2020 Fire Blight on Ornamental Trees

2020 Fire Blight on Ornamental Trees

Landscape & Garden    Treasure Valley

Caused by bacterium Erwinia amylovora

Posted on: July 1, 2020 by Nic Usabel

Spring conditions have amplified the effects of fire blight bacterium in not only pear fruit and apple fruit, but ornamental plants in the Rose family. Plants which may show damage include crabapple, flowering pear, pyracantha, hawthorn, cotoneaster, mountain ash, and other related plants. Current observations note widespread affects in the ornamental apples and ornamental pears.

Damage is typically noticed when twigs wilt and die. The tip of the plant growth exhibits a shepherd’s crook. Symptoms seen later in the season include progressive wilting of the branch as the bacterial canker advances down the stem.

For cultural control immediately prune out and destroy infected tissues. Make pruning cuts at least 6-8 inches below the infected tissues. Sterilize pruning tool(s) between cuts using 70% alcohol or 10% bleach solution.

Other control methods to reduce inflammation of fire blight are to avoid over fertilizing with nitrogen, to not sprinkle irrigate susceptible plants, and inspect plants carefully for cankers or blighted twigs during dormancy.

The best management of fire blight is to select ornamental trees which are resistant to the bacterium. Reference the Pacific Northwest Handbook links below for additional information.

https://pnwhandbooks.org/plantdisease/cultivar-tables/crabapple-cultivar-susceptibility

» https://pnwhandbooks.org/plantdisease/host-disease/pyracantha-firethorn-fire-blight

» https://pnwhandbooks.org/plantdisease/host-disease/hawthorn-crataegus-spp-fire-blight

» https://pnwhandbooks.org/plantdisease/host-disease/mountain-ash-sorbus-spp-fire-blight

» https://pnwhandbooks.org/plantdisease/host-disease/crabapple-malus-spp-fire-blight