Forest Health Spotlight: Brown Spot Needle Blight

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Landowners in North Carolina have planted a substantial number of longleaf pine seedlings over the last five years. In 2016 and 2018, record rainfall amounts and storms along with a decrease in the ability to conduct prescribed burning in these newly established longleaf stands may lead to an increase in brown spot needle blight.

longleaf pine seedling with brown spot disease

Longleaf pine with brown spot disease. Source: Robert L. Anderson, USDA Forest Service, Bugwood.org

Brown spot needle blight (Mycosphaeralla dearnessii, formerly Scirrhia acicola) can heavily infest longleaf pine seedlings in the grass stage and repeated defoliations can cause death. Bareroot seedlings and natural regeneration can be particularly at risk from this disease, more so than containerized seedlings, because they can stay in the grass stage longer. 

Close up view of brown spot needle blight

Lesions caused by brown spot needle blight
Source: wiki.bugwood.org

The life cycle of the disease on longleaf pine produces two types of spores, ascospores, and conidiospores. The ascospores are wind born and can spread long distances, while the conidiospores are spread through rain splashing. Longleaf in the grass stage can be especially vulnerable to conidiospores due to their needles being at ground level for several years.

The best method for control of the disease is prescribed fire in January or February. Longleaf pine seedlings with a root collar diameter of 3/4 to 1 inch in diameter should tolerate a low-intensity fire well. The fire will burn up the dead, diseased needles and eliminate the inoculum source for several years. Landowners should make sure that bud swell has not begun prior to burning.

Source:  US Forest Service, Forest Insect and Disease Leaflet 44