As leaves begin to fall from their trees during the autumn season, you may find it easier to notice some very strange oddities growing in the forest. All types of bumps and growths may catch your eye, but what causes these curiosities may surprise you! Many of the growths you see in the forest are called galls, which are abnormal plant tissue that can be caused by the feeding or egg laying activities of insects like wasps!
Gall wasps are members of the cynipoidea family. They are minute insects that resemble ants with wings. The female gall wasp, although petite in size, has an ingenious way of protecting her babies.
Gall wasps will deposit their eggs under the bark of trees, in the leaf, twig, stem, bud, root, or even near the tree’s fertilized flowers in the spring. In response to the strange chemicals left by the wasp, the tree or plant will then stimulate growth in that area. This is called a “physiologic sink,” meaning that the tree is funneling resources to the gall, in an effort to minimize the strange new substance. This helps the gall wasp larvae grow as the tree provides food and shelter. Each species of insect that makes galls stimulates their host tree to produce a unique type of gall to protect their growing young. Many gall wasps are named for their curious shaped galls. The yellow wig, red cone, urchin, crystalline, and disc gall wasps have galls that allude to their names.
Most gall makers will lay their eggs in the spring, when new leaves emerge. As a gall develops, the larvae can face predation from woodpeckers, mice, parasitic wasps, and other bird species. The gall itself often tastes bitter (like the bitter bile produced by gall bladders, hence the name), which helps protect the larvae from predators. Gall wasps have a parasitic symbiotic relationship with their botanical host but, in most cases, do not excessively harm their host tree. A single oak tree was once found to be a nursery for 70 different species of galls at the same time!’
On Long Island, galls can be found on most species of trees and plants. The gouty oak gall (smooth) and the horned oak gall (horn-like projections) are both solid woody galls that can grow up to 2 inches in diameter. The galls begin their first growth on the underside of large leaves and look like blisters. The second stage is a mid-summer knotty twig gall that can take up to 2 years to fully mature! Adults emerge in the spring, and have only a few weeks to enjoy life outside of their gall before laying their own eggs and dying. Gouty oak galls are found on scarlet, red, pin or black oak trees; while horned galls are found on pin, scrub, black, blackjack, and water oaks. Oak apple galls are impressively large spongy galls that house only one developing wasp. These circular galls will sometimes fall with oak leaves in autumn, overwinter in leaf litter, and emerge as adults in the spring. Try looking for the exit
hole if you can spot one in an oak tree near you!
Among the multitudes of galls that you can find in the forest are the black oak twig gall, wool sower gall of oak, black knot gall
of oak, cedar apple rust, and the goldenrod bunch gall. Gall wasps are not the only gall making creatures in the forest. Mites, parasitic plants like mistletoe, and certain bacteria and fungus can also stimulate gall growth in plants, trees, and mushrooms. Chances are that if you look close enough on your next visit to the Refuge, you will spot one of these amazing adaptations of gall wasps.
By Cara Fernandes