Balls from Insect Galls

Posted By Wolf Ridge Naturalist
September 26, 2016


Goldenrod insect gall, photo by Rod Keuhn

This past week during a phenology hike, we came across a strange growth on an unknown plant which led us into some further research, discovering that it is something referred to as a gall. Some galls can be a result of infections by bacteria, fungi, or nematodes, but they can also be the result of a female insect laying her eggs on a specific plant, choice dependent on her species, where saliva or other fluids influence the plant tissue and result in excessive growth in that area. This becomes the shelter and food source for the offspring until they are grown enough to make their way out, while at little to no cost to the plant. How the gall is formed is still a mystery in part, however, it is suggested that it caused by insect fluids having an impact on the hormones of the plant and therefore its gene expression.


These galls can be found on a variety of plant species, usually on the stem, leaves, or buds and can be formed by insects such as wasps, flies, caterpillars, beetles, etc. Based on the plant species chosen, location on the plant, and appearance of the gall, one can determine the insect species responsible for these excessive growths.


By Erika LeMay, Brooke Piepenburg, & Jarrod Klopp