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Forest Pests of North America
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Drought Injury

From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54

Hosts. – All conifers, especially young trees.

Distribution. – Dry aspects, shallow soils, and areas experiencing unusually low rainfall.

Damage. – Mild drought may be expressed only in reduced growth or early dormancy. More severe drought may result in foliage damage or even tree death.

Identification. – Growth cessation may be followed by witting or discoloration (chlorosis or reddening) of new foliage. If drought continues new foliage is shed and shoots die back to lateral buds (fig. 148). With continued drought, tree mortality may occur, usually following bark beetle attack in larger trees. Drought in seedlings can be diagnosed in part from examination of roots; few if any active root tips will be found.

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Figure 148 - Drought has caused branch
dieback in the crown of this Douglas-Fir.

Similar damages. – Conditions which cause general decline in trees often resemble drought damage. Root disease, bark beetle attack, some mechanical damages, and chronic needle cast or insect defoliation are all similar in general tree symptoms to drought.

References.

Bega, R. V. 1978. Diseases of Pacific Coast conifers. USDA For. Serv. Ag. Hndbk. No. 521, 206 p.

Boyce, J. S. 1961. Forest Pathology. McGraw-Hill Book Co., New York, NY. 572 p.

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