Fusiform rust of southern pines is considered the single most important disease of conifers, occurring both in the field and in the nursery. It results in millions of dollars of damage each year in the southern United States. The primary hosts of fusiform rust are young loblolly and slash pines. Generally, the trees are resistant by the time they are 15 years old. Several species of oak serve as the alternate host for this fungus.
Red oaks are notably more susceptible to infection than white oaks.
Symptoms of fusiform rust include a large fusiform-shaped gall on the trunk or branches of the tree, as shown in Figs. 1 and 2. Also, newly infected needles become necrotic. Although trees often continue their growth after infection, mortality of the tree may eventually result. A sign of the disease is shown in Figs.