Mechanical Control of Southern Pine Beetle InfestationsThis article is part of a larger document. View the larger document here.
Periodic outbreaks of the southern pine beetle (SPB) may affect thousands of acres of commercial pine forests in the Southeastern United States, Mexico, and Central America. Accordingly, this species is the target of more aggressive and effective suppression programs than any other bark beetle pest in the world. The strategy for controlling the southern pine beetle during periodic outbreaks has changed in recent decades. Attempts to eradicate beetle populations by treating all infested trees with insecticides, the strategy prior to 1970, has been replaced with mechanical control tactics as a means to reduce resource losses. Once multiple-tree SPB infestations (spots) become established and exceed a certain size threshold (about 30 infested trees), they may rapidly expand and persist for multiple beetle generations, until lack of hosts, cold temperatures, direct control, or other factors intervene. The current strategy for suppression relies on identifying those SPB spots capable of rapid and prolonged expansion and treating these with mechanical control tactics to prevent loss of additional trees. Principal tactics are cut-and-remove (salvage removal) and cut-and-leave. A third tactic, pile-and-burn, is available but seldom used. Both cut-and-remove and cutand- leave involve felling all brood trees plus a buffer of adjacent uninfested trees to disrupt further spot growth, the primary means of host tree colonization and beetle survival during summer months. In the case of cut-and-remove, felled trees are removed from the site and sold to a mill, further reducing the landowner’s economic losses. The cut-and-leave tactic involves felling targeted trees (those containing SPB brood, fresh attacks, and adjacent buffer trees) toward the center of the infestation and leaving them onsite. Most spot disruption tactics are applied during the summer months when beetles are least capable of dispersing long distances or initiating large infestations. These tactics have proven effective in reducing tree losses up to 85 percent. Some mortality of SPB broods may occur in trees felled in cut-and-leave treatments, but this effect is not consistently achieved nor required for treatment success. Direct control, however, is just one option for effective management of SPB. A comprehensive pest management system also requires monitoring, prediction, early detection, and evaluation of infestations, as well as preventing beetle problems through silvicultural treatments of beetleprone pine stands (discussed in other chapters of the Southern Pine Beetle II). This chapter discusses the rationale, methods of application, and effectiveness of mechanical control treatments (cut-and-remove, cut-and-leave, and pile-andburn) for addressing SPB outbreaks.