Diseases of pine trees; learn about pine needle casting.
What is it?
This pine tree plant disease is caused by one of two species of fungi. The culprits are either hypoderma lethale or lophodermium pinastri. Both young and old pine trees may be affected, but the disease damage seems to be most prevalent and severe among younger pines.
What does it look like?
Pine needle cast causes the tips of the needles of the prior year's growth to turn brown over the winter. By the coming of spring, these diseased needles are completely discolored and the pine tree may have an overall scorched look to it. Often all these old discolored needles, or a large number of them will drop from the tree altogether in spring, which leaves only the new green needle growth. Often the needles which do not drop will develop tiny, elongated black structures along the mid-section of individual needles and may become swollen, eventually developing cracks down the middle.
How does it manifest?
Splashing rain or other water sources, and wind often carry the fungal spores to healthy pine tree needles. It is at this time that the fungi enter the tips of needles, but it is rare to see any damage from pine needle cast until the following spring. March or April may be your first sight of pine needle cast, as tips of needles turn yellowish, then brown and eventually blackish if they manage to survive drop off. Occasionally, damage will be so sever that the branch tips themselves die back and spores from this then re-infect the healthy needles and start the cycle of damage and death again.
What can you do about it?
The most shaded areas of the pine tree will be most prone to developing pine needle cast as it is a perfect environment for the fungi to thrive. Once you note a serious spring eruption of pine needle cast, spray the tree in late July with a chlorothalonil containing fungicide. Do this again in early September, repeating regularly at intervals of ten days to two weeks. To avoid further damage to shaded trees, you can remove any shade-producing structures or overlapping branches to help destroy a prime fungal breeding environment.
