American Elm - Disease information and Management Recommendations. 
HOST PLANT DISEASE SYMPTOMS MANAGEMENT
Elm, American 
Ulmus americana		 Cankers, Botryodiplodia sp. and others Slightly sunken reddish brown to black cankers form on twigs and small branches. Leaves turn bright yellow and remain attached to the branches for several weeks. Provide good growing conditions. Avoid mechanical damage. Remove dead limbs.
CHEMICAL: None.
Dutch elm disease, Ophiostoma ulmi First noticed as wilting of branches in the crown. Leaves turn yellow or brown and tend to remain attached to the tree for an extended period. (Yellow leaves may drop prematurely.) Inner bark exhibits dark brown streaking. Lab testing needed to confirm infection.
REFERENCE: Dutch Elm Disease, PP-324 (ND)		 Remove diseased trees and debark wood stored as firewood. Do not prune between April 15 and September 1 in the southern half of Minnesota. Where applicable, use a vibratory plow to disrupt root grafts and prevent disease spread.
CHEMICAL: Root flare injection of Arbotect 20-S to prevent infection of specimen trees. Consult a professional arborist.
Elm black leaf spot, also called elm anthracnose, Stegophora ulmea Yellow spots form on the upper surface of leaves followed by slightly raised black fruiting bodies. Promote plant health. Remove infected leaves in the fall.
CHEMICAL: Not warranted in home landscapes.
NURSERY: Bordeaux or mancozeb.
Oyster canker, Pleurotus ostreatus White rot fungus which enters through wounds or dead branches causing wood to become brittle and crumbly. White shelf mushrooms are produced after extensive rot has occurred. Uncommon in urban elms. Avoid improper pruning or unnecessary wounding. Promote tree health.
CHEMICAL: None.
Wetwood or slime flux, Enterobacter cloacae and other bacteria Bacteria ooze from openings on trunks and large limbs in a light brown, slimy matrix known as slime flux. This toxic material is responsible for the long bleached or dark brown streaks on trunks. If severe, leaves may exhibit marginal scorch. Keep trees healthy.
CHEMICAL: None.
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