Trees - Diseases
Back to Trees

  (March) My husband and I are desperate! We have two beautiful crabapple trees in our front yard, and every year experience the same problem with them. They come out just fine in the spring and bloom. Then about four to six weeks later, the leaves begin to turn black and drop off. They struggle and eventually produce more leaves, but they also turn black drop off. We watch carefully for these, and spray quickly when they appear. We have also used some fertilizer stakes. Would you give us some advice as to this problem?

  It sounds to me like your crabapples are suffering from fireblight. Fireblight is a bacterial disease that is spread during the bloom season by the bees as they are pollinating the trees. It appears shortly after bloom and will look like the tree has been hit with a fire-the leaves will turn black and scorched looking. The ends of the branches will typically get a shepherds crook--or a wilted tip. Once you get the problem, there is no control, except cutting out the damaged wood six to eight inches beneath where damage is visible. The only possible control measure is to spray with streptomycin, or Agri-strep, or fireblight spray, when the trees are in bloom. Spray every three to five days during bloom and hope for the best. Even with spraying, if you have a highly susceptible tree, and conditions are good for fireblight, you may still get it. If you still see black appearing this season, prune out the infected limbs, six to eight inches beneath where the damage has occurred, sterilize your pruning shears in between each cut with a Clorox solution. Once the temperatures warm up to 80 - 85 degrees, the spread of this disease should stop for the season.

  (May) I have two large Bradford pear trees that are approximately ten years old. They have developed dead branches and shriveled leaves which I have been told is fireblight. It would be almost impossible to trim the tops of these trees but I need some guidance. Any help will be appreciated.

  If it truly is fireblight, which we have seen on the ornamental pears in recent years, pruning is needed. Fireblight looks like something burned the tips of the branches, and there is usually a shepherd's crook appearance where the tips flag down. If you leave the diseased branches on the tree the bacteria will spread through the limb, causing even more loss. Once the temperatures warm up the disease will stop for this season, but the disease will still be present in the wood. It will also begin to ooze bacteria from the damaged limbs next spring, which can also spread the disease. Removing the limbs 8-10 inches beneath where you see visible damage and sterilizing between cuts is your only recourse. You might invest in a pole pruner to make the job manageable, or hire a tree service. Sprays now are totally ineffective.

  (May) I was walking in my yard following the recent rains and found my cedar tree covered in orange blobs. What in the world is this, and is it going to hurt my cedar tree?

  The orange blobs, which form orange gelatinous tentacles are the fruiting bodies of cedar‑apple rust. This disease has two host plants, the Eastern red cedar, and the apple, crabapple and hawthorne trees. The orange blobs will disperse their fruiting spores which can infest the apple trees, and then they will become hard brown balls or galls on the cedar trees. Usually the damage is minimal on the cedars, but heavy infestations can defoliate an apple tree. If you are growing susceptible apples or crabapples, you should be using preventative fungicide sprays weekly when the foliage begins to emerge through mid May. Spraying the cedar trees is rarely recommended and too late now anyway.

Back to Trees