aspen producing sap and brown spots on leaves - Ask Extension
Hi, I am in Steamboat Springs and have an aspen whose leaves are producing a shiny sap and some have brown spots on them.How can I get advice on how t...
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aspen producing sap and brown spots on leaves #468072
Asked July 06, 2018, 12:19 PM EDT
Hi, I am in Steamboat Springs and have an aspen whose leaves are producing a shiny sap and some have brown spots on them.
How can I get advice on how to best treat this problem? Can it spread to neighboring aspen?
Cristina
How can I get advice on how to best treat this problem? Can it spread to neighboring aspen?
Cristina
Routt County Colorado
Expert Response
Hi Christina-
Are the leaves 'spotted' with stick residue? If so, and I think that's what you're describing, then you have aphids on your tree. This is very common here. Aphids use their little mouthparts to suck phloem out of tree leaves and the residue you see is actually their excrement. WOW! It's called 'honeydew' and it gets all over whatever is under the tree: sidewalks, decks, cars, etc. And it gets all over the lower leaves of the tree. Simply getting a strong jet on your hose and trying to spray off the upper reaches of the tree can help knock off the aphids and bring some relief for a few days, then repeat. Do this in the cooler part of the day, like early morning or late evening.
The brown spotting can be several things. We usually see a lot of marsonina spot on our aspen, but it hasn't been bad this year since we've had little rain. Marsonina is a spore that spreads a lot when it's wet and causes a brown spot with a yellow/ gold halo around it. Again, if that's what you're seeing, not anything to worry about and typical for aspen around here.
If you think you're seeing something significantly different than what I've explained, try to take some pictures of the leaves up close and send them back to me by way of reply.
Are the leaves 'spotted' with stick residue? If so, and I think that's what you're describing, then you have aphids on your tree. This is very common here. Aphids use their little mouthparts to suck phloem out of tree leaves and the residue you see is actually their excrement. WOW! It's called 'honeydew' and it gets all over whatever is under the tree: sidewalks, decks, cars, etc. And it gets all over the lower leaves of the tree. Simply getting a strong jet on your hose and trying to spray off the upper reaches of the tree can help knock off the aphids and bring some relief for a few days, then repeat. Do this in the cooler part of the day, like early morning or late evening.
The brown spotting can be several things. We usually see a lot of marsonina spot on our aspen, but it hasn't been bad this year since we've had little rain. Marsonina is a spore that spreads a lot when it's wet and causes a brown spot with a yellow/ gold halo around it. Again, if that's what you're seeing, not anything to worry about and typical for aspen around here.
If you think you're seeing something significantly different than what I've explained, try to take some pictures of the leaves up close and send them back to me by way of reply.
Thank you for your quick reply. I think I can see the aphids on the leaves!! I am sending some pictures. I sprayed with water today but it is a very tall tree! Are the aphids harmful? Would they kill the tree or are they just an annoyance? Will just water do the trick?
Thank you for your quick reply. I think I can see the aphids on the leaves!! I am sending some pictures. I sprayed with water today but it is a very tall tree! Are the aphids harmful? Would they kill the tree or are they just an annoyance? Will just water do the trick?
Looks like we have a winner! Just water will do the trick as aphids are fairly simple, defenseless creatures. You will continue to have a ton, especially as the reproduce amazingly fast, but at least the symptoms (ie: honeydew) will be reduced. Spray every few days for best control of the symptoms.
Aphids are causing the tree some stress as they suck the phloem out of the leaves, but if you can irrigate the tree some, it should overcome any issues very easily. Water the area near the drip line; if you have a lawn or garden under this area and water it, then you’re already taking care of the tree, too. In general, however, the aphids should not cause long-term damage to the tree and are more of an annoyance.
Let me know if you have other questions. Otherwise, good luck!
Thank you!
Thank you!
You’re welcome! Stop by our local office sometime if you’d like to discuss further. First floor of the Routt County Courthouse Annex, northwest corner.
