Contents: By Damage and Image
Cynipid gall wasps on oak- Bassettia ligni, Andricus californicus, Besbicus mirabilis, and Neuroterus saltatorius
There are several cynipid gall wasps that make galls on oaks in the PNW. One potentially damaging cynipid gall wasp in nursery production is Bassettia ligni, a native insect that causes twig galls on Oregon white oaks.
In nurseries, the damage is more impactful. Twig galls caused by the B. ligni, cause the affected terminal to die, stimulating lateral branches to grow. While in some cases, this might provide a preferred bushier tree, sometimes this damage is a less appealing witches broom or other distortions, requiring retraining of another terminal.
Abraham, Melika, G. 2007. Review of the Nearctic gallwasp Species of the Genus Bassettia Ashmead, 1887, with Description of New Species (Hymentoptera: Cynipidae: Cynipini). Acta zool. hung. 53, 2007
Larew, H. and J. Capizzi. 1983. Common Insect and Mite Galls of the Pacific Northwest. Oregon State University Press.
Shaw, Dave. 2015. Summer 2015 DROUGHT! And heat. A Forest Health Report. Tree Topics. Oregon State University Extension. Posted September 2 2015. <18 July 2016>
Shaw, Dave. 2013. Oregon white oak in the Willamette Valley, 2013 . . . Some in your face issues. Tree Topics. Oregon State University Extension. Posted 2013. <18 July 2016>
Garry oak leaf and twig gall. PNW Insect Management Handbook.
Original version: <18 July 2016)
Last revision <19 July 2016>
Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University/NWREC.
Close up of a cynipid wasp inserting egg (ovipositing) on bur oak