Leaf drop, slime flux, webworms take toll on drought-stressed trees

With the lack of rainfall over the past month, our plants and trees are beginning to show the stress from lack of water.

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One of the problems that I have been seeing is premature leaf drop.

I have a sweetgum tree in my yard that has dropped about half of its leaves. When trees drop their leaves early, they should have enough energy stored to come out and do fine in the spring. Sometimes, if they drop their leaves early enough, they will put on new leaves before fall.

Another tree problem that I have received calls on this past week is slime flux, or wetwood.

Slime flux is caused by bacteria. The bacteria can enter the tree through wounds or cracks in the bark. These wounds can be above or below ground. It can take years for the bacteria numbers to build up to levels where damage can occur in the tree.

Once the bacteria builds up large numbers, they will start a fermentation process in the tree. This process will produce pressure in the tree and cause a liquid to ooze from the tree. Since this is a fermentation process, the liquid contains a type of alcohol. Alcohol flux is nearly colorless and acidic and gives off a pleasant fermentative odor.

The wetwood or slime flux will have slimy appearance and texture. It has a foul, sour odor and will discolor the wood and bark of the trunk. This liquid will be under pressure when it comes out of the cracks in the bark. I have seen the pressure associated with slime flux so great that you could hear a hissing sound as the gas and liquid escaped.

Slime flux can infect numerous species of hardwood trees in our area. I have seen oaks, elms and yellow poplar infected with slime flux. The tree that I have seen the most with slime flux is the oak tree. It can infect trees at different ages, but older larger trees are infected most often. I have seen young trees under stress have slime flux as well. I have seen some young trees that were transplanted within the past year have numerous slime flux sites on their trunks. Young trees infected with slime flux have a greater chance of dying from the disease.

Trees that have been infected with slime flux in severe cases can show some wilt in the top of the tree, and some branches might die. However, the most common problem is some disfiguring appearance on the trunk.

The wood in the area where the liquid seeps out will die. The tree will seal this area off and the tree will survive. Over time, a hollow area will appear at the site.

To protect a tree from slime flux, keep it as healthy as possible by mulching around it, fertilizing and watering it. There are no pesticides or chemicals that can be used to control the infection.

The next problem that I have seen is the fall webworm.

Fall webworm has one of the widest host ranges of any caterpillar. In our area, you will find them on walnut, elm and a host of other trees, but pecan is the one that is infested most. Fall webworms usually will eat some of the leaves off the limbs in the area of the web, but they don't defoliate the tree.

The adult moths will emerge in June to July and begin laying egg masses on the underside of leaves. When the eggs hatch, the young larvae feed together. They will skeletonize the leaf and then start to form their web of silk, incorporating leaves and branches into the web. The young larvae do all of their feeding in the tent.

When they run out of food, they make the tent larger. If you look into the tent, you will find leaf fragments, droppings and cast skins. When full grown, the caterpillars leave the tent to find a protected area to spend the winter.

How do we go about controlling fall webworms? The best way to control them is to remove the web from the tree as soon as you see the webs forming. You can use a pole pruner to reach them and remove the portion of the limb that has the web on it. Since fall webworms don't feed outside of the web, this will remove all of the caterpillars. There are insecticides available, but they can be hard to apply since most of the webs are high in trees. As for burning the webs out, this will cause more damage to the tree than the caterpillars, and it is a fire hazard.

Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.