Galls on Oak Trees

R. Keith Collins  |  4/23/2013 8:52:29 PM

Commonly, the Oak Apple Gall is caused by the Oak Gall Wasp.

Unsightly galls have been appearing on Oak trees recently as they break dormancy and leaves begin to grow.  These are commonly the Oak Apple Gall caused by the Oak Gall Wasp.  Most gall wasps develop in two or three years in woody galls on the twigs or foliage.  Adult wasps emerge from twig galls in the winter, lay eggs in buds, then die.  When eggs hatch and new growth resumes on the Oak tree, salivary secretions of the wasp act as powerful plant growth regulators and force the tree to form the gall that protects the developing wasp.  Rarely does this damage the tree but heavy infestations, especially on young trees, may cause injury or death.  The galls secrete nutrients from the tree which is a food source for the grubs.  Chemical control in the gall stage is not effective.  To properly time spray applications, collect some of the galls and store in plastic bags outside in the shade.  When the wasps emerge, it is time to spray.  Wasps that develop from galls on hardened twigs will not emerge until winter.  Many wasps from galls from leaves and succulent stems (new growth) emerge in late spring or early summer.  Galls may be physically removed from small trees and destroyed.

Richland Parish County Agent Keith Collins offers his assistance to local clientele and may be reached by telephone at 318-728-3216, Monday through Friday, from 8:00 a.m. to 4:30 p.m.
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