Hi Eugene, 

The leaf drop in your tree is possibly due to anthracnose, a fungus that particularly does well in cold, rainy spring weather. This typically shouldn't harm the tree and leaves should continue to leaf out. I would wait and monitor the tree over the next couple of weeks to see if the leaf drop stops, as the hot/dry weather should control the fungal disease on its own. With anthracnose on ash, you'll typically see some brown or tan lesions on the leaves and maybe some curling. If you take a closer look at the leaves that fell, do you see anything like that on the leaves?

Hania

Hi Hania,

There are some brown or tan lesions on some leaves.  For about three weeks this tree dropped up to a bag of leaves per day.  It has been a week since your reply and the leaves are dropping at a slower rate. That said, the tree has far fewer leaves than it started with, so drop as a percentage of what remains is concerning.  The tree may now have only 25% of the leaves it started with (See pictures).  It is difficult to see of new leaves are starting. If many more leaves fall, it will have no leaves at all.

1) Can this tree survive such a large loss of leaves?

2) Should we water more?

3) We feed the lawn beneath the tree with Richlawn lawn food.  Should we use food stakes around the tree?

4) Could these symptoms point to something else like the bore ash beetle?

5) Any other suggestions?

Thanks,

Eugene Smith

<personal data hidden>

Hi Eugene,

1) Here is a helpful resource regarding anthracnose on ash: https://hortnews.extension.iastate.edu/2007/5-23/ash_anthracnose.html. It indicates that anthracnose can lead to the complete loss of leaves with a severe infection of the fungus and it should produce a second flush of leaves afterwards. One severe episode of anthracnose and leaf drop shouldn't harm a healthy tree; rather, repeating infection over several years can harm the tree. 

2) A mature tree generally requires about 10 gallons of water per inch in diameter of the trunk at breast height every two weeks during the growing season. So, if your tree is 12" in diameter at breast height, you'll want to apply about 120 gallons of water every two weeks or so. Since your tree is located in the lawn, it's receiving water via the lawn irrigation system and likely is already receiving enough water. However, if you're able to calculate how many gallons of water you're applying via your irrigation system, you'll know if the tree is getting enough water or if it needs supplemental watering. 

3) Considering this is a mature tree, your lawn fertilization should be adequate for your tree.

5) Rapid defoliation of leaves is not a typical symptom of emerald ash borer. Rather, ash trees affected by emerald ash borer typically decline over a period of 2-4 years. Symptoms to look for would include branch dieback, vertical splits in the bark, increased woodpecker activity, and holes in the trunk. Here is some more information regarding what to look for: https://csfs.colostate.edu/forest-management/eab-what-you-can-do/. Depending on where you live within Jefferson County, it would likely be a good idea to start treating your tree for emerald ash borer if you do value this tree and aren't already treating it for emerald ash borer.

6) If possible, I would clean up and discard the fallen leaves to prevent further spread of the spores.

Hania