CONSERVATION CORNER
December 11, 2006
Insects and Diseases of Southern Pines
by James L. Cummins

As I drive around Mississippi, dead pines after this summer's drought are more common than not. These deaths are due primarily to insects.

Both insects and pathological agents can have negative impacts on all southern pines. This is especially true after Hurricane Katrina. However, as a general rule, longleaf pine is more resistant than other pine species. For instance, although pine tip moths cause serious damage to loblolly and slash pine, they do not affect longleaf pine. Southern pine beetles can attack longleaf, but this usually occurs only when the beetle populations are epidemic in size. Engraver beetles and black turpentine beetles will also attack longleaf, but are usually a problem only when trees are under severe stress from lightning strikes, excessive logging damage or extreme fire damage. Control of logging damage and removal of lightning stuck trees are the best methods for the prevention of beetle infestations.

According to Randy Browning, a Field Biologist with Wildlife Mississippi and the U.S. Fish and Wildlife Service, "Several pathogens that affect all southern pines include annosus root rot, fusiform rust and pitch canker. Although longleaf pine can be infected with these pathogens, they are less susceptible to these diseases than loblolly or slash. However, brown-spot needle blight is a serious disease of longleaf and can suppress growth and cause eventual mortality in grass-stage seedlings. Brown-spot is a fungal infestation that causes needle loss in grass-stage seedlings. However, brown-spot is not a significant problem once active height growth begins. Since grass-stage seedlings of longleaf pine are very tolerant to fire once they have reached a ground line diameter of 0.3 inches; brown-spot needle blight can be controlled with prescribed burns. Controlled burns conducted during the dormant season kills the fungal spores and removes infected needle tissue. Prescribed burns also reduce competition, thus promoting active height growth in longleaf seedlings. However, burns should be conducted before the majority of the seedlings begin active height growth. Remember, longleaf out of the grass-stage and less than 3 feet in height are very susceptible to fire."

Browning states that brown-spot needle infestations are worse when longleaf seedlings are grown in the open with minimal ground cover. However, seedlings regenerated naturally under moderately dense overstories are protected from serious infestations. Because of this, the shelterwood is a practical method of natural regeneration for longleaf pine. The parent trees should be harvested by the time the seedlings reach 2 years of age.

Brown-spot needle blight can also be suppressed in nurseries with applications of fungicide. Seedlings can be sprayed with a mixture of 4 pounds copper sulfate, 4 pounds hydrated lime, and 50 gallons of water at a rate of 60 gallons per acre. Fungicide application is a viable alternative, especially in situations where fire is not practical.

When longleaf pine is regenerated, make sure seedlings are free of brown-spot. The best method for long range control of brown-spot needle blight is by planting resistant seedlings.