Why are these trees sick?
April 13, 2009 6:54 PM   Subscribe

A lot of the Black Walnut trees in the area are dying. I can't quite figure out why. Common trait, most lost a lot of bark just before they died or just after. Some locals blamed a wet spring last year but I'm looking for something more specific. At least 10 trees last year, most over 10 years old, many older, have died within our little village of less than a city block. Central Pennsylvania. Any ideas?
posted by Toekneesan to Home & Garden (5 answers total)
This article talks about a number of pests and rots that can affect black walnuts. Someone at the Penn State Extension Service Outreach might have more information about what is going on and how to combat it.
posted by Sidhedevil at 7:01 PM on April 13, 2009

Look anything like this? [pdf]
posted by zennie at 7:07 PM on April 13, 2009

I found this...
Oct. 5, 2007 - Insect-disease complex killing black walnut trees in Boulder
Paul Bousquet, Parks and Recreation, (3030 413-7239
Jodie Carroll, Media Relations, (303) 441-3155

City of Boulder Parks and Recreation forestry staff have identified 250 dead or dying black walnut trees on public and private property in Boulder. The trees are suspected of succumbing to the "Walnut Twig Beetle/Canker Complex," a rapidly spreading disease currently impacting Front Range walnut trees. These 250 trees must be removed within the next four months to prevent further spread of the complex and additional tree losses.

The affected trees are scattered throughout the city with the most significant concentrations in the Whittier and Goss Grove neighborhoods. All affected trees on city property will be removed this month. Due to the large number of affected trees on private property (and the life cycle of the beetle), the city is allowing property owners until Feb. 1, 2008 to remove and properly dispose of dead or dying walnut trees on their property (B.R.C. 6-6-2, "Protection of Trees and Plants"). Property owners with diseased trees will be notified by Monday, Oct. 15, that they must remove these trees.

The recently-identified Walnut Twig Beetle/Canker Complex is thought to be the result of a combination of factors including impacts from the 2002 drought, infestation by the black walnut twig beetle (Pityophthorus juglandis) and the Fusarium fungus.

The tiny walnut twig beetle is relatively new to Colorado, is very aggressive and will attack both healthy and stressed trees. It is also likely the walnut twig beetle plays a role in transmitting the Fusarium fungus to other walnut trees, similar to how Dutch elm disease is spread by the elm bark beetle.
posted by JayRwv at 7:11 PM on April 13, 2009

Response by poster: Not seeing any cankers or beetle tunnels. Bark comes off in patches, like sunburned skin. The breaks are usually vertical—up the tree—and then falls off in patches.
posted by Toekneesan at 7:14 PM on April 13, 2009

Response by poster: Yeah, Fusarium. I've been considering that too. At least a partial factor. As it is in most insect infestations.
posted by Toekneesan at 7:16 PM on April 13, 2009

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