Many landowners throughout eastern Washington have noticed that some of the ponderosa pine in and around their stand look rather unhealthy this spring. From afar it appears as if these trees are dead or dying, but upon closer inspection, you may find that this is not the case.
Much of the current damage we are seeing in ponderosa pine is due to red band needle blight (i.e. Dothistroma Needle Blight). Red band needle blight is a fungus that infects the needles of ponderosa pine and lodgepole pine. Needles typically become infected in the spring during warm, moist weather. The first evidence of infection occurs in autumn in the form of a dark-colored band encircling the infected needle. The following spring (a year later), the tips of the needles that have been infected will turn yellow. If you look closely, you will notice that the bases of the infected needles are green, while the tips are yellow and in-between the two colors there is a dark band. By summer time, these needles will turn brown and drop prematurely. Although this damage looks concerning, red band needle blight rarely kills trees.
The needles on my pine tree are green at the base and yellow at the tip, but there is no banding
Damage similar to that of red band needle blight has also occurred over this past winter. It is believed that the damage being seen is due to temperature fluctuations. In October and November 2014, the temperatures were unusually warm for several weeks. The sudden dive into the teens overnight in mid-November may have killed the tips of ponderosa pine needles on some trees. This damage looks just like red band needle blight; needles are yellow at the tips and green at the base, but the band that typifies red band needle blight is absent.
My ponderosa pine has many dead tips
In addition to red band needle blight, a tip blight (Sphaeropsis) has also been prevalent in ponderosa pine. In the case of tip blight, you may see dead tips scattered throughout the crown of your pine tree. When you break open the buds on these tips, they will be dead. Additionally, the needles on these tips may appear stunted and there may be small, black dots on both the needles and stem. These black dots are the fungus’ fruiting bodies. Similar to red band needle blight, tip blight rarely causes mortality.
Damage caused by western gall rust can also result in dead tips scattered throughout the crown. Western gall rust can be differentiated from tip blight through the galls found on the branches of the dead tips. The galls kill the tips of branches by restricting the movement of water.
Should trees infected with red band needle blight, tip blight, or western gall rust be removed?
It is possible for ponderosa pine infected with any of these fungi to die if they are already stressed by some other factor such as drought or if they continue to be re-infected for several years in a row. Additionally, infected trees are sometimes attacked by bark beetles. But more than likely, these trees will re-foliate this spring and recover; therefore, it would be best to wait and see how your trees fare.
If you feel inclined to treat, there are several management techniques that may be helpful. Tip blight and gall rust infections can be pruned out. It is best to wait until fall to do your pruning, as volatiles from the cut branches may attract Ips bark beetles. If you have seedlings and saplings infected with western gall rust on the main stem, they will likely die, as stem galls typically girdle these smaller trees. In larger trees, a gall on the stem (often called a hip canker) may predispose trees to wind breakage. Trees with galls on the stem should be removed. If the site is droughty, you may want to consider watering infected trees if at all possible. Thinning is helpful in areas where trees are dense, as this allows the residual trees to obtain more water, sunlight, and nutrients. If you decide to thin your stand, focus on the least healthy trees for removal. For high value trees infected with red band needle blight or tip blight, fungicides can be used during budbreak to help protect against re-infection.
How do I know for sure bark beetles are not causing the damage I am seeing?
When bark beetles kill ponderosa pine, the needles typically turn red throughout the entire length of the crown. Additionally, the bases of the individual needles do not stay green when a tree is dying from bark beetle attack. Bark beetles also leave other telltale signs of their presence, such as pitch tubes and frass on the outside of the bark, and galleries under the bark. Pitch tubes form on the outer bark when the bark beetles attempt to bore into the tree. These pitch tubes are formed with resin, which can drown beetles as they attempt to gain access to the tree. Frass is a mixture of wood and beetle feces that is often seen on the cracks and crevices of the outer bark. Galleries are found under the bark and are tunnels formed by adult beetles and their larvae in the tree’s phloem (vascular tissue that conducts sugars and other metabolic products downward from the leaves).
If you have concerns or have further questions regarding the damage you are seeing on your ponderosa pines, contact a specialist at WSU or the Washington State DNR.
By Melissa Fischer, forest health specialist, Northeast Region, Washington State Department of Natural Resources