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By Trey DeLoach and Don Bales

The Southern Pine Beetle (Dendroctonus frontalis Zimm., SPB) is the most destructive forest pest in Mississippi. The SPB has been killing pine trees in Mississippi for over 200 years. When conditions are favorable, these beetles can easily kill trees over several acres and some spots may grow to hundreds of acres in one location. In this article we will discuss how to recognize a SPB attack, how they spread, ways to control them, and ways to prevent attacks.

How to recognize a SPB attack?

The most noticeable indication that something is wrong with your pine trees is discolored foliage. The needles will first fade to a yellowish color, then red, and finally brown with in 1 to 4 months of the initial attack. The fading color from your foliage is not a sure sign that your pine trees are being attacked by SPB. There are other environmental factors that may kill your pine trees, but when you notice your pine trees dying you should inspect them to determine the cause.

The next thing you might notice are pitch tubes. Pitch tubes form at the place the beetles enter the tree. SPB pitch tubes are normally white and about the size of a dime. They are usually found in the crevices of the bark on the trunk of the tree.

After seeing both of these symptoms, how do you know if the dead or dying pine trees are infested with Southern Pine Beetle (SPB)? Remember there are other factors that can cause your crown foliage to fade and there are other bark beetles that will bore into and kill your pine trees. However the SPB is the only one that will spread and kill large numbers of your trees.

The only positive way to identify a SPB is to peel off a section of bark from the dead or dying trees. Those that are just beginning to turn yellow may be the best ones to inspect. The pattern of the galleries in the inner bark along with other indicators will reveal which beetles are present. It is not uncommon for trees to have more than one kind of bark beetle at one time.

The galleries of the SPB will be winding, frequently overlapping, S-shaped, and packed with frass except where the male and female are working. Frass is the sawdust-like material left behind by feeding adult beetles. If you see galleries that are "Y" or "H" shaped and not packed with frass, then the Ips beetle has created these galleries.

How do they attack and spread?

The female beetle is the first to attack a susceptible pine. They produce a chemical attractant that attracts other beetles to the same tree. The attacks first occur on midstem, then move above and below. When the tree is fully occupied the male beetles produce a chemical scent that lets other beetles know that the tree is occupied. When this occurs the beetles switch their attack to surrounding trees.

Once inside a host tree the beetles mate, and construct the winding galleries in which the eggs are laid. During this time the beetles are introducing the blue-stain fungus, which penetrates the wood, and plugs up the water conducting system of the tree. When all the eggs are laid the adult beetles emerge and attack other trees.

The young pupate and feed on the inner bark as they develop. Under ideal conditions adult beetles can develop in as little as 30 to 40 days. So in our part of the country we may have up to seven generations of beetles in a single year. The amazing fact is that the number of these beetles may increase by 10 times in a single generation.

So how do we control them?

We have talked about how to recognize a SPB attack and about how rapidly the population can grow. So, now how do we control them? The SPB will often require control. When SPB is detected, control depends on the stage of attack, season of the year, and other factors.

As a general rule, SPB spots will show a trend to spread in one direction. When that direction or "Head" is determined, it is advisable to mark for harvest all dead and dying trees in the spot and to mark for harvest a buffer of uninfested trees 40 - 80 feet wide. The width of buffer should be widest in the direction of spread. The width of the buffer strip also depends upon the severity and stage of infestation. Harvest and removal is recommended. For small spots where salvage harvest is not feasible, it is often advisable to cut and leave. Research has shown that felling the infested trees will disorient the SPB and interrupt their life cycle.

SPB control is not always necessary. In some cases, the spot will have run its course before it is discovered and will no longer be "active". An active spot is one in which there are trees on which the foliage is beginning to fade, and there are fresh attacked trees. A thorough understanding of the life cycle of the SPB is necessary to determine control options and priorities.

How about protecting my pine stand?

Simply put, pine stands are more likely to be attacked when under stress from overcrowding. Pine stands should be thinned throughout the life of the stand to keep them healthy and actively growing. "Stagnated" timber stands that are not actively growing are more susceptible to attack by SPB. Even a well-managed stand could be attacked in high outbreak year.

This would be an excellent year to make a habit of inspecting your pine stands once a month or so for the presence of SPB. There are SPB outbreaks occurring across Mississippi this summer so this would be a good time to begin inspecting your property. However, don't overreact if you find what appears to be a SPB attacked pine tree. You may wish to consult with your favorite professional forester for advice if you encounter pine beetles on your property.

See USDA Agriculture Handbook Number 558, "A Field Guide for Ground Checking Southern Pine Beetle Spots", by Ronald F. Billings and Herbert A. Pase III. And USDA Agriculture Handbook Number 634 "Identification and Biology of Southern Pine Bark Beetles", by R. C. Thatcher and M. D. Connor. This material is the best I have seen. It contains the procedure used by the U.S. Forest Service to determine the type and timing of SPB control. Check with us for a copy of this material. If you have internet access, there is an excellent site where you can view the handbook by the USDA Forest Service. The address is http://everest.ento.vt.edu/~salom/Hndbk558/558.html. Much of the material for this article was derived from the site. This handbook shows how to recognize various stages of SPB attack, how to decide if control is needed, and how to mark buffer strips for control crews.