Southern Pine Beetle
Forest insect and disease pests cause an estimated growth loss and mortality in excess of $8 million each year in South Carolina forests. An integrated pest management (IPM) approach on your forest lands could significantly minimize your potential losses.
All pine species can be attacked, but some are more susceptible than others. In the Piedmont, shortleaf pine is more susceptible than loblolly or Virginia pines, and in the Coastal Plain loblolly is more susceptible than longleaf or slash pines. Ordinarily, unhealthy, weakened pines are the most susceptible to beetle attack, but as the beetle population increases, even healthy, fast-growing pines will be attacked.
LIFE CYCLE STAGES
The southern pine beetle may have up to eight generations a year with four life stages during each generation: egg, larva, pupa and adult. Development of all stages continues throughout the year, slowing considerably in the winter and accelerating in the spring and summer. One life cycle or generation from egg to adult may take from 26 to 54 days depending on the season. Over a temperature range of approximately 60 to 85 degrees F, the length of time for each stage varies as indicated below . Adults reach an ultimate length of only 1/8 of an inch, similar in size to a grain of rice.
Reemergence - Attacking adults begin to reemerge one to three days after the mass attack, mating and egg laying, and continue to do so for 10 to 14 days. Reemerged adults may attack additional pines and contribute to infestation growth.
Brood Development - Small C-shaped larvae hatch from the eggs and feed in the cambium and then in the inner bark. Near the end of the larval stage, the larvae move into the outer bark and pupate. The pupae develop into immature yellowish-white (callow) adults about one week before becoming dark in color. Upon full development, the adult constructs an exit or emergence hole through the outer bark.
New Adult Emergence - Emergence is temperature related, and the adults may remain under the bark for a period of time if conditions are not favorable. Usually colder air temperatures delay emergence. In addition, emergence does not take place all at once. A few beetles leave the tree initially, followed by a larger number, and then a declining number over an extended period of time.
The dispersal of emerging adult beetles is also affected by environmental conditions. During the winter, emerging beetles may not disperse, but reattack the same tree instead. Usually, however, emerged adult beetles leave the host tree and, depending on the time of year, either aggregate on adjacent trees under attack or fly off to find a suitable new host tree elsewhere.
Keeping your pine timber stands healthy and vigorous, and having a good knowledge of the southern pine beetle habits and symptoms is essential to effectively deal with this destructive pest. Professional advice and assistance is available through the South Carolina Forestry Commission, Clemson University Cooperative Extension Service, U.S.D.A. Forest Service, forest industry personnel, and private consulting foresters. Acknowledgement: USDA Agriculture Handbook No. 575
Donald L. Ham, Extension Forester and Professor