Question
Our 13yr old curly willow has been dropping yellowed leaves
this summer.  We've notice the plants below are being affected
by these leaves.  Is this a fungus or some other disease?
Do we need to remove the tree?  This has happened over the
last few years....every summer.  We've tried washing it down
with soapy solution, but this tree is pretty tall.

Would appreciate any suggestions.

Thank you.


Answer
The first thing I would suspect would be lack of water. willows need a great deal of water or they will drop leaves. Water with once a week with 1 inch of water-place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop.

Other possibilities would be borer damage --you should see holes in the bark of the trunk where the insect has entered. If you see the holes spray the trunk with an insecticide called Merit this will kill the borers in the trunk.

There are a few diseases that will infect willow leaves but these start as spots on the leaves and over time may kill the entire leaf but this does not sound like what you have.

Since other plant under the tree are effected I would lean toward water--the tree is taking up most of the water and the plants under it are not getting their share.