Contact: Joe Pase, (409) 639-8170
LUFKIN - As if wildfires weren't enough, the prolonged drought is fueling another pestilence that is killing pine trees in East Texas, says an official with the Texas Forest Service.
The engraver beetle, which usually breeds harmlessly in fresh logging debris and weakened trees and doesn't kill enough pine trees to be considered a major pest, is thriving in this hot, dry weather. This small insect, also called IPS beetle, appears to be attacking and killing trees weakened or stressed by the drought, says Joe Pase, an entomologist with the Texas Forest Service Pest Control Section here.
So far this summer, there have been several instances where the beetles have killed 20 to 30 trees in a single infestation, Pase says.
There are several species of bark beetles that attack and kill southern pines.
The southern pine beetle is the most serious insect pest in the southern forests of the United States. It is capable of killing large numbers of trees and a single infestation may encompass hundreds of acres. Populations of southern pine beetles fluctuate from year to year in east Texas, and all indications are that 1996 will be a low year for this insect. During 1985, the worst year on record, more than 15,000 infestations caused by southern pine beetles were reported in east Texas.
It is important to determine which of the bark beetles has attacked a tree. All of the beetles chew holes through the bark and feed and lay eggs in the inner bark (the area between the bark and the wood). The three species of engraver beetles construct distinct "Y-," "H-," or "I-" shaped galleries as they lay their eggs in the inner bark. The small southern pine engraver usually constructs the "I-" shaped gallery.
As the beetles construct these egg galleries, the pattern is etched on the inside of the bark as well as the outer sapwood of the tree. The presence of the "Y-," "H-," or "I-" shaped gallery pattern that tends to be oriented vertically up and down the tree is the easiest way to identify engraver beetle attacks.
The southern pine beetle constructs a winding, "S-" shaped gallery. The gallery of the black turpentine beetle has no particular shape, but the attacks of this beetle are usually limited to the bottom 6 to 8 feet of the trunk of the pine tree. It is a good idea to remove some bark from a recently attacked tree to look for the distinct gallery pattern made by the adult bark beetle.
Although it is often overlooked, the first sign of attack by engraver beetles is the presence of reddish-brown boring dust in the crevices of the bark.
When a tree is healthy and has a good supply of moisture, sufficient pitch or resin will be produced such that globs of resin, called pitch tubes, will form where the beetles attack the tree. These pitch tubes often will have a reddish-brown appearance because of boring dust mixed with the resin.
During periods of drought, pitch tubes may not form on the bark of the trees and only the boring dust will be visible. Once the tree becomes colonized by engraver beetles, it will soon die.
The next visible characteristic of attack will be the foliage (needles) of the tree turning from green to yellow to red.
During the summer months, the tree's foliage will turn from green to yellow in about three weeks. Pine trees seldom survive when they have been attacked by engraver beetles. It is important to keep in mind that engraver beetles may have attacked the upper portion of the tree and killed the top but have yet to attack the lower portion of the bole where a person could reach while standing on the ground.
Maintaining a healthy stand of trees is a landowner's best policy for preventing engraver beetle attacks. Good forest management practices also are good beetle prevention practices. If direct control is needed for an infestation of engraver beetles, cutting and removing the infested trees is about the only feasible course of action to follow.
During this time of drought when pine trees are stressed, landowners are encouraged to keep a close watch of their pine stands. If engraver beetles attack, direct control may be warranted. For more information, contact the Texas Forest Service office nearest you or the Pest Control Section, (409) 639-8170.
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