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.
The Southern Pine Beetle (SPB) is the most destructive pine bark beetle in the South. SPB infestations commonly originate in poorly managed or overstocked stands. Once underway, outbreaks can spread rapidly, killing trees over hundreds of acres, and move into managed stands.
SPB infestations can be identified in several ways. The most obvious symptom is the change of the needles in the tree crown from green to yellowish to reddish brown. Other symptoms are listed in Table 1.
Initial infestation is followed by the development of a "spot." The spot usually spreads in one direction as new trees are attacked in an area called the "active head" (see Figure 1). For more information on identification and life cycle of the SPB,, see Forestry Leaflet No. 5, Identification of the Southern Pine Beetle.
The risk of SPB infestations can be reduced by practicing
proper forest management. However, when infestations (spots) do occur, direct control
tactics are needed to minimize timber losses.
The cut-and-leave method is an effective means of
controlling small remote spots (10 to 50 infested trees) that cannot be salvaged. The
method involves felling infested trees and leaving them in the forest. The treatment
disrupts spot growth and disperses the emerging adult beetles. Spots should be treated
only if they contain freshly attacked trees.
When to Apply Cut-and-Leave
Cut-and-leave should be used during the period when SPB spots are expanding (approximately May to October). This method is most effective on spots of 10 to 50 active trees. Spots with fewer than 10 infested trees usually do not need to be treated. On the other hand, spots with more than 50 infested trees can be treated using cut-and-leave if the trees will eventually be salvaged. In every case, prompt treatment after detection is recommended.
Cut-and-leave is practical, relatively inexpensive, and requires a minimum of manpower and equipment. The treatment can be applied soon after spots are detected, even when salvage crews are not available or in areas not readily accessible to salvage equipment.
The main disadvantage is that a buffer strip of green, uninfested trees must be felled and left around each spot to assure that all newly attacked trees are included in the treatment. However, if salvage becomes feasible at a later date, all felled trees can be removed and utilized.
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.
Donald L. Ham, Extension Forester and Professor