Introduction
Forest managers and pest control specialists have long needed a reliable and practical early warning system to detect developing outbreaks of the southern pine beetle (SPB), Dendroctonus frontalis (Coleoptera: Curculionidae: Scolytinae), the most destructive forest pest of southern pine forests (Thatcher and others 1980). Because aerial surveys to detect SPB infestations do not become effective until late spring or summer (Billings and Doggett 1980), a more efficient system for monitoring SPB populations early in the season has value. Early detection of pending outbreaks gives forest pest managers valuable insight for scheduling detection flights and planning suppression programs.
In 1986, the Texas Forest Service began development of an operational system using pheromone-baited traps for predicting SPB infestation trends (increasing, static, declining) and population levels (high, moderate, low). In cooperation with State and Federal pest management specialists, the system was implemented throughout the South beginning in 1987 (Billings 1988, 1997). Validation and refinement of the system have been conducted periodically with use of year-end SPB infestation detection records. Here, we evaluate the accuracy of this prediction system, based on results from 16 States, most of which have now deployed the system for 20 consecutive years (1987-2006).
The southern pine beetle’s range extends from New Jersey to Florida and west to Texas, coinciding with the distribution of its major hosts, loblolly (Pinus taeda) and shortleaf pine (P. echinata). SPB populations also are found from southern Arizona south to Nicaragua. Outbreaks of this insect tend to occur somewhere within its range every year, with peak populations occurring every 6 to 9 years in many Southern States (Price and others 1998). The location and intensity of SPB outbreaks may vary greatly from year to year. Unlike most other destructive bark beetles of the genus Dendroctonus, SPB completes up to seven generations per year in Gulf Coastal States and infests host trees in distinct and predictable patterns that vary with the seasons. For example, most new multiple-tree SPB infestations (spots) are initiated during the spring, following long-range dispersal of overwintering beetle populations (Hedden and Billings 1979, Thatcher and Pickard 1964). In the late spring and summer, adult beetles tend to attack host trees on the periphery of the same spots from which they emerged (Gara 1967; Hedden and Billings 1977, 1979; Thatcher and Pickard 1964). This behavior leads to expansion of previously established spots, rather than the initiation of new ones. These expanding infestations (see the figure to the right) are easily recognized in summer detection flights by the presence of pines in various phases of crown discoloration (Billings and Doggett 1980). Emerging SPB adults tend to disperse again in the fall, redistributing the population among scattered single trees, nonexpanding spots, and established infestations prior to winter.
Encyclopedia ID: p3290
