Why Is My Pine Tree Losing Its Needles?

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For all the benefits pine trees can offer, they also suffer from their share of problems.

One of the most common and most vexing is when your pine tree starts losing its needles.

When this happens, it can spell the death of the tree.

Unlike the leaves on deciduous trees, pine trees never regrow their needles. If the tree loses too many, it won’t be able to survive.

Therefore, it’s important to spot and treat problems before they prove fatal to your tree.

Here are some of the common reasons that pines lose their needles, and what you can do to prevent them, or reverse their effects.


Needle Blight

pine needle blight
Photo by Joseph O’Brien, USDA Forest Service, Bugwood.org, via Wikimedia Commons

What is it? Dothistroma needle blight and diplodia tip blight (also known as Sphaeropsis blight) are caused by certain fungi.

When infected, the tree will show less vigorous needle development and yellowing or browning of newer needles.

When it gets into a wound on the trunk, it can also cause girdling.

The fungi that cause these diseases prefers wet, cool springtime conditions and takes advantage of injured trees.

What to do: Restrict pruning to the winter when the fungus isn’t present.

Regular and thorough watering will help the tree be more resistant to problems.

If infection should occur, using a strong fungicide is recommended.


Pine Wilt

Austrian Pine with pine wilt
Part of Austrian Pine with pine wilt. Photo via CC Wikimedia commons

What is it? This fatal condition is caused by a certain roundworm species called the pine wilt nematode.

This tiny, destructive worm eats the pine tree’s cells, causing it to wilt from an inability to transport water and nutrients.

However, this nematode isn’t like the others.

Unlike most of its soil-dwelling brethren, the pine wilt nematode infects the upper parts of the tree.

What to do: Once a tree is infected with these pests, they can be spread to nearby healthy trees.

Any tree with pine wilt should be removed and burned.

If you really want to save the tree, nematicides are available, but they are expensive.


Pine Bark Beetle

bark beetle larva labyrinths
Bark beetle larva labrynths, via Wikimedia Commons

What is it? These insects tend to infest ailing pine trees and aren’t picky about which pine species they exploit.

These destructive pests burrow into the bark, hindering the tree’s ability to transport nourishment and water.

There are multiple species of pine bark beetle, but they all affect pines the same way.

What to do: Check the bark for squiggly lines, check the needles for browning, shedding and inspect the branches for signs of death.

Keeping pines watered and fed properly will help them resist infection and degradation.

Infected pines should be removed and burned to prevent additional infestations.


Phytophthora Root Rot

Pine tree infected with Phytophthora cinnamomi
The tree on the right is infected with Phytophthora cinnamomi, the tree on the left shows no symptoms of infection. Photo by Jeffrey J. Witcosky, USDA Forest Service via Wikimedia Commons

What is it? This soil-borne fungus tends to infect pine trees, harming or killing them in the process.

Although this fungus lives in the soil, the symptoms are presented on the above-ground portions.

Signs of an infection include reduced growth, reddening or browning needles, dying branches, falling needles and eventually, death.

What to do: The fungus is common in soil with poor drainage, wet soil and warm temperatures.

It can be prevented by planting your trees in well-drained locations.

Professional soil tests from your local tree care company or university agricultural extension can tell you if this fungus is present in your soil.

If infection occurs, commercial fungicides are often helpful.

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