Managing Piedmont Forests To Reduce Losses From the Littleleaf Disease – Southern Pine Beetle Complex

R.P. Belanger – Principal Silviculturist, USDA Forest Service, Southeastern Forest Experiment Station, Athens, GA,
R.L. Hedden – Forest Entomologist, Clemson University, Clemson, SC, and
F.H. Tainter – Forest Pathologist, Clemson University, Clemson, SC.

Integrated Pest Management Handbook, USDA, Forest Service, Agriculture Handbook No. 649, March 1986.

In 1980, the Forest Service and the Cooperative State Research Service of the U.S. Department of Agriculture initiated the Integrated Pest Management Research, Development, and Applications Program for Bark Beetles of Southern Pines. This research/applications effort concentrates on pine bark beetles and associated tree diseases in the South. This is one in a series of Integrated Pest Management handbooks.

Recognizing Symptoms

Foresters and landowners should first determine whether littleleaf disease and/or the SPB are already a problem on their lands. Symptoms associated with each of these pests can be easily identified in the field and indicate a need for evaluating the extent of the problems and making management decisions.

Littleleaf Disease Littleleaf disease rarely affects trees younger than 20 years of age and becomes increasingly severe in older trees. Symptoms of littleleaf (Fig. 3) are similar to those commonly associated with nutrient deficiencies. In initial stages, there is a slight yellowing of the needles with a tendency for needle elongation and shoot growth to be less than normal. The reduction in crown vigor is reflected by a decline in tree growth.

Figure 3 – The shortleaf pine in the center shows characteristic symptoms of littleleaf disease.

In later stages, crowns of trees have sparse and tufted foliage resulting from the annual reduction in needle and twig growth. Foliage of severely damaged trees is a yellow-green color especially visible during fall and winter. Stressed trees produce heavy cone crops consisting entirely of undersized cones with a high percentage of infertile seeds. At this point, tree growth has all but ceased.

The typical diseased tree dies within 6 years after initial symptoms become evident; however, some may survive for up to 15 years. Decline and mortality occur sooner for shortleaf pine than for loblolly pine.

Southern Pine Beetle The southern pine beetle attacks all species of pines, but prefers shortleaf and pitch pines in the Piedmont. Most forest landowners are familiar with the symptoms of SPB infestation (Thatcher and Connor 1985). The first obvious symptom of attack is a fading of the tree crown from green to yellow. In advanced stages of infestation (Fig. 4), crown foliage turns completely red or brown. On closer examination, popcorn-size lumps of pitch (pitch tubes) may be visible at tree heights up to 60 feet. Examination of the inner bark will disclose small S-shaped tunnels (egg galleries) made by SPB adults. These galleries are filled with a sawdust-like material (frass) left behind by the feeding adult beetles. This feeding girdles the pine. Blue-stain fungi, introduced by the beetle, penetrate into the sapwood and cut off the normal flow of moisture and nutrients through the tree. The combined effects of beetle feeding and fungal penetration lead to the death of the tree.

Figure 4 – Shortleaf pine killed by southern pine beetles.

Guideline are available to detect SPB spots (infestations) from the air and ground (Billings and Pase 1979; Billings and Doggett 1980; Billings and Ward 1984). Ground checks can also be used to determine whether stands are being damaged by littleleaf disease. Forest managers and landowners may not be familiar with the interactions of the two pests and methods of evaluating problem sites for the likelihood of littleleaf and/or SPB occurrence (risk), chance of SPB spot growth (hazard), and potential for timber loss. Yet, this information is important for selecting appropriate management strategies and practices for minimizing losses caused by both pests.

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