Disease on Tree - Ask Extension
I have a tree with dying/diseased leaves. I do not know what type of tree it is. It seems this could be a fungus as my vegetable garden is turning col...
Knowledgebase
Disease on Tree #875083
Asked June 28, 2024, 11:01 AM EDT
I have a tree with dying/diseased leaves. I do not know what type of tree it is. It seems this could be a fungus as my vegetable garden is turning colors as well. This tree drips sticky sap off of its leaves during the spring which attracts many bees. It is really hard to take pictures of it because there are no branches close to the ground. I hope these pictures of the tree that leans over the roof will help you see the damage to all the leaves and help you to identify it.
Eaton County Michigan
Expert Response
Hi Sue, Thank you for your inquiry. That sticky goo dripping from your tree is called honeydew—but it’s not so sweet.
Honeydew is the waste aphids and several other sap-sucking insects (such as soft scale, leaf hoppers and mealybugs) leave behind after snacking on sap. Along with tree leaves, it can drip onto branches, patios, driveways or any areas under the canopy. Honeydew does attract bees and other flying insects, as well as ants. Often a black, sooty fungal mold develops on the leaves. This mold is unsightly but it does virtually no harm to the plant.
During dry periods, aphid populations and their honeydew production typically increase on foliage undergoing moisture stress. In addition, under dry conditions, less rain is available to remove or dilute honeydew concentrations suitable for sooty mold growth on leaves and other surfaces.
Aphids actually don’t do much damage to healthy, mature trees. Aphids can be controlled simply with sharp sprays of water, although reaching to the top of that tree would be difficult. A strong gust of water knocks aphids right off, and once they fall, it’s not likely they’ll find their way back.
Horticultural oil is extremely effective in controlling aphids, but
only if you thoroughly treat the tree. Apply the oil in the dormant
season to kill any overwintering eggs. If needed, you can also use a lower rate of the oil during the growing season as well. Again, due to the size of your tree, spraying likely isn't possible.
There are insecticides that can be applied to the soil below the tree at the roots to systemically treat for aphids. That's a job for professionals.
There is a possibility the aphids may not be so numerous next year. But...if this tree is valuable to you and you cannot tolerate the level of honeydew you are experiencing, the best thing to do at this point for diagnosing and treating your tree is to consult a certified arborist. An arborist is a certified and generally insured expert in trees and their problems. He or she can examine your tree and make recommendations regarding the health of the tree, any needed judicial pruning, and whether or not (in his opinion) it should be removed. Hiring a certified arborist will ensure that you are getting a knowledgeable and qualified tree specialist. You can find a certified arborist in your area here:
http://www.treesaregood.org/
Honeydew is the waste aphids and several other sap-sucking insects (such as soft scale, leaf hoppers and mealybugs) leave behind after snacking on sap. Along with tree leaves, it can drip onto branches, patios, driveways or any areas under the canopy. Honeydew does attract bees and other flying insects, as well as ants. Often a black, sooty fungal mold develops on the leaves. This mold is unsightly but it does virtually no harm to the plant.
During dry periods, aphid populations and their honeydew production typically increase on foliage undergoing moisture stress. In addition, under dry conditions, less rain is available to remove or dilute honeydew concentrations suitable for sooty mold growth on leaves and other surfaces.
Aphids actually don’t do much damage to healthy, mature trees. Aphids can be controlled simply with sharp sprays of water, although reaching to the top of that tree would be difficult. A strong gust of water knocks aphids right off, and once they fall, it’s not likely they’ll find their way back.
Horticultural oil is extremely effective in controlling aphids, but
only if you thoroughly treat the tree. Apply the oil in the dormant
season to kill any overwintering eggs. If needed, you can also use a lower rate of the oil during the growing season as well. Again, due to the size of your tree, spraying likely isn't possible.
There are insecticides that can be applied to the soil below the tree at the roots to systemically treat for aphids. That's a job for professionals.
There is a possibility the aphids may not be so numerous next year. But...if this tree is valuable to you and you cannot tolerate the level of honeydew you are experiencing, the best thing to do at this point for diagnosing and treating your tree is to consult a certified arborist. An arborist is a certified and generally insured expert in trees and their problems. He or she can examine your tree and make recommendations regarding the health of the tree, any needed judicial pruning, and whether or not (in his opinion) it should be removed. Hiring a certified arborist will ensure that you are getting a knowledgeable and qualified tree specialist. You can find a certified arborist in your area here:
http://www.treesaregood.org/
Click on "Find an Arborist" at the top of the page; then click on United States from the pull-down menu. Then enter your State and City. This should bring up a list of certified arborists nearest to you. Or you may be able to locate one under "Tree Services" in your local Yellow Pages.
Thank you for the very detailed reply.
That is very interesting about the aphids, however, they have never killed the leaves before. This dripping sticky stuff happens every year but I've never had all the dead leaves all over the tree before. What do you think that is?
On Mon, Jul 1, 2024 at 12:29 PM, Ask Extension<<personal data hidden>> wrote:
It is possible that your tree is suffering from more than one pest or disease. I cannot ascertain what killed the brown leaf your image shows. Dying and falling leaves can be caused by drought stress, compacted roots, lack of nutrients and several other problems. Your best course of action ... if you value this tree ... is to have an arborist take a look at it on-site. I wish I had a better answer for you, but diagnosing tree problems is not always possible by looking at pictures.
