City Planners Unwittingly Create a Haven for Gall Damage

Apr 27, 2018

Credit SC Public Radio

Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow.   History is filled with examples of municipalities choosing a favorite species for their main street trees to devastating results.  Central Park In the early 1980’s was  losing more than 100 elms every year.   In Denver, 1.45 million ash trees will die from the Emerald Ash Borer unless they are treated every two years with a systemic insecticide.

Horned oak galls are only occasionally so numerous as to damage trees. But in several boroughs of New York , over use of pin oaks  has created a perfect storm for over infestation. The tiny wasps that cause the galls are poor fliers and usually are geographically limited in movement. But with tens of thousands of pin oaks planted side by side, they move just a few yards to find another host. City arborists are making systemic insecticide injections to save some surviving individuals.