Tuesday, May 11, 2010

Hackberry Gall

Ever notice these grayish-brown blobs on the hackberry trees? These structures are galls. A gall is an abnormal growth of plant tissue. It can be caused by fungi, bacteria, mites or insects. In this case, it is produced in the plant when an insect lays an egg in the plants tissue. The adult insect that deposits the egg may inject chemicals that change the plants growth. In some instances, the developing larva controls the plant with physical or chemical ways.


The gall protects the developing critter from the elements and from some predators. (Some predators, like woodpeckers, have learned to look for the galls and the tasty treat that lies inside.)

Hackberry petiole gall. Photo by John Howard.
Hackberry trees have many types of galls associated with them. This one is called a Hackberry Petiole Gall . It is caused by a plant louse called a Hackberry Petiole Gall Psyllid, Pachypsylla venusta. The adult stage looks similar to a small cicada.

Hackberry Petiole Gall Psyllid by John Howard

Below is a close-up of the little critter. You can see its tiny orange wing buds on the sides of its body. As many as 13 nymphs can live inside the gall separated by compartments of wax.

The hackberry galls are very thick and tough. The Hackberry Petiole Gall Psyllid has sclerotized teeth on its abdomen that it scrapes across the inside of the gall until it is cut open. They emerge in the spring and molt into adults when new leaves are forming on the trees.

Photo by Osten-Sacken, University of Florida


One can never know what you may find when you start to look. This little creature is just one of the many amazing things that are out there in nature.

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1 comment:

dAwN said...

Oh my..who would have know a critter was there..Well You of course..
very interesting..and as always a wonderful informative post!