Unusual disease outbreak in ash trees

Lots of local news coverage on the impending invasion of the emerald ash borer has many owners of ash trees alert for any unusual symptoms. So I was not surprised by the number of recent calls I’ve been getting about blighted ash leaves. Leaf drop in mid May is a common phenomenon, especially when it’s rainy when the leaves are just expanding. The culprit usually is a leaf disease called ash anthracnose which, while the symptoms can be alarming, it’s generally temporary and pretty harmless. But when I got two different calls yesterday-on Memorial Day- in which both clients used the word “orange’ in describing the symptoms- I realized something unusual was going on. Here’s what I found at a client’s property in Pottstown:

ash

ash rust2

ash rust

The disease is ash rust, Puccinia sparganioides. Spores from the disease on ash cannot infect another ash. They can only infect an alternate host, which is cordgrass which grows in salt marshes. Ash rust is common near salt marshes. But we are quite a distance from the nearest cordgrass marsh, making this a rather unusual event.

Diagnosis: Probably herbicide injury

On Monday I checked on an ash tree for a client in East Greenville.  She said the leaves appeared to be wilting.

The ash tree

The ash tree

Well, they didn’t really look wilted to me, but they were distorted and curled.

The curled ash leaves

The curled ash leaves

The curled ash leavesThe curled ash leaves
I unrolled some of them to check for pests; none were there.  No aphids, no silk from any caterpillars.  There was an outdoor fireplace nearby.  But if that were the cause, I would expect the symptoms to be the worst closest to where the fire would have been.

 

 

 

 

 

Next to the ash is a young saucer magnolia.  Last year I treated it for a bad magnolia scale infestation; so while I was there, I examined it.  The scale was gone, but it too had a lot of distorted leaves.  And, like the ash, no pests, no aphids.

The magnolia

The magnolia

When trees of different species have the same symptoms, it’s probably abiotic – not a disease or a pest.  Pests and diseases are usually host-specific.
Near the ash and magnolia is a Kousa dogwood.  Same thing – distorted leaves.  And the type of distortion that is generally seen with certain herbicide poisoning.  That is, elongated parallel veins and interveinal chlerosis.

Kousa dogwood

Kousa dogwood

Kousa dogwood leaves

Kousa dogwood leaves

There is another ash a few hundred feet away also at the rear of the backyard.  It has the same symptoms, only even more pronounced.

The other ash

The other ash

Well, all the symptoms are consistent with the effect of herbicides, but the client’s lawn is definitely not weed free.  If that is the cause, the likely reason is spray drift from the hay field adjacent to the yard.  The field looks very clean, hardly any weeds.

The hay field

The hay field

So that is my theory – all the trees were damaged by herbicide drift from the application to the hay field.  And that is what I told the client.  And she confirmed that the field was recently sprayed.  She will ask the farmer to be more careful in the future.