Eastern gall rust, caused by the fungus _Cronartium cerebrum_, attacks
many species of eastern hard pines. The disease ranges eastward from the
Great Plains and is most severe in the South on Virginia and shortleaf
pines. Like most rusts this fungus requires an alternate host in
addition to its pine host. In this case oaks, especially the red oak
group (black, red, scarlet and pin) are the alternate hosts. Damage to
the oaks is generally not of economic importance as only the leaves are
affected.
[Illustration: Fruiting gall showing red-orange spores on Virginia
pine.]
On pines the fungus causes the formation of globose to sub-globose
galls. Canker formation occurs occasionally but mortality generally
results from wind breakage at the gall rather than by canker formation
as literally hundreds of galls may appear on a single tree. They are not
lethal to the tree, but may ruin tree form and on a large stem they can
lead to an open decayed wound, as decay fungi are often secondary
invaders of rust infections. The shape of galls and the arrangement of
the spore sacs filled with red-orange spores present a cerebroid
(brain-like) appearance. During the spring the bright orange galls are
very striking.
This disease is sometimes a problem in nurseries where seedlings are
attacked and killed. This is where control efforts are concentrated.
Fungicide protectants are applied to the seedling foliage to prevent
infection from spores produced on oaks. Contact your local forestry
extension agent or the nearest Division of Forest Pest Management for
the latest recommendations. Under forest conditions, control is not
economically feasible. Trees of poor form should be removed during
thinning operations.