[Illustration: 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.