sudden leaf drop on green ash

RogerM

Well-Known Member
Leaves suddenly dropping on 25 yr old green ash, Appear "normal" when dropping. No visible fungus or
wilt. ANy guesses? Anthracnose, leaf spot, suddeness leaf droppedness?
 

mrtree

Well-Known Member
Check to see if the youngest leaflets on the tree are purple and curled. Inside you will find very small mites. Saw a tree like this yesterday that was shedding leaves as the rolled leaves opened.
 

TProsser

New Member
Location
Minnetrista MN
Its a leaf fungus disease called ash anthracnose. Very common here on ash trees starting about 10 years ago. We get it every spring. Makes the phone ring off the hook for about a week.

Nothing we have tried has worked in getting predictable protection
 

mrtree

Well-Known Member
I may not be ash anthracnose, if it is a fungus I would imagine it is more likely to be ash leaf spot in my experience. OF course the incidence of each fungus is likely variable across North America.

What RogerM has mentioned though is that the leaves appear normal when falling. That indicates to me it is not a fungus.
 

KyLimbwalker

Well-Known Member
Location
Louisville, KY
This symptom has been attributed to Ash anthracnose, though no one really knows what causes the leaf drop (as the leaves look perfectly healthy). Here's what I've drummed up:

1) ash anthracnose is a foliar fungus that perennially infects the same trees. Normally looks like someone took a lighter to the ends of some of the leaflets.
2) leaf drop is associated with this fungus in some but not all years
3) the infection is normally not serious, unless leaf drop occurs in 3 out of five years.
4) Cultural controls (such as raking and removing the annual leaves, and thinning out the canopy) are recommended.

5) Chemical controls include a basal drench fungicide or spray (Cleary's 3336, I think)
 

TC

Well-Known Member
Ky, any idea what the optimum weather conditions are for this fungi to thrive?

Warm and damp?

How would thinning out the canopy help? better air circulation?
 

Mahk_Adams

Active Member
[ QUOTE ]
...Ash anthracnose...

[/ QUOTE ]


I've had some experience with this.


[ QUOTE ]
1) ash anthracnose is a foliar fungus that perennially infects the same trees. Normally looks like someone took a lighter to the ends of some of the leaflets.


[/ QUOTE ]

Yes, although the leaflets don't look blackened, but only 'withered', 'heated', or 'dried'.

[ QUOTE ]
2) leaf drop is associated with this fungus in some but not all years


[/ QUOTE ]

Because of...weather, sanitation, vitality (of the tree and or fungus)??


[ QUOTE ]
3) the infection is normally not serious, unless leaf drop occurs in 3 out of five years.


[/ QUOTE ]

Haven't heard those numbers before, but, because the tree has to refoliate, it seems a reasonable guessestimate.

[ QUOTE ]
4) Cultural controls (such as raking and removing the annual leaves, and thinning out the canopy) are recommended.

[/ QUOTE ]


I would recommend sanitation (raking and removing the leaves), but I would certainly NOT recommend thinning out the canopy. What is the rationale or that?


[ QUOTE ]
5) Chemical controls include a basal drench fungicide or spray (Cleary's 3336, I think)

[/ QUOTE ]

I have only used sanitation, which worked well.
 

KyLimbwalker

Well-Known Member
Location
Louisville, KY
[ QUOTE ]

I would recommend sanitation (raking and removing the leaves), but I would certainly NOT recommend thinning out the canopy. What is the rationale or that?


[ QUOTE ]
5) Chemical controls include a basal drench fungicide or spray (Cleary's 3336, I think)

[/ QUOTE ]

I have only used sanitation, which worked well.

[/ QUOTE ]


Since all anthracnoses are foliar fungi, they thrive on moist conditions and less direct sunlight. I think the rationale for the thinning include:

1) more air movement through the canopy (creating less moist conditions)

2) less future inoculants (in the leaves)

Also- we see anthracnose on almost every ash in the city, to some degree or another. The only tree that I have seen drop leaves are those that have been topped or over-pruned in the past (i.e. very thick canopies). Also, the leaf drops have occurred before the tips "tip" you off to an infection.

Ash seems to live with this disease pretty well. Sanitation should be a yearly practise- but should not be considered a replacement for fungicides in a severely affected tree.
 

ATH

Well-Known Member
Location
Ohio
Resurrecting an old thread.

I've seen perfectly green leaves dropping on a few trees. First noticed on a tree we treated with Tree-Age (R10) last week. Another client that we treated with soil-applied imidacloprid emailed because one of his was doing it again (did 2 years ago a little later in the summer. Then I got a call from another arborist in town asking about the same thing. He also found some about 50 miles away that looked the same.

I'm wondering anthracnose without the spots???

Arborjet rep suggested petiole borer. I thought they looked like they had a fully intact petiole, but I will run back down the road tomorrow to look again...

I think the wilted-looking leaves were yesterday's crop, not coming off the tree that way.

There are not enough down to impact the overall health of the tree.

20200603_081525.jpg 20200603_081529.jpg 20200603_081532.jpg
 

KTSmith

Well-Known Member
I used to think that leaf shedding due to anthracnose would not occur prior to obvious necrosis and the typical foliar symptom progression.
In recent years, I've come around to accept the concept of pre-symptomatic leaf shedding in ash. Does it really occur that way? I don't know. Would be a good MS project.
 
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Nish

Well-Known Member
Location
North Carolina
Sounds like the same puzzle I've got with a white ash in Durham, NC. Sudden and premature leaf and petiole abscission with no signs of damage from insects, anthracnose, etc. Alarming because it started happening shortly after our emamectin benzoate injection. Lots of rain (too much rain), but flooding doesn't seem likely. The leaves in the photo below have been on the ground awhile. Client had been raking them away. These were the last batch that came of the tree but the shedding apparently started tapering off.

Screen Shot 2020-06-06 at 5.07.20 AM.png
 
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ATH

Well-Known Member
Location
Ohio
Sounds like the same puzzle I've got with a white ash in Durham, NC. Sudden and premature leaf and petiole abscission with no signs of damage from insects, anthracnose, etc. Alarming because it started happening shortly after our emamectin benzoate injection. Lots of rain (too much rain), but flooding doesn't seem likely. The leaves in the photo below have been on the ground awhile. Client had been raking them away. These were the last batch that came of the tree but the shedding apparently started tapering off.
I talked to ArborJet rep as the first tree we noticed was one we injected a week prior. But I had also gotten a call from a client where we just did soil applied imidacloprid. Another arborist in the area found some leaf drop from untreated trees as well as treated.

ArborJet clarified that we used their product. Said the other major one the the market is more likely to have some minor phytotoxicity...

Without my prompting, he also suggested anthracnose after talking to their pathologist. So I think that is what I am going with for working hypothesis. Will try to get back over on a week day to send off some samples.

Pics from today. Only a few fresh leaves on the ground:
20200606_190611.jpg
20200606_190703.jpg
20200606_190802.jpg
20200606_190820.jpg
 

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