Small bug can equal big problems
Dendroctonus frontalis, more commonly known as the southern pine beetle, is the most destructive forest insect pest in the South. Its range covers the United States from Pennsylvania to Texas, including the entire southeastern portion of the country and from Arizona and New Mexico through Mexico to Nicaragua.
In the southeastern United States, loblolly, shortleaf, pitch, pond and Virginia pines are the favored hosts. However, during major outbreaks, the southern pine beetle may infest all pine species, and even related hosts, such as spruce and hemlock.
There are six species of pine native to Mississippi – loblolly, longleaf, shortleaf, slash, Virginia and spruce- with loblolly and shortleaf pines being the favored hosts.
The southern pine beetle is typically in outbreak status every year within its range. The average annual tree mortality rate in the United States exceeds 100 million board feet of sawtimber and 30 million cubic feet of pulpwood.
“Weakening of trees by flooding, windstorms and drought typically precedes outbreaks,” said Russell Bozeman, Mississippi Forestry Commission (MFC) state forester. “The first indication of attack is usually the yellowing or browning of needles, followed by the formation of white, yellow or reddish-brown pitch tubes.”
Female southern pine beetles initiate the attack on suitable hosts. The initial female will attract a male, which in turn attracts more beetles. If enough beetles are attracted to the host tree, tree resistance is overcome and the tree is successfully colonized.
Initial attacks are in the mid-trunk and then the length of the tree. Adult beetles bore through the bark and excavate long winding “S” shaped galleries. Eggs are laid in niches along the galleries. Larvae feed in the cambium until grown, and then excavate cells near the bark surface in which to pupate. After pupation, adult beetles chew through the bark and emerge. The complete cycle of the attack takes from 25 to 40 days, depending on the temperature.
Additionally, beetles will inject pines with blue stain fungi, which blocks the water conducting tissue of the tree and contributes to rapid tree death.
“According to the U.S. Forest Service, the southern pine beetle is the most destructive forest insect pest in the south,” Bozeman said. “Because of its destructive nature and the amount of pine forest in the state, the MFC spends valuable time and resources on detecting and preventing infestations before they reach outbreak status on private and state-owned lands.”
Twice a year, the MFC conducts forest health flights to monitor forest health issues across the state, including southern pine beetle populations. The MFC uses this data, along with data from the U.S. Forest Service, to populate an interactive map with suspected southern pine beetle spots.
“We encourage landowners to be proactive with their forest management,” said Bozeman. “The most effective method of managing southern pine beetles, according to the U.S. Forest Service, is through preventing outbreak populations and creating forest conditions that lessen impacts once outbreak occurs.”
One of the best strategies landowners can use is proper thinning to attain desired forest densities. Thinning reduces the likelihood that expanding infestations will become established by increasing tree vigor and changing the forest’s microenvironment.
“The MFC has a Southern Pine Beetle Prevention Program that provides cost-share funds to encourage private landowners to thin their dense pine stand before an outbreak occurs,” Bozeman said. “Past experience tells us that healthy stands of timber that have been properly thinned and managed are less susceptible to southern pine beetle damage.”
The Southern Pine Beetle Prevention Program is currently only available in the 33 counties most susceptible to outbreak.
For more information about the southern pine beetle, visit https://www.mfc.ms.gov/ or like and follow @MSForestryComm on Facebook and Twitter.