Pine trees grow across the United States in residential and commercial landscapes, recreational areas and timberlands. They typically remain free of disease if planted in the right location and maintained properly. Pine tree species vary by region and growing conditions, as do the diseases that can afflict them. Diseases on pine trees include galls, cankers and needle blights. Some diseases are not severe enough to need treatment, whereas others respond to fungicide.
Pine Needle Diseases
Several diseases affect the needles on pine trees. Brown Spot disease begins as small spots on the infected needles. The brown areas spread around the needles, the tips of the needles turn brown, and the needles drop off in the fall. The symptoms of Littleleaf Disease include small yellowish-green needles and thin growth in the crown of infected pine trees. Littleleaf Disease usually affects a group of trees, all of which gradually decline and die. Two kinds of needleblights are common on pine trees. One type causes chlorotic spots on the infected needles during the fall or winter. The spots spread, turn red or brown, girdle and kill the needles. The resulting defoliation can be severe.
A second type of Needleblight affects the older needles. Long narrow black fruiting bodies grow on the lower surface of the infected needles, which causes the needles to die back and drop.
Two kinds of Needlecast can cause pine trees to lose their foliage prematurely. One type of Needlecast affects the current season's needles, which develop yellow spots, turn brown in spring or late fall, and drop. The disease also causes twig dieback.
Another type of Needlecast causes the previous year's needles on the lower branches to turn brown and drop.
Pine Gall Rusts
Fungi cause rust diseases, forming blisters filled with orange or yellowish-orange spores on pine trees. When the spores release, they typically infect alternate host plants, rather than other pine trees. Pine-Pine Gall Rust, also called Western Gall Rust, is one that infects other pine trees. Red oak trees are the alternate host plants for Pine-Oak Gall Rust, which is also known as Eastern Gall Rust. The spores of Pine Needle Rust infect nearby aster and goldenrod plants, while species of the Ribes family, such as currants and gooseberries, are the alternate host plants for White Pine Blister Rust.
Other Pine Diseases
New growth on pine trees affected with shoot blight turns brown, appears soaked with resin and dies. The disease can continue into and kill the main stem.
Pitch cankers are slightly sunken areas of dead bark on the branches or trunks of pine trees. They ooze a large amount of pitch, and the underlying wood and surrounding bark are soaked with pitch. Branches with pitch cankers die, and trees with pitch cankers on the trunk can also die. Symptoms of root or butt rot on pine trees include thin foliage, red needles on dead trees and basidocarps (mushrooms) at the soil level of infected pine trees. Trees with root or butt rot typically grow in a circle around the stump of the infected pine tree.