Dr. Carol Mapes, professor of biology at Kutztown University, came to the Lehigh Gap Nature Center on Feb. 26 to talk about her favorite subject, plant galls.

It was the second in a series of nature talks to be held.

A hand-out included the names of 97 galls, each of which may have several subdivisions, but many galls have never been named, said Mapes. The study of galls is termed cecidology

Some galls can be damaging to farm crops such as the cedar apple gall that looks like an orange flower. It can cause rust spots on fruit and consequently cedar and apple trees should never be planted in close proximity.

Fungal galls damage cherries, peaches and plums. Damage at the roots and stems flows to the leaves and even damages other galls.

Many galls are native and are plant specific. However, most do not damage plants. They are difficult to control.

A round ball that forms near the top of a goldenrod plant is the goldenrod ball gall which provides a source of food for developing larvae. Some people collect the larvae as bait for fishing.

A larva makes a tunnel out of the ball for the fly to use in spring because the fly does not have any chewing parts. Woodpeckers will eat the larva.

Mapes said goldenrod is an invasive plant in Hungary where there are no galls to help keep it under control.

The cynipid wasp galls grow mostly on oaks and there are those that are specific to different types of oaks. The wasps come out of the gall in the springtime and enter an acorn.

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Biology professor talks about plant galls at Nature Center