sudden leaf drop on ash tree

Question: Leaves on a very large, about 50 year old ash tree, are suddenly drying up and falling off. Tree has been treated for Emerald ash borer every year, for many years. I see no sign of bugs or disease. Major pruning was done last Fall. I suspect it is the very high temperatures we have been experiencing the past couple of weeks. I am not concerned with the premature loss of leaves, but don't want to lose the tree. I'm not sure they will tell you anything, but 2 pictures are attached. The only water the trees have been getting is from soaking lawn watering 3 times a week. Is root watering recommended? Anything else?

responder: Jeff C, Master Gardener Volunteer Replied August 07, 2024, 7:36 PM EDT
response: Hello there and thank you for using Ask Extension.   Sorry to hear about your ash tree. The photos are helpful, but based upon them alone, it is difficult to make a diagnosis.   Leaf drop on ashes can be due to a variety of issues.  Here they are.  1. Naturally dropping leaves from the canopy due to insufficient water.  This will happen after a wet spring and then a prolonged dry period.  It sounds like your tree is getting enough water, but could be a factor.  2. Ash anthracnose:  a fungal disease.  It tends to be primarily cosmetic, but can be fatal if a tree is already stressed.  The leaves have irregular shaped brown spots.  3. Vascular disease: Verticillium wilt can also cause leaf drop.  The bacteria gets inside the tree and basically cuts off the flow of nutrients to the tree which causes wilting.  4. Girdling roots:  This is when the trees roots circle around the tree and don't grow away from the trunk.  I don't think this is a possibility since your tree is so old.  This usually shows up after 10 - 12 years.   5. Cankers:  This is also a fungal disease that penetrates the bark of the tree.  It can be on a limb or on the main trunk.  If you see a sunken wound on the tree, this could be a canker.  6. Pesticides:  Pesticides can effect trees!  If the leaves are cupped this would be an indication of pesticide damage.    To help me narrow down the possibilities, could you please send me some more photos.  I would like to see some photos of the base of the tree, a close up and one further out so that I can see how it sits in the landscape. Also, please send me some photos of the leaves that have fallen.    I have some additional questions.   1. Does the soil around the tree seem moist? Try putting a flat head screw driver into the soil.  If it is hard to insert, the soil is too dry.  2. From the photo, it appears that the whole tree is affected.  Is this accurate or is just one side or one limb or just the inner leaves or just the outermost leaves? 3. Take a look at the main trunk for cankers.  Do you see anything that could be a canker?  If so, send me a photo.  4. Have any pesticides been applied in the vicinity of the tree, such as a weed killer? 5. Have you fertilized the area around the tree?  If so, with what?   6. Finally, tell me about your EAB treatments.  What are you using?    This PDF from Iowa State describes the above issues plus more.  Take a look at it.  However, some of the problems mentioned in the PDF don't apply to Colorado, so just look at the issues I mention above.  https://store.extension.iastate.edu/product/Common-Problems-of-Ash-Trees    Sorry for all the questions.  I look forward to hearing back from you.

responder: The Question Asker Replied August 10, 2024, 5:20 PM EDT
response: Jeff-   Thank you so much for the detailed help. I apologize for the delay, but I am still waiting for an answer from SavATree as to the exact products used for EAB treatment and fertilization.  I will pass on that info as soon as I get it.  The rest of the answers are inserted below, in red, following each of your questions.   - - Henry Reckler The Question Asker Replied August 10, 2024, 5:20 PM EDT

responder: Jeff C, Master Gardener Volunteer Replied August 10, 2024, 7:42 PM EDT
response: Hi Henry,   The answers in red did not go through.  I think this system does not allow for editing a previous email.  Can you write the number of the question and the answer?  Sorry for the antiquated system we have.

