Plant Pathology Infobytes
April 1, 1997
What's That Orange Stuff On My Pine Tree?
The appearance of masses of orange growth on swollen areas along branches and trunks of loblolly and slash pines at this time of year always raises concern among homeowners. "What's happening to my pine tree, and is it going to die?" is a common question received by County Extension Offices when this disease first shows up.
Technically this condition is referred to as fusiform gall rust. Loblolly and slash pines are most susceptible to this fungus disease, while longleaf and shortleaf pines are resistant.
Each year in late March and early April, the surface of galls is covered with an orange growth (literally millions of fungus spores), which is a stage in the life cycle of the fusiform gall rust fungus.
Back to the question raised by homeowners about whether fusiform gall rust will kill affected pine trees. If the galled area appears on the main trunk of the tree, the answer is "yes." Tree death may not occur for a period of several years, but eventually the fungus destroys so much woody tissue of the trunk that death becomes inevitable. There are no fungicides or other types of treatment which may be used to cure gall rust infected pine trees.
Attempting to cut-out galled areas by pruning doesn't work, since by the time the gall is apparent, the fungus has extensively invaded trunk tissues, so that pruning only removes a small part of the infection.
In most cases, however, a fusiform gall rust infected tree is blown over during windstorms before the disease has a chance to cause death, since the wood formed within galled areas is highly subject to breakage. Insects frequently invade galled areas and cause further deterioration and increased susceptibility to wind breakage.
It's best to consider removal of trunk-infected trees, particularly if trees are located next to dwellings, parking areas, or any spot where a fallen tree would create serious problems.
Removal of galls is an option provided the infected area is on a branch and the gall is one to two feet away from the main trunk. There's a good chance that the rust fungus hasn't grown back into the main trunk in such cases. Thus, removal of galled branches may allow you to salvage the tree. Left unpruned, the fungus will eventually invade the trunk area where pruning recourse is not possible.
For additional information on diseases and other pests of trees and landscape plants, check with us at your county Extension office.
Infobytes newsletter was written by the late Dr. Frank Killebrew, Extension Specialist.