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Pine Bark Beetles

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Friday, March 8, 2019 - 7:00am

Announcer: Farm and Family is a production of the Mississippi State University Extension Service.

Amy Myers:  Today we're talking about pine bark beetles. Hello, I'm Amy Taylor, and welcome to Farm and Family. Today we're speaking with John Kushla, Mississippi State University Extension Service Forestry Specialist.

John, what are pine bark beetles?

John Kushla: These beetles bore through the bark of our pines and feed on the tissue beneath. There are five different species that attack our Southern pines. These include the southern pine beetle, there are three species of engraver or Ips beetles, and the black turpentine beetle. Most of these insects are smaller than a grain of rice.

Amy Myers: Okay, so are bark beetles very damaging to our trees?

John Kushla: Yes and no. Most of the bark beetles will kill a few trees in a stand. However, the southern pine beetle, Dendroctonus frontalis, is very harmful. It is considered the most damaging forest pest in the Southern United States, Mexico, and Central America. In the U.S. alone, it's probably killed a billion dollars worth of timber since 1960.

Amy Myers: Which pine species are most susceptible to this?

John Kushla: Most of our two and three-needle pines in the Southern United States, which include loblolly and shortleaf pines in the Southeast and Ponderosa pine in the Western United States. Our longleaf pine and slash pines are more resistant.

Amy Myers: What makes our pine trees vulnerable?

John Kushla: Stressed trees actually smell different to the beetle, and that's how they can hone in their attack. Also lightning-struck trees where resin flow is interrupted for a couple of weeks, drought conditions, and overly dense stands, that is trying to grow too many trees on a given acre of land. It takes thousands of beetles to attack and kill a stressed tree, but they can do it in a matter of days.

Amy Myers: How exactly do bark beetles kill a pine tree?

John Kushla: It's a one-two punch. When the adults bore through and lay their eggs under the bark, the larvae feed on the phloem tissue. This is transporting sugars downwards to the roots, and their activity effectively girdles the tree. The beetles often carry a blue stain fungus which doesn't affect the beetles, but the fungus, once it gets into the tree, will block the xylem tissue, which transports water upward from the roots, and so you get this one-two effect.

Amy Myers: And what are the signs of infestation?

John Kushla: Stage one, you get the appearance of what we call popcorn on trees, which is sap oozing from the bore holes trying to force the beetles out. Attacking females will produce a pheromone which attracts other beetles. Stage two are where the galleries are laid for the eggs, and these are made beneath the bark in what we call brood trees, and as these beetles feed, these trees fade in color from green to yellow. Stage three, you're going to see emergence holes which appear like shotgun holes through the bark, and the tree is going to be red-topped or completely bare of needles.

Most spots are generally less than an acre and do not become self-sustaining. The southern pine beetle is unique among bark beetles because its spots can grow in size, and if the populations become high enough, the beetles can attack healthy trees.

Amy Myers: Now what can be done to protect pine forests from this?

John Kushla: Thinning is the best preventive action against all of our bark beetles. More light, nutrients, and water for the remaining trees makes them more healthy. Also the greater air movement through a thin stand will disrupt the pheromones that the beetles are using to coordinate their attack. The increased distance between trees also lessens the chance of a new attack.

Active southern pine beetle spots are controlled by cutting. If they're large enough, you can salvage them. You want to fell your Stage one and two trees toward the spot center and leave your Stage three trees standing for predators to inhabit that can eat the beetles. We also have a thinning cost share program available for some counties. Contact Mr. Butch Bailey at 601-794-0671 to see if your timber will qualify.

Amy Myers: Give me a summary of what we've talked about today.

John Kushla: There are five beetle species that attack Southern pines. The southern pine beetle is the most damaging. Thinning pine stands can prevent bark beetle attack, but once established, southern pine beetle spots must be actively controlled. The attacking beetle should be identified.

Amy Myers: Today we've been speaking with John Kushla, Forestry Specialist. I'm Amy Taylor, and this has been Farm and Family. Have a great day.

Announcer: Farm and Family is a production of the Mississippi State University Extension Service.

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