responder: The Question Asker Replied August 10, 2024, 11:51 PM EDT
response: No problem. Will do so sometime tomorrow.       - - Henry Reckler The Question Asker Replied August 10, 2024, 11:51 PM EDTGreat.  Please remember to the send the photos I requested too.   thanksJeff C, Master Gardener Volunteer Replied August 13, 2024, 6:39 PM EDTJeff- Thank you so much for the detailed help. I apologize for the initial delay, and the subsequent delay (caused by an unplanned trip to the ER + 2 days in the hospital). I am home, and fine, but still waiting for an answer from SavATree as to the exact products used for EAB treatment and fertilization. I will pass on that info as soon as I get it. Here are the rest of the answers to your questions, numbered as you suggested. I could easily put a four inch long flat head screw driver fully into the soil all the way around, very close to the base of the tree and further out. The soil in the area generally is quite compacted but at the same time, there has been an overabundance of rain the past few days after a prolonged high temperatures for many days before that.  You are correct. None of the branches is stripped of its leaves, but the whole tree is affected. I see nothing of the sort. No. The lawn was last fertilized in mid-July. I am still waiting for info as to the specific product used. It has been done by soil injection. The last time was in June. I am still waiting for info as to the specific product use.  I appreciate your gracious help. In case it is pertinent, I thought I would mention a few other things. There is another ash tree about 30 yards away, planted at the same time. It is untouched by this problem. I am sending a picture so you can see. While the two trees are in lawn areas, the sprinkler system zone where the affected tree is had an undetected leak for a large part of the summer of 2022, with the result that the root system on one side likely received its regular amount of water, and on the other side, either significantly more, or significantly less than usual. I do not know where the water for that zone ended up below ground until the leak in the system was fixed. In any case, it has been working perfectly since.  Some photos are attached.  Apparently there is a limit per upload.  I will try sending rest separately.The Question Asker Replied August 13, 2024, 7:38 PM EDTAdditional pictures.The Question Asker Replied August 13, 2024, 9:36 PM EDTLast three pictures.The Question Asker Replied August 13, 2024, 9:37 PM EDTHello again, Henry.    Thank you for the additional information and the photos.  Based upon your photos and information, I do not think your tree is in dire straights.    Your tree does not appear to suffering from a disease or pest.  The tree also seems to have a very full canopy.  If you lose more than 30% of the leaves from early leaf drop, that could be a symptom that something more serious is going on.  I suspect the tree is just adapting to the hot dry months we had this summer.    Here are some recommendations:  1. I would suggest adding some wood chip mulch around the base of each ash tree.  Look at page 245-5 of this pdf.  You only need to put about an inch depth around the base of the tree and only out about 2 feet.  Leave some space between the actual tree trunk and the mulch.  Here's the pdf:   https://cmg.extension.colostate.edu/Gardennotes/245.pdf  2. Be sure to water your tree, in fact the entire landscape if we have a dry winter.  Trees need about an inch of water every month during the fall and winter.  You'll need to keep track of the snowfall and estimate how much water it would melt down to.  Here's a fact sheet on fall and winter watering.   https://extension.colostate.edu/topic-areas/yard-garden/fall-and-winter-watering-7-211/  3.  No need to add additional water during the summer.  No need to root water or fertilize the tree.  We had a pretty wet May, and the tree probably put on more leaves than it could handle.  Based upon the appearance of your landscape, the tree is getting enough water.    4. No need to send me the EAB treatment.  Here's our fact sheet on EAB treatment.  Take a look at the table at the bottom.  It lists several treatments, one of which Save-a-Tree is probably using.  However, many people prefer to use a pesticide that can be applied every two years rather than every year.  You may want to ask them about that.  https://extension.colostate.edu/topic-areas/insects/insecticides-used-to-control-emerald-ash-borer-on-residential-shade-trees-5-626/  Let me know if you have further questions.  Enjoy your tree!      Jeff C, Master Gardener Volunteer Replied August 14, 2024, 2:07 PM EDT Jeff, thank you.  Your expertise, and kind and generous efforts are very much appreciated.   - - Henry Reckler The Question Asker Replied August 15, 2024, 1:10 AM EDTYou're welcome.  Jeff C, Master Gardener Volunteer Replied August 16, 2024, 12:59 PM EDT

responder: Jeff C, Master Gardener Volunteer Replied August 13, 2024, 6:39 PM EDT
response: Great.  Please remember to the send the photos I requested too.   thanks

