Strange and Unusual Bug Symptoms-
Galls, Twig Girdler, Spittlebug and Slime Mold

One of the most fascinating, and sometimes disturbing, phenomena in the world of plant problems is the gall. Gall formations have been observed in this area on red oak (cottony gall and apple gall), live oak (gouty oak gall), hackberry (nipple gall), pecan (phylloxera) and live oak (red "berry galls" on the bottom side of leaves). We might as well "enjoy" them. Spraying after you see galls won't make them disappear. They're part of the leaf, not the insect that causes them. Preventive spraying, repeated several times earlier in the year, possibly could have reduced the population of these tiny, wasp?like insects that cause this growth. Despite their undesirable appearance, they don't kill or even maim trees.

Galls are caused by many species of mites and insects that feed and grow completely protected inside the gall structure. The most prominent family of insects causing galls is the Cynipidae, or the Gall?fly family. Galls made by mites and aphids have openings from which the young can escape. But with gall?fly, the gall is completely enclosed, and a hole must be made by the insect in order to emerge.

Each species of gall insect infests a special part of one or more particular species of plant, and the gall produced by each species of insect is of a definite form. They develop under some stimulus from the insects that lay their eggs in the plant tissue. The nature of the stimulus is not yet understood, but is dependent on the insect's acute chemical sense that enables it to recognize by smell and taste many essential oils and other substances in particular plants. One can speculate that the insect secretes some growth regulator that causes the nucleic acids in the plant tissue to program the abnormal development. In the case of the gall?fly, the gall forms after the larvae develop from eggs.

Actually, most gall formations are not injurious to the plant. This is fortunate because control is practically impossible when the insect is protected inside the plant tissue. Effective control-spraying could be made at or before egg laying time. This would be a preventive spray with an insecticide. The most logical time would be when the new leaves first emerge from the bud in the spring. However, it is difficult to decide whether or not the expense of spraying is warranted. This remains an individual decision.

As with many other plant problems, it is again important to recognize the malady, understand the probable extent of its damage, and realize that once the gall appears, it is too late to spray.

Relevant to our live oak galls and live oak twig blight, a preventive spray at bud break in the spring with a fungicide (Kocide) and insecticide?miticide (Orthenex or Diazinon) should prove to be a rewarding practice-at least from an aesthetic point of view. With this in mind, the gardening calendar should be marked now for a preventive spray at bud break time next spring if you have had reoccurring instances with these problems.

The twig girdler is also a concern to some folks. Fallen branches, usually not over ½- inch in diameter, are found neatly girdled as if by a whittling knife. But it's no man or boy sitting up in that pecan, elm, ash, mimosa, poplar, or several other varieties of trees. It is a beetle about 1-inch long. Their antennae are as long as their body. They have very strong mandibles that they use to cut through twigs and branches. The females do this pruning, sometimes spending 2 days to girdle the stem as they lay their eggs inside the portion of the severed limb. Twigs begin to fall to the ground usually in late summer. This grayish, ugly insect causes little damage generally, but when females are numerous, excessive girdling may occur.

Chemical controls are effective when timed properly. Sprays containing malathion, sevin or other general purpose sprays that are currently available, should be applied to trees when the first damage is detected. Three applications of spray at 2?week intervals are usually necessary to prevent damage. Infestations can also be reduced by gathering and burning all of the fallen twigs so that the eggs and larvae of "Girdling Gertie" are destroyed.

The spittlebug found on the twigs and branches of pecan trees or grape vines also causes a great deal of concern. The spittlebug appears around the buds and tender shoots as masses of frothy, white foam that looks like a mass of human spit. Often this is mistaken for a fungus or disease. Actually, inside this mass of white foam is a tiny light green insect known as the spittlebug. The frothy mass produced by the spittlebug presumably protects the young insect from other parasitic-type insects, and maintains an artificial high humidity required for the insect's development.

The adult resembles a leafhopper and flies actively during the summer. The spittlebug has not been known to cause any significant injury on pecans or grapes in Texas, and control measures are not generally recommended from the economic standpoint.

Finally, the last but certainly not the least, abnormality of concern is a group of fungi known as slime molds which often covers grass with a dusty bluish?gray, black or yellow mass. Slime molds are not parasitic on grass, but they are unsightly. They feed on dead organic matter. The most damage they do to grass plants is to shade and discolor the blades.

Slime molds occur usually after heavy rains or watering, but will disappear as soon as the turf grass dries out. The large masses of spores may be a nuisance because of the abundance of dark spores that rub off on shoes and clothing. They can be broken up readily by sweeping the lawn with a broom, or spraying with a strong stream of water.

So, if you see some of these "strange" plant symptoms in your landscape, fear not. What you see has happened before and will, in all probability, happen again. It just so happens that this time, it is happening to you!