees in the windbreak. When we remove the dead and dying trees, we reduce the insect population that is harbored there. Thinning a windbreak to reduce competition and irrigating the windbreak are the two most beneficial practices for dealing with these opportunistic insects. It is recommended that professional assistance be obtained before a thinning operation is conducted. The borers are not the real problem; they are just the symptoms of the real problem - extremely dry conditions and overcrowding.

This article is also available in Microsoft Word format.

Windbreaks under Stress (DOC; 32 KB)

< Back to Conservation Editions - Fiscal Year 2005 Index

Last Modified: 09/04/2008