Green Horizons

‘Old’ Threat: EAB It does not appear the emerald ash borer (EAB) has spread beyond Wayne County, where it was spotted last year, to other parts of Missouri. This spring, traps were placed around the U.S. Army Corps of Engineers’ Greenville Recreation Area at Lake Wappapello, where the first infestation was discovered. Scientists thought the beetle would travel on firewood, so crews also set out traps at campgrounds and parks as far north as Maryville and as far south as Table Rock Lake.

Over the last few weeks, Federal and state agriculture officials have been picking through more than 1,000 sticky traps looking for “the green menace.” To date, more than half of the traps have been searched with no sign of the emerald ash borer.

‘New’ Threat: Walnut Twig Beetle and Thousand Cankers Disease of Black Walnut Within the past decade an unusual decline of black walnut (Juglans nigra) has been observed in several western states. Now the threat is trying to move east.

Initial symptoms involve a yellowing and thinning of the upper crown, which progresses to include death of progressively larger branches. During the final stages, large areas of foliage may rapidly wilt. Trees often are killed within three years after initial symptoms are noted. Tree mortality is the result of attack by the walnut twig beetle (Pityophthorus juglandis) and subsequent canker development around beetle galleries caused by a fungal associate (Geosmithia sp.) of the beetle. A second fungus (Fusarium solani) is also associated with canker formation on the trunk and scaffold branches. The proposed name for this insect-disease complex is thousand cankers.

So little is known about this disease complex that the Missouri Department of Agriculture and the Missouri Department of Conservation are co-sponsoring a national conference Nov. 3-4 in St. Louis. For more information about the conference or to register, contact Bonnie Russell at 573-522-1109.