What attacks fruit and blossom trees: diseases the sources name
A register of the bacterial, fungal and rust diseases that North Carolina State, the Morton Arboretum and Forest Research tie to apple, pear, plum and cherry trees: which trees each page names, where each is recorded, the season each source mentions, and where the full profile is.
Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.
This page reports what the named sources say. It is not a diagnosis of any tree and does not say what should be done with one. Each row names its source, all read on October 9, 2026. Where this site has a full profile, the row links it, and the regulated status tables are on the linked pages and are not repeated here. Two fruit-tree species have their own records, wild cherry and wild service tree, from the British and European forestry bodies, and black cherry from the US federal handbook.
The register
| Agent | What the sources record |
|---|---|
| Fire blight, Erwinia amylovora. Full profile | Kind: Bacterium Hosts: NC State Extension says it infects flowers, shoots of the year and rootstock of apple, and occurs on over 75 kinds of tree and shrub, among them pear, quince, cotoneaster, hawthorn, serviceberry and crabapple. Where and status: NC State says it has been reported in all major apple-growing regions of the United States. No regulated status is given. Season: NC State says wilting on infected blossoms may show one to two weeks after petal fall, rootstock blight is usually seen in late summer or early fall, and the bacterium overwinters in cankers left by infection in an earlier season. |
| Black knot, Apiosporina morbosa. Full profile | Kind: Fungus Hosts: The Morton Arboretum says plum and cherry are most susceptible, peach, nectarine and apricot less often infected, and that wild black cherry is commonly affected while sweet and sour cherries are less severely damaged. Where and status: The Morton Arboretum calls it a serious disease of plum and cherry throughout the United States. No regulated status is given. Season: Spores are released from early spring to early summer. The hard black knots do not appear until the second year of infection and the disease gets progressively worse each year unless managed. |
| Cedar-apple rust and related rusts, Gymnosporangium species. Full profile | Kind: Rust fungi that need two hosts Hosts: The Morton Arboretum says the fungus lives one full year on eastern red cedar and other junipers and the rest of its cycle on apple, hawthorn and other rose family plants, and that cedar-apple rust attacks susceptible cultivars of apple and crabapple. Where and status: The page names Illinois for the three most common rusts, cedar-apple, cedar-hawthorn and cedar-quince. No regulated status is given. Season: Spore horns swell on the juniper galls in the second spring, around crabapple bloom. Yellow-orange spots show on apple leaves in late spring, and spores are released from the leaves in late summer. |
| Bacterial canker, Pseudomonas syringae pv. morsprunorum, and silverleaf, Chondrostereum purpureum | Kind: Bacterium and fungus Hosts: Forest Research names them for wild cherry. It calls bacterial canker common and widespread, and says pruning wounds can also allow infection by the silverleaf fungus. Where and status: The species entry gives no place for them and no regulated status. Season: No season given on the page read. |
How the sources describe the effects
NC State calls fire blight devastating: shoot tips bend into a shepherd's crook, leaf mid-veins and the whole shoot blacken, and a canker at the rootstock can girdle and kill a tree. The Morton Arboretum says black knot may over time stunt or kill the tree because the knots cut off water and nutrients to the branches, and that infected trees may produce few flowers or fruit. For cedar-apple rust it says repeated infections can be unsightly and seriously weaken susceptible plants, and that infected leaves of apple and crabapple may drop, more severely in dry summers. Forest Research says the bacterial canker of wild cherry can be very disfiguring and sometimes fatal, and silverleaf can be a progressive and often fatal disease.
Profiles on this site
The full profiles linked in the table are fire blight, black knot and cedar-apple rust. Bacterial canker and silverleaf have only the row above, because the page read gives too few separate facts for a page each.
Who the sources say to report to
The Forest Research wild cherry entry carries a link to report a suspected case through TreeAlert and names no notifiable agent. The NC State and Morton Arboretum pages name no report line. The reporting offices for each country are on the report a pest in the United Kingdom and report a pest in the United States pages.