Ponderosa pine trees are a staple in Arizona. With the Coconino forest being the largest stand of ponderosa pine in the world, any native Arizona can easily recognize the ponderosa Pine tree. However, if you are lucky enough to own a ponderosa pine, you will want to read this to ensure it isn't suffering from a disease known as red-band needle blight. A condition that is common among pine trees and will eventually kill them if left untreated.
These are the types of pine that are most affected by this condition:
Mugo pines are highly susceptible
Scotch and red pines are generally resistant
Red-band needle blight (Dothistroma needle blight) gets its name because of its most common and noticeable symptom. Initially, symptoms include dark green bands on the needles; these get quickly replaced with brown or reddish-brown lesions. It's these reddish-brown legions that make up the "Red Band." After that, only the base of the needle will stay green, with the rest changing to tan or brown. Eventually, tiny, dark brown or black fruiting bodies are produced and release spores. The fruiting bodies are visible in the diseased area with a needle lens. A flap of needle epidermis typically covers them.
Infection of current and second-year needles is usually in the lower crown of sapling-size trees. Seedlings and large trees are rarely infected. Newly infected needles have green bands that turn red or brown in late summer. These needles die from the tips back. Infected second and older-year needles can be cast the same year they become infected. Infected needles may develop extensive browning 2-3 weeks after the first appearance of symptoms and drop rather than remain on the tree for their standard two to three years. For example, infected second-year needles are often cast (dropped) before the infected current-year (first-year) needles. Needles that become infected the year they emerge are often not shed until late summer the following year. Repeated severe infections over several years will result in decreased vigor and growth of the tree, ultimately causing death.
Disease Life Cycle:
The Red band blight reproduces by forming small, black fruit bodies on the needles, usually seen within the red bands. Spores release from these, and if they land on a susceptible host, they germinate on the needle surface and grow through the stomata (tiny pores used to "sweat" water through the needles"). Late spring to late summer is the most critical period for infection; the area is often the wettest from the spring rain and snow runoff. Germination requires moisture, and successful establishment occurs at temperatures between 53 and 64 degrees Fahrenheit under high humidity conditions. Once this spore release is over, the tree sheds the needles.
How to help my tree:
Of course, the best way to help your tree against red band needle blight is to prevent it in the first place. You can routinely do a few things to ensure your tree is safe. First, control the weeds and lower growth around the tree. You will also want to remove the lowest whorls of branches; this will increase the airflow around the tree's base and help prevent moist conditions where the disease can grow. While enjoying your yard and trees, pay close attention to the color of the needles to ensure none are turning yellow when they should not. Something to note: you should not shear your trees in wet weather; this will increase the chances of any existing disease spreading. If there are diseased areas, prune the healthy areas first and wash your tools between each cut.
If you think your tree might have red band needle blight, you must call an arborist. An arborist can diagnose the tree and make a plan that will save it. In the meantime, prune away the lowest affected branches to help with air circulation in the lower part of the tree. Make sure you clean your tools before and after you prune the tree and between cuts. A simple solution with alcohol will work best to sterilize your tools. The arborist will know how to help the tree from there. He will need to remove any parts of the tree that have been affected. He may also want to boost the tree by enhancing the soil with nutrients the tree can use to fight off any new infection.
If you own a ponderosa pine, routine maintenance and checkups are a small price for its beauty and fragrance. Have an arborist inspect your yard at least twice a year to protect your trees from red-band needle blight.