white stuff growing on trees - Ask Extension
I live in northern Michigan. I started removing a clump of trees that were ugly and looked like they were dying. As I started cutting each small tru...
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white stuff growing on trees #851181
Asked September 25, 2023, 2:03 PM EDT
I live in northern Michigan. I started removing a clump of trees that were ugly and looked like they were dying. As I started cutting each small trunk, I observed a white styrofoam-looking something growing on the bark of most of them. There were also a few white spots on the underside of some leaves. Can you tell me what this is? Will it spread to my healthy trees? Is there something I need to do?
Cheboygan County Michigan
Expert Response
Hello,
Based on what I see in your images:
Woolly aphids are aphids that produce a covering of fluffy white wax. One of the most common species found in landscapes is the woolly apple aphid. It is most commonly found on crabapple feeding at the base of new shoots. It prefers to suck the sap from roots, branches and twigs of apple, but may also be found on alder, elm, mountain ash, hawthorn, serviceberry, and Pyracantha. Examine trees for bluish-black aphids covered with fluffy white wax on exposed roots, wounds on trunks and branches, and at the bases of new shoots on branches. Other species of woolly aphids include the woolly elm aphid (elm, service berry as alternate host), woolly elm bark aphid (American and slippery elm), beech blight aphid (beech), and woolly alder aphid (alder and silver maple). The white material are secretions from woolly aphids. The aphids will make the leaves sticky and potentially form sooty mildew. Natural enemies in the area will usually feed on some of the aphids. This issue is not related to air circulation. There have been a number of reports of woolly aphids on beech, and we happen to be in a year where aphid populations are higher.
Neem or insecticidal soap are two chemical options. However, it would be tough to get good coverage on your tree. While the leaves may appear a bit unsightly, no chemical treatment is necessary as the tree will survive.
References:
Beech Blight Aphids are Jitterbugging Across Ohio at this link: https://bygl.osu.edu/index.php/node/1871
Woolly Aphids on Trees - University of Maryland Extension: https://extension.umd.edu/resource/woolly-aphids-trees
As for the white spots on the leaves, it’s possible that they are caused by a different issue. Without further information, it’s challenging to pinpoint the exact cause. However, some common causes of white spots on leaves include fungal infections like powdery mildew.
Powderly Mildew - IPM - MSU at this link: https://www.canr.msu.edu/ipm/diseases/powdery_mildew
If you want to get a confirmed diagnosis from the MSU Diagnostic Plant Lab. Please email your digital images prior to bringing or sending physical samples. Images can be sent to <personal data hidden>.
MAKE SURE IN THAT E-MAIL YOU INCLUDE YOUR NAME, ADDRESS, AND PHONE NUMBER!!
Be prepared, the lab may ask for more images - THE LAB WILL LET YOU KNOW IF A SAMPLE NEEDS TO BE SENT - There is a $20-25 dollar fee (if they need a sample sent).
Lab email: <personal data hidden>
Lab phone:<personal data hidden>
Hours of operation: Monday through Friday, from 8:00 AM to 5:00 PM.
PLEASE READ BELOW ON PREPARING YOUR SAMPLE (if the lab needs a sample)
From the lab: Please do not ship samples on Fridays. Due to the current COVID-19 circumstances, please allow additional processing time. They thank you for your patience and understanding.
Every sample must be accompanied by a completed submission form. Please place the form in a separate resealable bag to prevent it from getting damp or soiled. The form is at this link: https://www.canr.msu.edu/pestid/uploads/files/General_Sample_Submission_Form_May2022.pdf
Complete details of submitting a sample are at this link: https://www.canr.msu.edu/pestid/submit-samples/
I hope this helps!
Based on what I see in your images:
Woolly aphids are aphids that produce a covering of fluffy white wax. One of the most common species found in landscapes is the woolly apple aphid. It is most commonly found on crabapple feeding at the base of new shoots. It prefers to suck the sap from roots, branches and twigs of apple, but may also be found on alder, elm, mountain ash, hawthorn, serviceberry, and Pyracantha. Examine trees for bluish-black aphids covered with fluffy white wax on exposed roots, wounds on trunks and branches, and at the bases of new shoots on branches. Other species of woolly aphids include the woolly elm aphid (elm, service berry as alternate host), woolly elm bark aphid (American and slippery elm), beech blight aphid (beech), and woolly alder aphid (alder and silver maple). The white material are secretions from woolly aphids. The aphids will make the leaves sticky and potentially form sooty mildew. Natural enemies in the area will usually feed on some of the aphids. This issue is not related to air circulation. There have been a number of reports of woolly aphids on beech, and we happen to be in a year where aphid populations are higher.
Neem or insecticidal soap are two chemical options. However, it would be tough to get good coverage on your tree. While the leaves may appear a bit unsightly, no chemical treatment is necessary as the tree will survive.
References:
Beech Blight Aphids are Jitterbugging Across Ohio at this link: https://bygl.osu.edu/index.php/node/1871
Woolly Aphids on Trees - University of Maryland Extension: https://extension.umd.edu/resource/woolly-aphids-trees
As for the white spots on the leaves, it’s possible that they are caused by a different issue. Without further information, it’s challenging to pinpoint the exact cause. However, some common causes of white spots on leaves include fungal infections like powdery mildew.
Powderly Mildew - IPM - MSU at this link: https://www.canr.msu.edu/ipm/diseases/powdery_mildew
If you want to get a confirmed diagnosis from the MSU Diagnostic Plant Lab. Please email your digital images prior to bringing or sending physical samples. Images can be sent to <personal data hidden>.
MAKE SURE IN THAT E-MAIL YOU INCLUDE YOUR NAME, ADDRESS, AND PHONE NUMBER!!
Be prepared, the lab may ask for more images - THE LAB WILL LET YOU KNOW IF A SAMPLE NEEDS TO BE SENT - There is a $20-25 dollar fee (if they need a sample sent).
Lab email: <personal data hidden>
Lab phone:<personal data hidden>
Hours of operation: Monday through Friday, from 8:00 AM to 5:00 PM.
PLEASE READ BELOW ON PREPARING YOUR SAMPLE (if the lab needs a sample)
From the lab: Please do not ship samples on Fridays. Due to the current COVID-19 circumstances, please allow additional processing time. They thank you for your patience and understanding.
Every sample must be accompanied by a completed submission form. Please place the form in a separate resealable bag to prevent it from getting damp or soiled. The form is at this link: https://www.canr.msu.edu/pestid/uploads/files/General_Sample_Submission_Form_May2022.pdf
Complete details of submitting a sample are at this link: https://www.canr.msu.edu/pestid/submit-samples/
I hope this helps!
Thank you for your quick, thorough response. That is very helpful.
You are welcome! Have a great day!
