04/19/95 - Southern Pine Beetle Outbreaks in Northern Florida

John L. Foltz (retired)
University of Florida, IFAS
Department of Entomology & Nematology
Gainesville, FL 32611-0620

Outbreaks of the southern pine beetle (SPB), Dendroctonus frontalis, the most aggressive and destructive of five bark beetles species infesting southern pines, are now present across northern Florida. As of April 15, 1995, outbreak populations existed in Alachua, Baker, Bradford, Columbia, Gadsden, Leon, Nassau, Okaloosa and Union counties. Citizens throughout northern Florida should carefully monitor all pines infested by bark beetles and be prepared to initiate community-wide suppression programs if the SPB is detected.

Biology and Behavior. The adult SPB is a reddish-brown to black cylindrical beetle about 3 mm long, smaller than a grain of rice. Females initiate the attacks on trees and emit a pheromone that attracts males and additional females. Within a few days thousands of beetles colonize the tree and overwhelm its defenses. Excess beetles often land on and colonize nearby trees. Females tunnel through the inner bark, periodically constructing a niche and laying an egg. Males follow the females and close the gallery behind them with boring dust. After about a week of egg laying, parent beetles emerge to infest additional trees. Larvae feed on inner bark for about two weeks, then pupate in the outer bark. New adults begin emerging just four weeks after initial attack, about the same time the tree crown is turning from yellow-green to red. These beetles may fly 1 or 2 miles before attacking a new tree.

Detection and Identification. SPB infestations usually occur in spots that gradually enlarge with time. Red-crowned pines and surrounding green trees should be examined for signs of infestation. Popcorn-like pitch tubes, boring dust, and numerous holes through the bark are signs of bark beetle infestation. A southern pine beetle infestation is identified by the winding and overlapping galleries constructed under the bark by females as they lay eggs. The egg galleries of the three Ips beetles, in contrast, are I-, Y-, or H-shaped with two to four relatively straight galleries radiating out from the "nuptial chamber" constructed by male beetles. The black turpentine beetle infests around the base of the tree and makes only a short, mostly vertical gallery before laying a large clutch of eggs. All five species often occur on the same infested tree, so a tree should be examined at several heights on the trunk to avoid overlooking an SPB infestation.

Control. Because of the dispersal and aggregation abilities of this insect, it is important that all infested trees over a large area be treated. If possible, remove newly infested trees and destroy or treat the infested bark before beetles mature and emerge to attack surrounding trees. Once beetles have emerged from a tree, removal is unnecessary except to protect life and property from falling branches and stems.

Prevention. Infestations often start on stressed and injured trees in older-aged dense stands, so cultural practices that promote healthy trees will reduce the frequency and severity of infestations. During outbreaks, avoid pruning and other activities which produce terpenes that attract these beetles. If nearby trees are infested, homeowners may wish to have a pest control service apply a insecticide (labeled for pine beetle control) to their uninfested trees. The insecticide should be applied on dry bark, to the point of runoff, from at least the base of the crown down to the ground line. If Ips beetles are abundant and aggressive, then the upper stem and larger branches should also be treated. When carefully and properly applied, these insecticides dry in a few hours and pose little danger to birds, squirrels, and humans.

Biology of the Southern Pine Beetle

The UF/IFAS Pest Alert WWW site is at: http://entomology.ifas.ufl.edu/pestalert/