My pine tree has me concerned. There are a bunch of needles that are turning brown. Is something wrong? SH

Browning needles are not usually cause for concern unless they are. Let me explain.

Pines are considered “evergreens”, but evergreens can still lose needles this time of year. Each year, pines grow from the tips of their branches, generating new needles as they grow. As the branch grows, the newer needles are at the tips of the branches, while the older needles remain back up the branch a bit. As the growth continues, the older needles get shaded and subsequently become less active, eventually turning brown and dropping off. These needles that drop to the ground are a great source of mulch for your garden.

Each season, a pine tree can lose up to one third of their needles in this very natural and expected way. In a healthy tree, the needles that drop are located more toward the interior of the tree. However, if you have browning needles in both the interior and outer edges of your pine tree, this is indicative of something known as pine wilt disease.

Pine wilt disease is the result of a roundworm known as the pinewood nematode. Nematodes are microscopic, meaning you can’t see them with the naked eye but they can do a lot of damage. The problem is that these nematodes feed on the water-conducting cells (xylem) in the pine tree. As their feeding progresses, they disrupt the flow of water and nutrients within the tree, Unfortunately, this results in the death of the tree. If nematodes are the problem, tree decline, and death happen pretty quick. Declining pines become susceptible to a blue-stain fungi which enables the nematodes to persist in a dead tree. When cutting down a dead pine tree, you will likely see some portions of the wood with a bluish tint. This is the blue-stain fungi.

While the nematodes are not able to move from tree to tree on their own, they do hitch a ride on the Pine Sawyer Beetle. Pine sawyer beetles like to lay their eggs in dead or declining pine trees. To do this they chew a hole in the bark and place their eggs inside that hole. As the larvae feed, they work their way back out toward the outer surface of the tree. When an adult pine sawyer beetle eventually emerges, the nematodes move into the respiratory opening of the adult beetle. When the beetle moves to another tree, the nematode hitch a ride to a new host tree and the process starts all over again.

Unfortunately, once a tree is infected with nematodes, there is no cure. Because of this, dead pine trees should be removed as soon as possible to help minimize the chance of nematode damage in other trees.

So, the bottom line is that if your needles are browning toward the middle of the tree and dropping to the ground, this is likely normal needle drop. However, if the pine is rapidly turning brown all over, it’s likely you are going to lose the tree. Good luck.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Ladd Livingston, Idaho Department of Lands, Bugwood.org