Walnut Twig Beetle

Image
black walnut tree

Walnut Twig Beetle

Scientific Name

Pityophthorus juglandis

Walnut Twig Beetle
Image
Hero Aponi

This tiny beetle and the fungus it carries can greatly affect black walnut trees, a valuable source of wood and delicious nuts! 

Aponi
Image
WTB pencil
Field Guide
Image
Walnut Twig Beetle
Walnut Twig Beetle
Host Trees

Black walnuts grow to be a medium to large tree up to 100 feet in height and usually have a straight trunk and narrow crown under competition in the forest.

Image
Image
Black walnut tree

Branch end of black walnut showing the alternate arrangement of its large compound leaves.

Image
Black walnut compound leaves
Image
Walnut Twig Beetle
Host Trees

Grove of young black walnut trees

Image
Image
grove of young black walnut trees

The bark of the black walnut (Juglans nigra) is usually light brown, ridged and furrowed with a rough diamond pattern. Walnut has large compound leaves (12-24 inches long) each of which has 10 to 24 leaflets.

Image
Black walnut bark
Image
Aponi looking back
Tree Identification

To identify the black walnut in winter, look for tan buds that are alternately arranged on the stem. Leaf scars are 3-lobed, resembling a “monkey face.”

Image
Walnut twig branch

Cross section of a black walnut twig showing the unique chambered sections inside the twig.

Image
chambered pith of black walnut

Close-up of flower spikes on a black walnut tree. These appear in late spring, usually near the end of twigs and are 2.5-5.5 inches long (6-14 centimeters) long.

Image
Black walnut flower spikes
Image
Walnut Twig Beetle
Image
Black Walnut fruit

The young fruit of the black walnut is light green, round, and 2- 2 1/2 inches (5-6 centimeters) across.

Image
Image
Black walnut fruit

The husk of the walnut fruit turns black as it ripens in late summer to fall. Inside the husk you can find an irregularly furrowed, hard nut that contains sweet, oily and edible meat.

Image
Black walnut husk
Image
Hero Aponi
Symptoms

Yellowing leaves at branch ends can be an early symptom of dieback from Thousand Cankers Disease.

Image
Image
yellowing leaves as a result of thousand cankers disease
Image
Crown thinning and dieback as a result of thousand cankers disease

Black walnut tree in decline from Thousand Cankers Disease and showing dieback in the upper canopy.

Image
dieback as a result of thousand cankers disease
Symptoms

Tiny exit holes created by adult Walnut Twig Beetles as they leave the tree.

Image
Image
Exit holes from the walnut twig beetle

Close-up of bark showing small piles of sawdust created by beetle tunneling.

Image
Sawdust piles created by tunneling walnut twig beetles
Image
Walnut Twig Beetle
Damage

Example of a large trunk canker caused by the fungus Fusarium solani that can also occur on trees in advanced stages of decline.

Image
Trunk canker

Close-up of galleries created by Walnut Twig Beetle tunneling under the bark.

Image
Walnut Twig Beetle galleries
Image
Walnut Twig Beetle
Image
Damage

Dark staining caused by Geosmithia cankers in black walnut. As these cankers grow together they stop the flow of water and nutrients in the branch and dieback occurs.

Image
Image
Wood staining as a result of thousand cankers disease

Close-up of walnut branch showing the early stages of canker development around beetle tunnels.

Image
Cankers developing near tunnels
Image
Walnut Twig Beetle

Are you still curious about
the walnut twig beetle?

Click the button below to find more information and connect with the experts.

Walnut twig galleries and cankers: Ned Tisserat, Colorado State University, Size comparison to penny: Eric R. Day, Virginia Polytechnic Institute and State University,Top view, side view: Steven Valley, Oregon Department of Agriculture, .; Adults on penny, vial: Whitney Cranshaw, Colorado State University, Larva, adult, beetle galleries: Whitney Cranshaw, Colorado State University, Thousand Cankers Disease spores: Alan Windham, University of Tennessee, Cultured colony of thousand cankers disease: Ned Tisserat, Colorado State University,Black walnut tree: Vern Wilkins, Indiana University, Black walnut leaves: Paul Wray, Iowa State University, Grove: Robert Vidéki, Doronicum Kft., Bark: Jason Sharman, Vitalitree, Twig lobes,black walnut fruit: Rob Routledge, Sault College, Chambered pith, flower spikes: Paul Wray, Iowa State University, Husk: Lyndon Photography, Dried Botanical ID, USDA APHIS PPQ, Yellowing leaves, canopy dieback: Whitney Cranshaw, Colorado State University, Crown thinning and dieback: Curtis Utley, CSUE, Exit holes: Karen Snover-Clift, Cornell University, Sawdust, trunk canker, galleries: Whitney Cranshaw, Colorado State University, Wood staining: Ned Tisserat, Colorado State University,

Sign up for
our newsletter

Sign me up!
The Plant Heroes Team will send you important and helpful newsletters to your email