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Helping farmers find, destroy, and manage EFB

Expansion of Cankers

John Pinkerton, Jay W. Pscheidt

Cankers of eastern filbert blight continue to expand each year. Cankers elongate from a few inches on small branches to over 3 feet on large diameter branches of susceptible cultivars. Cankers also expand around the branch. New rows of stromata are formed along the margin of the canker each year.

Dieback of branches occurs when expanding cankers girdle the limb. Leaves on these branches may remain attached for some period after death.

The main growth of the fungus occurs in the primary phloem tissues before the vascular cambium resumes activity in the spring. Fungal growth in the phloem stops when the cambium resumes activity and forms a callus layer to wall off further canker expansion. The fungus, however, invades the new xylem for a short distance. This allows the fungus to expand into the new phloem the following year.

When the branch dies, the fungus dies also. The fungus must have live tissue to grow and reproduce. Unlike many other canker fungi, EFB does not survive in dead, dry tissue. Cankers, however, can continue to produce spores after a branch has been removed from a tree and remains moist through spring.

Cankers continue to grow and, along with many new infections, kill the tree after 3 to 7 years.
Cankers continue to grow and kill the tree after 3 to 7 years
Photo by Jay Pscheidt, 1988.

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Cankers continue to grow year after year. Original infection is near the center of this oval canker.
Cankers expand
Photo by Ron Cameron, 1976.

When the canker finally girdles a branch the leaves rapidly wilt and die due to lack of water. The brown leaves may remain attached to the branch for some time.
Brown leaves may remain attached to the branch for some time.
Photo by Jay Pscheidt, 1992.

Dead leaves may remain attached to a branch. Use this symptom to scout for cankers in tall trees.
Dead leaves may remain attached to a branch
Photo by Jay Pscheidt, 1990.

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