Fire blight makes a tree look like someone held a blowtorch to its branches. Infected shoots, leaves, and blossoms turn dark brown or black, wilt dramatically, and stay attached to the tree, giving whole sections a scorched appearance. It’s one of the most visually distinctive plant diseases, and once you know the signs, it’s hard to miss.
Fire blight is caused by a bacterium that attacks plants in the rose family. Apple, pear, crabapple, hawthorn, quince, mountain ash, cotoneaster, and ornamental pear trees are all susceptible. The disease moves through the tree in a predictable sequence starting in spring, and each stage has its own telltale look.
Blossoms and Flower Clusters
The earliest visible symptoms usually appear within one to two weeks after bloom, though cool temperatures can delay them up to a month. Flower clusters are often the first thing hit. Infected blossoms develop a water-soaked, translucent look before wilting, shriveling, and turning black. The sepals and entire flower cluster darken and droop. Small fruitlets nearby wither and turn black or brown. These dead, blackened flowers don’t fall off. They cling to the tree through the growing season, which is a useful clue: healthy flowers that simply didn’t get pollinated tend to drop.
The Shepherd’s Crook
The most recognizable sign of fire blight is what happens to new shoot tips. The current year’s growth wilts at the tip and bends back on itself roughly 180 degrees, forming a hook shape that looks like the curved end of a shepherd’s staff. This “shepherd’s crook” is nearly diagnostic on its own. The wilted tip darkens to brown or black while the bend gives the shoot a drooping, defeated posture that’s visible from a distance.
Before the full crook forms, infected shoots first look slightly wilted, with leaves turning gray-green. Then dark streaks appear along the leaf midveins as the bacteria travel through the vascular tissue. Within one to three weeks, leaves and stems blacken entirely. On apple trees, dead leaves turn a dark orange-brown. On pear trees, they go fully black. In both cases, the brown or blackened leaves hang downward and remain attached to the twig well into winter rather than dropping normally.
A tree with multiple infected shoots can look like it survived a brush fire, which is exactly how the disease got its name.
Bacterial Ooze
During warm, humid weather, infected tissue produces droplets of sticky bacterial ooze. This is one of fire blight’s most distinctive calling cards. On apple shoots, the ooze typically has a golden or amber color. On other hosts and in different conditions, it can appear whitish and mucoid. You might spot these droplets on infected shoots, leaf stems, cankered bark, blossoms, or fruit. The ooze is packed with bacteria and is a major way the disease spreads to new tissue, carried by rain splash, insects, and pruning tools.
If you see sticky droplets on darkened, wilted tissue, that’s a strong confirmation you’re dealing with fire blight rather than a lookalike problem.
Cankers on Branches and Trunk
As the bacteria move deeper into the tree, they create cankers: sunken, discolored patches on branches, limbs, and sometimes the trunk. Overwintering cankers appear as slightly to deeply depressed areas of bark that look different in color from the surrounding healthy wood. The edges are often clearly defined.
If you peel back the bark around a canker, the sapwood underneath is reddish brown rather than the healthy pale color you’d expect. Deeper in the cambium layer, you may find red-brown streaking. In spring, cankers can weep bacterial ooze along their surfaces or margins during wet weather. These overwintering cankers are the launchpad for new infections each year. Shoots growing near an active canker often develop a distinctive yellow-orange discoloration at the tip bud and stem, which looks different from the darker brown-black of shoots infected later in the season.
Rootstock Symptoms
On grafted trees (which includes most commercial apple and pear trees), fire blight can reach the rootstock with devastating results. Infected rootstock bark may show water-soaking, purplish to black discoloration, or cracking. Bacterial ooze sometimes appears at the graft union within two to four weeks after canopy symptoms develop. In severe cases, the entire tree can collapse and die rapidly between late June and late July. A subtler warning sign is premature red fall color appearing in the canopy in late August or early September, well before surrounding healthy trees change color.
How It Progresses Through the Season
Fire blight follows a roughly predictable timeline. In early spring, overwintering cankers become active and produce ooze that spreads bacteria to open blossoms. Blossom blight symptoms show up one to two weeks after bloom. As the season progresses into late spring and early summer, shoot blight develops on actively growing vegetative shoots, creating the characteristic shepherd’s crooks and blackened branches. The window between petal fall and when terminal buds set for the year is the most dangerous period: shoot infections during this time cause the greatest limb and tree losses.
Severe weather events like hail or strong winds can trigger a pattern called trauma blight, where symptoms appear randomly and more widespread throughout a tree or orchard because wounds create entry points for bacteria.
What Fire Blight Doesn’t Look Like
A few other problems can mimic fire blight at first glance. Bacterial blast, a different disease, can look similar on apple and pear blossoms, but it rarely damages more than an inch or two of the shoot tip. Fire blight infections typically extend a foot or more down the shoot. Blast-damaged twigs also look light tan and papery, while fire blight twigs are dark brown or black, sunken, and hard. The decisive difference: fire blight produces grayish-brown bacterial ooze during wet weather. Bacterial blast never does.
Frost damage can also blacken blossoms and shoot tips in spring, but frost-damaged tissue dries out uniformly and lacks the progressive wilting, vein darkening, and ooze production that characterize fire blight. If you’re seeing the shepherd’s crook shape, bacterial ooze, or dark streaks running along leaf midveins, fire blight is the much more likely culprit.