Browning foliage and needle drop are the primary symptoms


A spruce exhibiting discoloration and loss of foliage as a result of needlecast.

A broad range of fungal diseases that cause foliar discoloration and needle loss in conifers are known as needlecasts and needle blights. While visually unappealing, these diseases rarely lead to tree mortality on their own. However, they do reduce plant vigor, making affected trees more susceptible to pests and other problems.

Conditions

These needle diseases tend to thrive in wet weather conditions, shaded environments, and areas where trees are growing close together. Plants living outside of their natural ranges are more likely to be impacted, and young specimens are often more susceptible to damage than well-established trees.

Symptoms

Discolored needles
Discoloration of two-year old needles on an Austrian pine.
Non-uniform discoloration of Douglas fir needles
Non-uniform discoloration of Douglas-fir needles.

Browning foliage and needle drop are the primary symptoms of needlecasts and needle blights. Discoloration tends to develop in blotches or bands, rather than changing color uniformly. Noticeable browning and needle drop have generally occurred by mid-summer. Upon close inspection (magnification may be needed), small fungal fruiting structures may be seen on infected needles.

Depending on the lifecycle of the specific disease, discoloration and needle loss symptoms may first appear on the current year's growth (at the branch tips) or on two-year old needles (while growth at the tips remains green).

Control

Avoid overcrowding of trees and prune to allow for air circulation and light penetration within the canopies of conifers. This reduces damp conditions, where these needle diseases thrive.

Infections can generally be controlled with properly applied fungicide treatments. Timing varies depending on which needle disease is causing the problem. Also, proper irrigation, mulching, and fertilization as needed are recommended to help improve overall plant resilience.

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Leesburg , VA 20177

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