Diseases/pests on American Linden trees - Ask Extension
I have two mature American Linden’s 30 to 40 feet tall. One has had blotchy leaves all season. The other seems to now have an infestation causing la...
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Diseases/pests on American Linden trees #919835
Asked October 13, 2025, 10:26 AM EDT
I have two mature American Linden’s 30 to 40 feet tall. One has had blotchy leaves all season. The other seems to now have an infestation causing lace like destruction on the leaves.
Adams County Colorado
Expert Response
Jay,
It looks as though you've got several issues going on at the moment.
1. lacey leaves -- this is consistent with the feeding patterns from Japanese Beetle. See this document for control options (control both the larval/turf stage and the adult stage will reduce populations more than one or the other. https://extension.colostate.edu/resource/japanese-beetle/
2. White dusty material appears to be powdery mildew which rarely harms the tree. It is often a sign of local high humidity so pruning for air movement and removing leaves in fall can help with re-infestation in future years.
3. the browning on the tips/edges is called scorch and a sign that the tree has not been able to transport sufficient water from the soil through the leaves. Lindens are particularly prone to this in hot and dry Colorado summers and while increasing water sometimes helps, it often occurs anyway.
I hope that's helpful and let me know if you have additional question
It looks as though you've got several issues going on at the moment.
1. lacey leaves -- this is consistent with the feeding patterns from Japanese Beetle. See this document for control options (control both the larval/turf stage and the adult stage will reduce populations more than one or the other. https://extension.colostate.edu/resource/japanese-beetle/
2. White dusty material appears to be powdery mildew which rarely harms the tree. It is often a sign of local high humidity so pruning for air movement and removing leaves in fall can help with re-infestation in future years.
3. the browning on the tips/edges is called scorch and a sign that the tree has not been able to transport sufficient water from the soil through the leaves. Lindens are particularly prone to this in hot and dry Colorado summers and while increasing water sometimes helps, it often occurs anyway.
I hope that's helpful and let me know if you have additional question
Thank you for your response. I have a couple of other questions regarding a mature ponderosa pine whose rigorous new candles dry up and die every year overwinter. This has caused stunting, which is actually a plus. Any suggestions? Do you think it’s color is right?
Sent from my iPhone
Finally, do you have any ideas how to limit the Japanese beetle epidemic we experience every summer?
Sent from my iPhone
On Oct 13, 2025, at 12:53 PM, Ask Extension wrote:
Jay,
Can you provide pictures of these candles as they grow and then drop off? There are some pests and some abiotic causes that could be leading to this as an issue. The color of the tree overall looks good from your picture.
Regarding Japanese Beetle, treating your lawn with Acelepryn (GrubEx) listed in my previous reply will help, especially if you get some of your local neighborhood to do it as well. Adults can be hand-picked daily by dropping them into a container with soapy water. Each adult removed from can be 40-50 beetles you don't have next year. That same resource has several treatment options for adults as well, be sure to read the label of any product you use to ensure you're using it appropriately to reduce environmental impacts.
Happy to chat more if you have additional questions.
~ Cassey
Can you provide pictures of these candles as they grow and then drop off? There are some pests and some abiotic causes that could be leading to this as an issue. The color of the tree overall looks good from your picture.
Regarding Japanese Beetle, treating your lawn with Acelepryn (GrubEx) listed in my previous reply will help, especially if you get some of your local neighborhood to do it as well. Adults can be hand-picked daily by dropping them into a container with soapy water. Each adult removed from can be 40-50 beetles you don't have next year. That same resource has several treatment options for adults as well, be sure to read the label of any product you use to ensure you're using it appropriately to reduce environmental impacts.
Happy to chat more if you have additional questions.
~ Cassey
