Dutch Elm Disease - Symptoms and elm bark beetles

Vascular Wilts

Dutch Elm Disease - Symptoms and elm bark beetles

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Leaf symptoms

discoloration in elm

Vascular discoloration in xylem after removing the bark. Helthy xylem would be white.

Tyloses

Elms respond to infection by producing vascular occlusions with hosr responce chemicals (phenolics) and also morphological barriers like tyloses. Tyloses are cells along the vessels that ballon out into the vessle lumen causing a blockage.

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Root graft between two elm trees.

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European elm bark beetles

Galleries elm bark beetle

Egg laying galleries of the European elm bark beetle are made along with the grain of the wood (up and down)

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Egg laying gallery of European elm bark beetle with larval galleries coming out from the sides of it.

exit holes in elm

Exit holes in the bark where mature elm bark beetles left the tree. Adult beeltes carry the fungus causing Dutch elm disease from the diseased wood to healthy trees when they do their maturation feeding.

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Feeding site at twig crotch caused by the European elm bark beetle. As the beetle feeds on the healthy tree, spores of the fungus enter the xylem of the elm.

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Native elm bark beetles

native elm bark beetle galleries

Egg laying galleries of native elm bark beetle. Direction of the main egg laying gallery is across the grain.

elm bark beetle galleries in small branch

A relatively small branch with many North American elm bark beetle galleries. Even small diameter stems can be used for egg laying and lots of new beetles can emerge.

Galleries of both elm bark beetles

An elm log with galleries of both the European and North American elm bark beetles.

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Elm bark

elm bark

Tree inspectors often need to know how to identify elm in wood piles since having elm wood can serve as a place for bark beetles to bred. The bark of elm has very characteristic layering that other hardwood trees do not have.