If, however, loblolly pine stands are burned in the fall (September or October), after the trees have undergone their last needle flush of the growing season but prior to the onset of dormancy, research indicates that 100 percent crown scorch is likely to kill them Slash pine appears to be more tolerant of severe crown scorch during the fall.
If more than 15 percent of a southern pine tree's needles are actually consumed by flames, the tree's chances of survival would be poor even if very little of the rest of the crown is scorched. Young vigorous trees are more likely to survive severe crown damage than are older individuals.
Magnitude and duration of growth responses in southern pines due to various levels and seasons of defoliation are not well documented. Both negative and positive responses have been observed, but the preponderance of evidence shows a direct relationship between diameter and height growth loss and crown scorch.
Providing no crown consumption took place, the above table will help in estimating potential growth loss in loblolly and slash pines over 3 inches dbh. These "ball park" estimates can be used for other southern pines as well, until more specific results become available.
A good indicator of hardwood control is a series of bark cracks extending into the cambium near ground level. This indicates sufficient heat was applied to penetrate the bark and kill the cambium. Although large hardwoods can be damaged by periodic fires they are difficult to kill.
Judge the success of burning for brownspot control by the number of longleaf seedlings with all infected needles burned off, but still having a protective sheath of green needles around the unharmed terminal bud.