Q. My crabapple tree
bloomed beautifully this spring, but some of the blooms seemed to
die. Now I'm noticing that some of the branches look like they are
dying at the tips. Can you tell me what might be wrong, and what I
can do to help my crabapple tree?
Judging by your description and the branch sample you sent, your
crabapple (Malus spp.) is suffering from a common disease known as fire blight. This bacterial disease, caused by the bacterium
Erwinia amylovora, affects many plants in the rose family, including
apple, cotoneaster, crabapple, hawthorns, pears, pyracantha and
serviceberries. Fire blight enters susceptible plants through wounds
and through natural openings, such as the nectaries of flowers.
Spread of the disease
Bees and other pollinators commonly spread the disease as they work
the flowers. The development of fire blight is favored by warm, wet
Initial symptoms include the sudden wilting and shriveling of
individual flowers or entire flower clusters, as happened with your
tree. Flowers typically turn brown, then black, and remain attached
to the tree after they die. As the infection spreads from flower
clusters down the twig, leaves begin to die. They also turn
brown-black and remain on the tree.
Crabapple creating a fantastic flower show
plants often escape the initial blossom infection during cool spring
weather because temperatures are not warm enough for the disease to
develop. In that case, the first symptom you notice may be shoot
blight. Succulent new growth wilts and soon becomes withered and
brown. It looks as though the tree has been singed by fire; hence
the name fire blight. The tips of affected shoots curl over into a
characteristic shepherd's crook shape. Scattered shoots on the tree
may be infected simultaneously, giving the entire tree a scorched
appearance. On close examination you should be able to see small,
slightly sunken reddish-brown or black cankers where the scorching
stops or where the affected shoot attaches to a larger branch.
During warm, wet spring weather, you may notice liquid oozing from
older cankers that has an unpleasant odor.
As this ooze drips onto lower parts of the tree, the bacteria can
gain entry to the trunk through natural openings in the bark known
as lenticels. (Lenticels lined up in horizontal patterns give cherry
bark its characteristic appearance). The disease can also enter
through pruning wounds, storm damage, or through damage from lawn
mowers or weed whackers. Infections low on the tree, on the root
collar or trunk are often fatal.
Crabapple Fire Blight
suckers and water sprouts.
infected branches in dry weather during dormancy.
infected branches 4-inches or more below the canker.
resistant crabapple cultivars.
infected branches is the primary control for fire blight. This
should only be done during dry weather when the tree is dormant.
Older recommendations called for pruning infected branches whenever
they appeared, but recent research indicates that pruning during the
growing season results in more rapid spread of the disease, even
when pruning tools were properly sterilized between cuts.
Remove infected branches at least 4 inches below the base of a
canker. Disinfect pruners with a 70 percent alcohol solution between
cuts to reduce spread of the disease. Avoid pruning or working
around infected plants when the weather is warm and wet. Send
infected prunings out with the trash or burn them rather than
Avoid excessive fertilization that promotes a lot of succulent
growth, which is most susceptible to infection. Also, remove root
suckers and water sprouts, as these are very succulent and create a
perfect point of entry for the bacteria. Root suckers are upright
shoots that grow from the base of the tree. Water sprouts are
upright shoots that grow straight up from branches, often as a
result of old pruning cuts.
The best way to treat fire blight is to minimize the chance of your
tree getting it by growing resistant cultivars of crabapples. These
include 'Adams,' 'Callaway,' 'David,' 'Dolgo,' 'Harvest Gold,'
'Indian Summer,' 'Jewelberry,' 'Liset,' 'Profusion,' 'Red Baron,'
'Selkirk' and 'Sentinel.' Although resistance is not immunity, it
helps to start with a plant that is not highly susceptible.
Fruit Tree Care
Flowering crabapple photos