Cottonwood Tree leaf disease - Ask Extension
The 35 y.o. Cottonwood Tree I have in my yard is dropping leaves. Much more than it usually does in the heat of the Texas summer. The leafs have som...
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Cottonwood Tree leaf disease #349992
Asked August 04, 2016, 1:15 PM EDT
The 35 y.o. Cottonwood Tree I have in my yard is dropping leaves. Much more than it usually does in the heat of the Texas summer. The leafs have some sort of white colored powdery film on them at the junction of the stem and the body of the leaf. I have attached a picture of what I am seeing. Any idea what this may be?
Tarrant County Texas
Expert Response
Good morning,
It looks like you have submitted this question three times, so I pulled them all from the unanswered pile, and because we have to answer each one, you'll see this same response cut and pasted on each questions.
Cottonwood is indeed susceptible to powdery mildew. One key to diagnosis is that you will find the fungal growth on both the upper and lower surfaces of the affected leaves. Here is a link to the Texas Plant Disease Handbo0k information about cottonwood diseases: https://plantdiseasehandbook.tamu.edu/landscaping/trees/cottonwood-and-poplar/ The TPDD lab can determine if you do have a leaf disease. If you wish to submit a sample to them, click on the page above on the far right side under resources. Instructions and submission forms are available there.
The fact that you only see the powdery material at the base of the leaves and that you see it on all the leaves would not point to a disease so much as to an abiotic problem. If I had to guess why any tree was losing leaves right now, I would guess water related stress. It is so hot and dry that most large trees are shedding some leaves because they can't take up enough water to keep them all hydrated. A mature tree such as yours could need up to 250 gallons of water per day this time of year. You may need to supplement the water for this tree. A soaker hose is a pretty good and simple way to do this. Water until you can easily sink an 8 inch screwdriver into the soil around the tree
It is also possible that this tree may be nearing the end of its natural lifespan. Cottonwoods, like other fast growing trees typically live only about 50 years. Because this one is so large and so close to a building, you may want to have a certified arborist evaluate it periodically.
It looks like you have submitted this question three times, so I pulled them all from the unanswered pile, and because we have to answer each one, you'll see this same response cut and pasted on each questions.
Cottonwood is indeed susceptible to powdery mildew. One key to diagnosis is that you will find the fungal growth on both the upper and lower surfaces of the affected leaves. Here is a link to the Texas Plant Disease Handbo0k information about cottonwood diseases: https://plantdiseasehandbook.tamu.edu/landscaping/trees/cottonwood-and-poplar/ The TPDD lab can determine if you do have a leaf disease. If you wish to submit a sample to them, click on the page above on the far right side under resources. Instructions and submission forms are available there.
The fact that you only see the powdery material at the base of the leaves and that you see it on all the leaves would not point to a disease so much as to an abiotic problem. If I had to guess why any tree was losing leaves right now, I would guess water related stress. It is so hot and dry that most large trees are shedding some leaves because they can't take up enough water to keep them all hydrated. A mature tree such as yours could need up to 250 gallons of water per day this time of year. You may need to supplement the water for this tree. A soaker hose is a pretty good and simple way to do this. Water until you can easily sink an 8 inch screwdriver into the soil around the tree
It is also possible that this tree may be nearing the end of its natural lifespan. Cottonwoods, like other fast growing trees typically live only about 50 years. Because this one is so large and so close to a building, you may want to have a certified arborist evaluate it periodically.
