Thomas County has its share of pecan trees. The county actually has nearly 3,000 acres of pecan orchards in commercial production. This ranks third on our list of agricultural commodities in Thomas County. There are many insect and diseases pests that pose as a challenge to pecan producers. Not only pests, but growers deal with agronomic issues, such as irrigation, that we cannot control with our yard trees. However, there are a few issues in yard pecan trees we can mitigate.

One of these issues being reported now is spots on the leaves. These spots are raised from the leaf and look more like small warts or tumors. They appear yellowish-green, circular and look very unsightly. The warts appear on almost all of the leaves. Some trees may have more warts than other trees.

These are actually galls resulting from the feeding of an insect call phylloxera. Pecan leaf phylloxera, Phylloxera notabilis, is a tiny aphid-like insect that feeds on foliage of pecan trees. You can only see the insects under a microscope because they are so tiny.

Their feeding causes rapid and abnormal growth of the leaf tissues. The tissue grows rapidly and encloses the phylloxeran. The proper term for the wart is a “phylloxera gall.”

The stem mothers hatch from over-wintering eggs just after budbreak, usually in April, and crawl to the expanding leaves where they settle down to begin feeding. They begin laying eggs inside the protection of the galls in mid-April. As the eggs hatch and the resulting phylloxera begin to feed, the gall enlarges. Usually in mid-May, the now-matured phylloxera emerge from the gall. Some of these may crawl to another spot on a leaf and produces a second generation of galls.

The bad news is that once we see galls, it is too late to control this season’s infestation. Treatment must occur at or following budbreak. It is very difficult to time this spray, and only commercial orchards have this ability. This is not an option for homeowners.

However, one insecticide can be drenched at the base of the tree trunk prior to the onset of phylloxera for control. This is an option for homeowners. UGA Extension entomologist Dr. Will Hudson and I are conducting research on this insecticide treatment now.

The study is to determine the timing of an insecticide drench to control pecan leaf phylloxera. The insecticide is a common insecticide that is taken up by the roots of the tree. The insecticide must be present in the tree limbs during budbreak. If we can determine the proper timing of this application, we can give recommendations on controlling phylloxera.

Hudson has an orchard under research in Athens, and I have one under research in Thomas County. We treated for phylloxera at different times over the winter. The treatments are complete, and the trials are ready to undergo ratings to determine which treatment is most effective. This treatment is very simple and can be accomplished by a homeowner who has persistent issues with phylloxera.

The good news is that leaf phylloxera is usually minor economic importance. Infestations must be severe to affect pecan production. There is another type of phylloxera called pecan stem phylloxera which attacks foliage, shoots, and even pecan fruit. This is much more damaging; however, I have never seen this type of phylloxera. We primarily have leaf phylloxera.

For additional questions, contact the Thomas County Extension Office at 225-4130.