3 Truths About the Oak Gall Wasp You Never Knew

Gouty and horned oak galls are lumpy, tree growths found on tree twigs, leaves, and branches. Interestingly, trees produce woody deformities when prompted by chemical stimuli that interfere with normal plant cell growth. The culprits behind the chemical interference are the gouty and horned oak gall wasps. Read on to learn three truths about these insects you never knew.

1. Oak Gall Wasps Don't Harm Humans

Unlike their larger stinging cousins, these wasps are not harmful to humans. In fact, their stinger only pierces woody surfaces in order to lay their eggs. However, the larvae that emerge later from eggs produce the chemicals that prompt the formation of galls.

Galls are made of woody tree tissue and don't cause harm to the tree. Large numbers of galls may detract from a tree's appearance, but a widespread and heavy infestation may weaken a tree and cause early death.

2. Oak Gall Wasps Love Many Oak Species

Oak gall wasps are partial to several species of oak trees. They favor pin, scrub, scarlet, black, and red oaks as the ideal location for their eggs. After larvae emerge from their eggs, they thrive on the tissue of the gall the tree formed during their incubation. Eventually, the larvae abandon the gall which remains on the tree and hardens.

3. Oak Gall Wasp Control Can Be Tricky

Because oak galls do not usually kill a tree, few people worry about attempts to control the oak gall wasp. Remember, only very large numbers of galls are sufficient enough to completely halt water and nutrient movement inside twigs.

Wasp control is possible with the use of pesticides. However, control is tricky because pesticide application must be timed with the presence of adults or larvae. Additionally, very large oak trees are difficult to spray due to their height as well as the sheer number and size of their branches.

One way to eliminate and help lessen insect populations is to collect and destroy galls from infested trees when they fall to the ground. These galls can still host the wasp. Pests that overwinter in small, developing galls can be removed and destroyed. Even leaves that fall to the ground from an infested tree are capable of harboring pests and should be destroyed.

Finally, help a tree remain strong enough to withstand normal infestations of oak galls and wasps. Make sure the tree receives water during dry spells. Regular fertilization helps the tree maintain health as well.