Fusiform rust, Cronartium quercuum f. sp. fusiforme, is the most damaging disease of slash and loblolly pines throughout the southeastern United States. This disease causes stem, branch and trunk cankers (galls) to form on infected trees (Figures 46 and 47). The majority of infections occur prior to age 5. In the early spring active galls produce yellow-orange spores (aeciospores) that are windblown to young, tender oak leaves (Figure 48). Water, willow, and laurel oaks are the most susceptible species affected. The fungus goes through three additional spore stages underneath the oak leaves. The fourth and final stage results in basidiospores being formed. The basidiospores are windblown to new pine needles and/or succulent green bark areas of young trees thus completing the disease life cycle.

The amount of infection in planted and natural pine stands varies considerably across the South (Figure 49). Factors such as individual tree resistance, site characteristics and rust virulence all interact to influence infection levels.

When regenerating sites to pine, land managers must take steps to deal with fusiform rust. Below are some practices that will help minimize rust problems and protect economic investments.

Artificial Regeneration

Use rust resistant seedlings (improved) that are available from state and privately owned nurseries. These seedlings are the result of many years valuable research that hopefully will result in increased seedling resistance to the disease. Further protection from rust is provided by timed applications of fungicides to these seedlings at the nursery. However, sometimes these fungicides do not get applied for one reason or another. Occasionally seedlings will leave the nursery that are rust infected. Seedlings should be inspected for obvious stem swellings and culled prior to planting (Figure 50). Infected seedlings should be reported to the appropriate nursery officials immediately. Don't wait.

In high hazard regions (Figure 49) increase planting densities to allow for anticipated losses. This will, of course, increase the number of thinnings required throughout the life of the stand.

Consider site preparation techniques that reduce oak trees unless they conflict with other management objectives (prescribed burning, herbicides, and intensive mechanical preparation). It has been suggested by various pathologists that windrows containing large amounts of oak stumps and debris may provide ample oak sprouts that will later serve as alternate host material for future rust infections.

Use seed from a resistant source. Seed should be treated with an approved bird and rodent repellent (see appendix).