Infection of needles occurs throughout the summer when ever temperatures are 68-77 F and moisture is available. Severe infection by Mycosphaerella dearnessii results in the lesions coalescing together which causes the entire needle to turn brown and fall off the seedling. The infected needle serves as a inoculum source for future infections if conditions are favorable. Repeated infection by Mycosphaerella dearnessii eventually results in the complete defoliation of the seedling. The reduction in leaf area causes a reduction in growth and an increase in the amount of time the seedling remains in the grass stage, or mortality of the seedling.
Smaller seedlings die sooner than larger seedlings.
In natural regeneration settings, brown spot needle blight can be useful to reduce stocking levels naturally. However, in artificial regeneration, considerable amounts of time and money have been invested into the stand to allow brown spot needle blight to reduce stocking levels or increase rotation age. Periodic controlled burns conducted a year after establishment, and every three years later, in the winter is an excellent method to reduce the levels of inoculum that cause infection. Longleaf pine has a large bud which is protected and can tolerate periodic burnings. The use of resistant seed from tree improvement programs is recommended if available.