The blighted leaves, fruits and flowers are black and shriveled and look as though they were scorched with fire. They remain clinging to the shoots. Shoots often have a bent, drooped tip resembling a shepherd's crook.
Bacteria generally cause blights during wet weather in early spring when buds are breaking.
Cool spring temperatures favor some blights and warm temperatures favor others. Fire blight of crabapples, for example, is favored by warm springs, and bacterial blight of lilac is favored by cool springs. In wet spring weather, cankers formed during previous infections ooze droplets of bacteria. The bacteria are splashed by rain and blown about as mists, or insects may visit the attractive ooze and carry it about. In lilac bacterial blight, typical blight symptoms may occur on new growth.