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.

Emerald ash borer update

Have you noticed all those purple sticky traps?

Emerald ash borer sticky trap

Emerald ash borer sticky trap

The PA Department of Agriculture has hung them in ash trees all over eastern PA this summer.  My guess is we’re going to find out about a considerable range increase for this terribly destructive insect.  Already this year, 2 new counties have been added to the list, Huntingdon and Wyoming.  IT IS NOW IN THE EASTERN PART OF PA, having been detected just north of Wilkes-Barre.

Things you need to know: – Adults can fly on their own approx. 1/2 mile.  So the pest isn’t moving very fast on its own.

– It gets help in colonizing territory from people moving infested firewood.

– If emerald ash borer gets close to your area, your landscape trees can be treated by soil injections.  Bigger trees can only, so far, be successfully treated by trunk injection of insecticides.  Treatments need to be done annually to be effective.

– Experts do not suggest treating trees unless an infestation has been detected within 15 miles.  To treat before the threat is there is a waste of money.  And trunk injection is an invasive procedure.  Don’t injure the tree with it until you need to.  And don’t believe anyone who tells you that their trunk injection method causes no injury to the tree.

– If your trees are monitored by a competent arborist, you are not likely to be caught by surprise by emerald ash borer.  If it    shows up, you will have time to control it if you choose to.

NEW information: A new chemical is available that is highly effective and lasts more than one season.  Hopefully it will be  legally registered for emerald ash borer control in Pennsylvania soon.  And hopefully the price will come down (it’s very expensive).

MORE NEW information: A new monitoring tool may soon become available.  Recent research on developing a sex attractant (pheromone) has been promising.  The purple monitoring traps now use two aromatic tree oils as attractant.

Still more new information: Research has also uncovered promising indications of natural biological control of emerald ash borer.
We in southeast PA are lucky to have the benefit of a decade of other’s experience and research before having to face the emerald ash borer.