Problem with variegated willow

Question: This was a heathy tree until last year but now the leaves are drying and dropping

responder: Jacki D., Master Gardener Diagnostician Volunteer (Washington, Multnomah and Clackamas Counties) Oregon State University Extension Service Volunteer Metro Master Gardeners (http://metromastergardeners.org/) Replied September 13, 2024, 8:54 PM EDT
response: Willow trees are known for having less-than long lives. They grow fast and have fairly weak wood and there’s numerous problems, such as cankers and pests. It is possible we won’t identify the exact trouble with your tree, but I’m happy to troubleshoot it with you. I’ll attach some references at the end, for you to study. First, because these willows like a moist, rich, well draining soil, how is the soil moisture? If you spade some soil, how far down is it moist? Another measuring option is pushing a screwdriver down, and noting the depth where it hits the hard dry soil. Examine the leaves and bark for insects and cankers. If you are unfamiliar with scale insects, look those up online and see if your plant has those. Lastly, provide a view from more distance, including the surrounding plantings. Sometimes I find a clue there, such as new construction damaging roots, or a neighboring tree out-competing the declining plant for water and sun. See Common diseases of willow for more information. This prior Q&A has a thoughtful answer about challenges growing this willow in the Midwest, and might have applications for Oregon also. This data page from NCSU is good overall information, and mentions regular hard pruning to force colorful new growth. Some common pests of willow are listed here. I look forward to your reply.

responder: The Question Asker Replied September 15, 2024, 11:01 PM EDT
response: Dear JackiThank you for all your very interesting information and references. Unfortunately I cannot trust my skills and judgement regarding the moisture of the soil. I tried to spade some soil but I soon met the roots and stoped for fear of damaging them. I might ask for some help from a neighbor for that. The gap between the willow and the Rhodo to the left is due to the pruning of dry branches of the willow in that side all summer long. I did not find any insects but I took new photos and some problems are apparent.I have not been using any fertilizer nor any pesticide. I don’t know what is the overhead watering that should be avoided.  I have irrigation with sprinkles on the ground but they send water up. Could you advice on how many minutes and how often I should program the irrigation for the willow? It is in the same zone system as the Rhodos. Thank you so much for your help!Carmen On Sep 13, 2024, at 5:54 PM, Ask Extension <<personal data hidden>> wrote:

responder: Jacki D., Master Gardener Diagnostician Volunteer (Washington, Multnomah and Clackamas Counties) Oregon State University Extension Service Volunteer Metro Master Gardeners (http://metromastergardeners.org/) Replied September 16, 2024, 6:35 PM EDT
response: Please provide a clear photo of the bark that is bare of leaves. (In the third photo.) Looking closely, are those marks things that rub off? How much of the twiggy bark in the plant has those, meaning is it in one section? or all over? Are those scale insects?  Here is a page with photos of different types of scale. The dried tips of leaves can indicate a water shortage in the leaf, but the cause can be due to disease or under-watering. Are you able to determine the depth of moisture using the screwdriver method? Maybe share a photo of the soil under your willow. When you did dig, was it moist for as far as you did go down?  I would expect the willow to need more water than the maple or Rhododendron next to it.