“I’m on the point, do I have to pay to have it trimmed? Or is it a waste of money because it has to be dismantled? “
There are no proven treatments for horned oak bile, said Daniel Potter, an authority on the field. He was motivated to study horned oak bile at the University of Kentucky in the 1990s when entrances to ornate horse farms were hit.
“It’s a long story,” he said. “In short, we don’t know how to get rid of it.”
A tiny, non-stinging wasp causes a horned oak bile. The wasps lay eggs under the skin of oak trees. Over the course of up to three years, the unsightly galls grow larger and reach the size of golf balls. Galls remove water and nutrients from small branches. The spines, like an overripe potato, are exit tunnels for wasp babies.
Potter said it was “impossible” to spray large oak trees. Instead, he and other researchers injected them with insecticides in the 1990s.
“We thought we could break the cycle by doing it three years in a row,” he said. “We did it four years in a row. It still hasn’t broken the cycle. … I am not aware of anyone having solved the mystery of how to handle this. “
He suggested pruning small breakouts. Full infestation, like all of St. Louis, is much more difficult. While he has seen bile go away on its own, he has also seen other trees become overwhelmed and die.