Southern Pine Beetle
The southern pine beetle (Dendroctonus frontalis Zimmerman) is one of the most widespread and destructive pine insect pests. Loblolly, shortleaf, pitch, pond, and Virginia pines are the favored host tree species. Tennessee’s southern pine beetle population gradually began to build in 1998 and killed approximately 350,000 acres and $358 million of pine in the succeeding years. This mass epidemic drove pine prices down as markets were flooded with salvaged pine sawtimber and pulpwood.
The adult southern pine beetle is dark red-brown and roughly the size of a grain of rice. The beetle undergoes four stages in a lifecycle: egg, larva, pupa, and adult. Adult females bore through the bark of the tree and begin constructing S- shaped egg galleries in the cambium and males follow, packing the tunnels with frass. The newly hatched larvae mine away from the galleries and travel towards the outer bark to feed and pupate. New adults then exit the tree through small, round holes in the bark and fly to attack new trees. Beetles also infect the tree with bluestain fungi which damages the sapwood. This fungus, coupled with the construction of the galleries girdles the tree and leads to eventual tree mortality.
Symptoms of southern pine beetle attack include the presence of pitch tubes along the trunk (resembles popcorn); the tree crown begins to fade, turn red or needles fall off; the presence of small round exit holes in the bark, which will be very loose and peel off.
Since 2003, southern pine beetle populations have declined as availability of host species is low and populations of predator clerids are high. The pine sawtimber and pulpwood markets have not fully recovered from the early 2000’s infestation but have been slightly improving. Regionally, only a handful of states are seeing spotty southern pine beetle infestations which can be easily managed.
Four Tennessee counties are surveyed annually using pheromone baited traps. The samples collected from these traps are analyzed and the resulting data is entered into a monitoring portal which is shared by a number of states across the pine region. This collaborative effort helps managers and researchers track southern pine beetle movement and assess future risk.
The southern pine beetle is very attracted to stands of pine that are stressed in some way. Drought and overcrowding are the two most common stressors of tree health. Proper forest management and timely thinnings or harvests are the best management options to protect pine stands against the southern pine beetle. If an infestation does occur in your pine stand, options for management include cut & remove, cut & leave, cut & hand spray, pile & burn , or aerial pesticide applications.
What Can You Do?
If you own a single pine or a stand of pine, the best thing you can do is keep the pines healthy. Correct plant spacing, timely thinnings, and clean harvesting can prevent southern pine beetle populations from building. Learn to recognize what the signs and symptoms are of an infestation and immediately contact your county agent, professional forester, or Nathan Hoover with the Division of Forestry. Early detection is very important to preventing major infestations.
Science & U! (Docu-news video featuring southern pine beetle migration north to New Jersey.)