Why Are Your Willow Tree's Leaves Crumbling And Falling?


When your willow tree's leaves start turning black and falling to the ground, this is not a good sign. Black, crumbling leaves are a sign of disease in willows. Your tree is most likely suffering from either black canker disease or willow scab. Read on to learn how to tell which is the most likely culprit – and how to treat your tree in either case.

Willow Scab

The effects of willow scab typically present themselves in early spring. The leaves turn black and curl up almost as soon as they sprout. You'll likely notice that the new green branches seem to be more affected than the older-growth branches. If you look closely at the tree's smallest twigs, you may notice that they have black, scabby areas as well.

Willow scab is caused by a fungus called Venturia saliciperda. Thankfully, willow scab is not typically deadly on its own, but leaving your tree untreated will weaken it and make it more susceptible to other illnesses – like black canker – and the combination of multiple infections may be enough to end your tree's life prematurely.  You can fight willow scab by:

  • Cleaning up all fallen leaves promptly. The fungus over-winters and reproduces in the fallen leaves, so eliminating them should prevent your tree from becoming re-infested next year.
  • Having the tree pruned. Heavily infected branches should be removed and burned to be rid of the fungus.

Black Canker

If your tree's leaves did not begin turning black and falling off until the summer, black canker is the likely culprit. If you look at the bark on the branches, you may notice deep black wounds that appear to be oozing. Known as cankers, these are formed by the fungus that causes black canker disease: Glomerella miyabeana.

Black canker is more serious than willow scab and can lead to the dieback of whole branches – and perhaps even the whole tree – if you don't treat it promptly.  A tree care expert can come remove highly infected branches and perhaps pare cankers out of larger branches to prevent them having to be removed. The following spring, the tree can be sprayed with fungicides to prevent it from becoming re-infected. As moist conditions perpetuate the growth of the black canker fungus, effort should be made to prune the tree in a way that allows for plenty of airflow between the branches.

If your willow tree's leaves are turning black and crumbling, don't ignore this symptom. A tree care expert can help you determine whether black canker or willow scab is to blame and can give you some more specialized treatment advice.


15 June 2016

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