Using Prescribed Fire to Control Brown spot needle blight

Brown spot needle blight, caused by the fungus Scirrhia acicola, affects longleaf pine seedlings in the grass stage. Infected needles are mottled with various colored small spots that turn brown with time. The infected needles eventually die, defoliating the seedling. Raindrops spread spores released from fruiting bodies on the needles short distances throughout the year. During the winter and early spring, additional spores are produced from perithecia and these spores can be dispersed longer distances by winds. The disease will prevent longleaf pine seedlings from growing out of the grass stage and can cause death with repeated defoliations.

Control of brown spot needle blight by prescribed burning has been documented since the 1930s (Siggers 1932) and is still the most practical way to rid a stand of the disease today (USDA Forest Service 1989). Fire should only be used when infection exceeds tolerable levels. Maple (1975) reported that burning should be conducted when 20% of the stand is infected. Ideally, seedlings should have a minimum root collar diameter of 0.4 inches in the grass stage before burning (Phelps et al. 1978).

The prescribed burn should be a fast moving head fire during the dormant season that consumes the infected needles but not the terminal bud in order to rid an infected stand of the disease. May fires are more beneficial than March burns because of better seedling survival and height growth after the burn (Grelen 1983). Greater longleaf seedling height and needle blight reduction was also reported with May burns on a sandy site in Alabama (Maple 1977).

Prescribed burning reduces brown spot needle blight in a stand by destroying the infected needles, thus reducing inoculum. Burning may also be done before seedling establishment in order to sanitize areas that have shown high levels of infection. In addition to reducing disease pressure, these fires may also help to release seedlings from the grass stage.