Issue 18, October 16, 2009
Thousand Cankers Disease of Black Walnut
Thousand cankers disease of black walnut is a lethal insect-disease complex affecting various walnut species. It has not yet been found in Illinois. It is present in western U.S. states and as far east as Colorado. The disease can kill walnut trees in three years. Initially trees are attacked by the walnut twig beetle, Pityophthorus juglandis. Two fungal cankers then invade around beetle galleries. The fungi are Geosmithia sp. and possibly Fusarium solani. Many small cankers kill the wood and girdle branches. The dark cankers can be seen by peeling away bark on affected branches. Cankers are as much as 3 cm or larger and each canker has a shallow tunnel near the center of the dead area. The tunnel is made by the walnut twig beetle.
There is quite a bit of interest in preventing spread of this disease complex. November 3-4, 2009, there will be a national conference on thousand cankers of black walnut. For those interested, the conference is quite close. It will be hosted by the Missouri Department of Agriculture and the Missouri Department of Conservation in St. Louis, Missouri. The conference registration fee is only $75.00 if you register before October 23rd. For information on this conference, click here to visit their web site.
A very good source of information on diagnosing Thousand Cankers Disease can be found on this University of Colorado web site (Adobe PDF).--Nancy Pataky
Author:
Nancy Pataky