Signs of a pecan phyllexera infestation

Published 4:41 pm Friday, March 31, 2017

By Ty Torrance

Pecan trees across the county are beginning to break bud and leaf out.  This time of year it is common to run across different pest in an orchard or yard tree. I wanted to talk about one interesting pest in particular, The Pecan Phylloxera.

The first sign of a pecan phylloxera infestation is wart like galls on the leaves.  This is the result of feeding by an aphid-like insect called phylloxera, which causes rapid and abnormal growth of young leaf tissue to surround and enclose the female (called a stem mother). Although the insects themselves are rarely seen, 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.

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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.  There appear to be 2 species of phylloxera that infect the leaves—one, called Pecan leaf phylloxera seems to prefer immature nursery and orchard trees. The other, called Southern pecan leaf phylloxera prefers mature trees. In any case, the resulting damage will be the same.

Various species of both pecan and hickory can be infested with this insect.  Damage is primarily aesthetic.  If the infestation is severe enough it can cause premature defoliation.  However, since these insects don’t seem to heavily infest trees on a yearly basis they do very little long term damage. 

So what can we do about the Phylloxera?  Nothing!  By the time the symptoms appear the damage is done.  Nothing that you can use will penetrate the gall and the damage that the insect causes is just aesthetic.  You would have to apply an approved insecticide at bud break and cover the entire tree.  This would be virtually impossible in the home orchard and in most years would be unwarranted. 

So now you know more than you ever wanted to about the pecan leaf Phylloxera.  If nothing else, hopefully, this will help you sleep a little easier knowing that these pests are not doing too much damage to your trees.  Please call the Extension office with any questions (229-248-3033).  Information shared by UGA Extension Specialist Lenny Wells.