Fruiting bodies of pine needle rust on loblolly pine.
Nearly all the native pines in southern United States are attacked by various needle rust fungi of the genus Coleosporium. This disease is very common, but causes little harm to the trees. Many species of this rust also attack broadleaved weeds in addition to the pines, needing both host types to complete their life cycle.
Needle rusts are most prevalent on young trees in the seedling to sapling stage. In the spring or early summer small, delicate white fungus “cups” filled with yellow to orange spores are produced on the needles. From a distance entire seedlings may appear to have a whitish or yellowish cast. Individual needles which are heavily infected may die, turn brown, and drop from the tree. However, the entire tree is rarely defoliated. Small red “rust pustules” form on the undersurface of the weed leaves. These are replaced by dark structures later in the summer.
The needle rusts are not important enough to warrant control in natural forests or plantations. If the weed (alternate) host is known, it can be eradicated around nurseries of susceptible pine species. However, it would be better to establish nurseries in rust free areas.
CEDAR APPLE RUST
Cedar apple rust, caused by Gymnosporangium juniperi-virginianae, is important commercially in the apple-growing regions of the Virginias, Carolinas, and the Mississippi Valley. The alternate hosts of this rust are eastern red cedar and several species of junipers.
Fruiting galls containing spores on cedar tree.
