Why are the leaves on my austrees turning yellow and falling off?
The Gardener’s Answer
Hello, JoAnn: Austrees are a hybrid willow. They are a cross between a hankow willow (Salix matsudana) and a white willow (Salix alba). At maturity these trees can reach up to 70 feet tall, growing 15 feet in one year. These fast-growing trees develop an extensive root system that requires a lot of moisture. If there is a time when the tree is not receiving the moisture it requires, it can cause the foliage to turn yellow. Like all members of this genus, these trees are susceptible to a wide range of insect and disease problems. They are affected by several different blights and cankers as well as aphids, mites, lace bugs, scale, and sawfly, just to name a few. A severe infestation of any of these insects can damage foliage and cause it to turn yellow. Chlorosis is always in question when foliage begins to yellow. This is a lack of chlorophyll, which can be caused by a few different possibilities including high pH(alkaline soil), poor drainage, and unavailable nutrients. Unfortunately I can only give you possibilities for why your willow is turning yellow. I cannot say for certain what is going on with your particular tree without looking at a sample. For a positive identification you can take a sample to your horticulture agent at your County Cooperative Extension Service. The Barry County Web site is: http://extension.missouri.edu/barry/. The phone number is (417) 847-3161.