Disholcaspis quercusmamma

Oak Rough Bulletgalls are at the hub of a buzz about wasps and flies swarming oaks belonging to the white oak group. The sturdy galls are produced under the direction of the tiny gall-wasp. The gall structure includes extrafloral nectaries that exude nectar to entice stinging and biting insects that provide protection.

I received several complaints this past week from homeowners and professionals about large numbers of stinging insects buzzing oaks in Ohio landscapes. The most recent involved an oak next to a Columbus playground.

Rough Oak Bulletgalls induced by the gall-wasp, Disholcaspis quercusmamma (family Cynipidae) are splitting through the bark and rising on the stems of oaks in the white oak group in southwest Ohio. The galls are most commonly found on bur (Quercus macrocarpa), white oak (Q. alba), and swamp white oak (Q. bicolor).

Several stem galls on oaks (Quercus spp.) that are produced under the direction of gall wasps (family Cynipidae) are called “bulletgalls” owing to their bullet-like shapes. Two of the most common found in Ohio are Rough Oak Bulletgalls induced by the cynipid wasp, Disholcaspis quercusmamma, and Round Oak Bulletgalls induced by D. quercusglobulus.

Dave Shetlar (Professor Emeritus, OSU Entomology) and I have recently observed newly developing oak rough bulletgalls in central and southwest Ohio, respectively. The galls are produced under the direction of the gall wasp Disholcaspis quercusmamma (family Cynipidae). We're also starting to see the gall's security detail, but more about that later.

Participants at last week's Ohio Plant Diagnostic Workshop in Secrest Arboretum (OSU OARDC) viewed the round, pointed galls produced by the Oak Rough Bulletgall Wasp on its namesake host. They also observed – at a distance – the buzzing security detail protecting the immature gall wasps developing within the galls.