responder: The Question Asker Replied August 13, 2024, 7:38 PM EDT
response: Jeff- Thank you so much for the detailed help. I apologize for the initial delay, and the subsequent delay (caused by an unplanned trip to the ER + 2 days in the hospital). I am home, and fine, but still waiting for an answer from SavATree as to the exact products used for EAB treatment and fertilization. I will pass on that info as soon as I get it. Here are the rest of the answers to your questions, numbered as you suggested. I could easily put a four inch long flat head screw driver fully into the soil all the way around, very close to the base of the tree and further out. The soil in the area generally is quite compacted but at the same time, there has been an overabundance of rain the past few days after a prolonged high temperatures for many days before that.  You are correct. None of the branches is stripped of its leaves, but the whole tree is affected. I see nothing of the sort. No. The lawn was last fertilized in mid-July. I am still waiting for info as to the specific product used. It has been done by soil injection. The last time was in June. I am still waiting for info as to the specific product use.  I appreciate your gracious help. In case it is pertinent, I thought I would mention a few other things. There is another ash tree about 30 yards away, planted at the same time. It is untouched by this problem. I am sending a picture so you can see. While the two trees are in lawn areas, the sprinkler system zone where the affected tree is had an undetected leak for a large part of the summer of 2022, with the result that the root system on one side likely received its regular amount of water, and on the other side, either significantly more, or significantly less than usual. I do not know where the water for that zone ended up below ground until the leak in the system was fixed. In any case, it has been working perfectly since.  Some photos are attached.  Apparently there is a limit per upload.  I will try sending rest separately.

responder: The Question Asker Replied August 13, 2024, 9:36 PM EDT
response: Additional pictures.

responder: The Question Asker Replied August 13, 2024, 9:37 PM EDT
response: Last three pictures.

responder: Jeff C, Master Gardener Volunteer Replied August 14, 2024, 2:07 PM EDT
response: Hello again, Henry.    Thank you for the additional information and the photos.  Based upon your photos and information, I do not think your tree is in dire straights.    Your tree does not appear to suffering from a disease or pest.  The tree also seems to have a very full canopy.  If you lose more than 30% of the leaves from early leaf drop, that could be a symptom that something more serious is going on.  I suspect the tree is just adapting to the hot dry months we had this summer.    Here are some recommendations:  1. I would suggest adding some wood chip mulch around the base of each ash tree.  Look at page 245-5 of this pdf.  You only need to put about an inch depth around the base of the tree and only out about 2 feet.  Leave some space between the actual tree trunk and the mulch.  Here's the pdf:   https://cmg.extension.colostate.edu/Gardennotes/245.pdf  2. Be sure to water your tree, in fact the entire landscape if we have a dry winter.  Trees need about an inch of water every month during the fall and winter.  You'll need to keep track of the snowfall and estimate how much water it would melt down to.  Here's a fact sheet on fall and winter watering.   https://extension.colostate.edu/topic-areas/yard-garden/fall-and-winter-watering-7-211/  3.  No need to add additional water during the summer.  No need to root water or fertilize the tree.  We had a pretty wet May, and the tree probably put on more leaves than it could handle.  Based upon the appearance of your landscape, the tree is getting enough water.    4. No need to send me the EAB treatment.  Here's our fact sheet on EAB treatment.  Take a look at the table at the bottom.  It lists several treatments, one of which Save-a-Tree is probably using.  However, many people prefer to use a pesticide that can be applied every two years rather than every year.  You may want to ask them about that.  https://extension.colostate.edu/topic-areas/insects/insecticides-used-to-control-emerald-ash-borer-on-residential-shade-trees-5-626/  Let me know if you have further questions.  Enjoy your tree!

responder: The Question Asker Replied August 15, 2024, 1:10 AM EDT
response: Jeff, thank you.  Your expertise, and kind and generous efforts are very much appreciated.   - - Henry Reckler The Question Asker Replied August 15, 2024, 1:10 AM EDT

responder: Jeff C, Master Gardener Volunteer Replied August 16, 2024, 12:59 PM EDT
response: You're welcome.