Emerald Ash Borer Update June 15, 2015

RIGHT NOW is the time of year that emerald ash borer (EAB) adults are active. Here are some photos I took last Wednesday in Willow Grove, Bucks County, PA.

EAB 5725

This ash tree had some live branches on it a few weeks ago. Landscape maintenance people have cut and removed them.

Wonder where they disposed of them.

EAB 5727

Tree in same parking lot – adults are now emerging and feeding on leaves

EAB 5735

Adults feeding

EAB 5740

They’re inconspicuous; you might not notice them if you are not looking for them.

Not easy to recognize as a beetle when they’re flying. Not easy to see them when they are feeding on the upper leaf surface, but you can spot their shadows if it’s sunny.

EAB 5743

Adult beetles

EAB 5754

EAB 5763

The emerald ash borer is well established now in this portion of Bucks County. I predict that the spread to surrounding areas is now imminent, as many trees are dying, and inevitably the wood of some of them will be unwittingly relocated.

The emerald ash borer is not the only reason for the decline of the health of ash trees in Southeast Pennsylvania. In some of the neighborhoods where we work, the majority of ashes seem to be dying but there is no sign of EAB.

One factor responsible for this is freeze damage from the warm winter and spring three years ago. Yes, you read that right. Freeze damage. Ash trees normally are one of the last species to get leaves in spring – usually the middle of May. But the consistent warm weather tricked them in to breaking bud over two weeks ahead of schedule. Then we had a surprise late cold snap. Ashes in particular were injured, and many have not recovered from the stress, predisposing them to secondary pests.

Speaking of secondary pests, here are photos of some of the ones I see most commonly. These insect are all native, and are not normally considered a serious threat to ash trees as they don’t usually kill healthy trees.

EAB 7466

galleries of Eastern ash bark beetle in green ash

EAB 7465

EAB 7914Eastern ash bark beetle

EAB 4432banded ash borer emerging

EAB 4452banded ash borer – Neoclytus caprea

EAB 6200collected specimens of EAB, banded ash borer,  Tylonotus bimaculatus (Ash and Privet Borer), another native ash borer.

More on ash and privet borer at July 21, 2009

You can see good photos of more ash pests at Michigan Extension Bulletin E-2939 http://www.emeraldashborer.info/files/e-2939.pdf

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Scarlet oak sawfly

These pin oaks are shedding leaves, and large parts of some of them have leaves that look white from the ground.  The culprit is scarlet oak sawfly larvae.

I have never seen damage quite like this from this insect.  It’s unusual for it to reach such a high population that it defoliates the tree like this, and there ARE natural predators that usually keep it in check.  But in this case it could impact the tree’s health, so control would be justified.  Control, by whatever method, would need to be done soon.  Otherwise the larvae will pupate, and later in the year the adult wasps will emerge and lay eggs and there will be another generation!

Imported Willow Leaf Beetle June 12 2012

This weeping willow in Harleysville has adult imported willow leaf beetles feeding on its leaves. They won’t cause much damage. But the population of beetles is rather high, and they will soon lay eggs. When the larvae of the next generation emerge from the eggs, they will feed on the leaves in a skeletonizing pattern, and there will be enough of them to defoliate the tree. The client is aware, and he will probably spray them.

Emerald Ash Borer Scouting

The way this client found me is a little bit strange.  He found my website by googling “bacterial leaf scorch” (I have articles posted about my experiences with BLS).  That’s what another “arborist” told him was wrong with his ash tree.  And that the disease would kill the tree, so he should remove it.  Well, ash trees have a few problems around here of late, but bacterial leaf scorch isn’t one of them.  Anyway, the tree didn’t look good and we talked about the true ash ailments – ash anthracnose (which the tree did have) and emerald ash borer (which hasn’t been found close to here yet).  In the end, he agreed we should inspect the tree for EAB, just to be sure.

Today, Ricky and Dave climbed the tree, and the one next to it, and checked it thoroughly.  Good news – negative for EAB.

The ailing ash

The ailing ash

Holes in leaves

Holes in leaves: from the ground you can’t see them in detail, can’t tell if it’s insect feeding damage; close up it doesn’t look like it. More likely caused by damage to buds from our late frost

We look for any clue - here you can see the wood pile contains ash firewood

We look for any clue – here you can see the wood pile contains ash firewood

hackberry emporer butterfly

While we were getting started, this hackberry emperor butterfly came by and took a liking to the minerals on Dave’s hardhat strap.  (Click the image to see a nice big version!)

Dave and Ricky

Dave and Ricky each went up a tree

a good, closeup inspection of the crown

…and did a good, closeup inspection of the crown.

If you have ash trees and are concerned about emerald ash borer now that it has been discovered in Bucks County, right now is the best time to have them checked.  This is the peak time for emergence of the adult insect.

European Hornets (Followup)

Renee wanted me to help her get rid of the hornets. So I had to decide how to go about it. The most effective way to control European hornets would be to destroy their nest and colony. But we have no idea where the nest is – probably not even on her property. If we went to spray the hornets we see on the trees with an ordinary contact insecticide we’d just kill those individuals present at the time.

So I opted to coat the bark of the trees with a material called dinotefuran. It’s a neonicotinoid, like Merit, with which you may be familiar. But it’s much more soluble, so when applied to the bark of a tree it can be absorbed, and then conducted through the tree’s phloem. And the phloem of the birch branches is where these hornets are feeding.

I made a visit to Renee’s today to check the results. There were no longer any hornets on the tree. But there were MANY on the ground, all either dead or dying.

European hornets

European hornet

So I think we made a good choice. Though we did have to intervene with a pesticide, the one we used – dinotefuran – is unlikely to cause harm other than to the target pest. It is extremely low in toxicity to humans. And with the trunk application method, the material all goes where we want it – in the tree. The only exposure is to whatever eats the tree. And, being so highly soluble, it dies not last very long (like Merit does). So it won’t be affecting beneficial insects like bees next year, after its job is done.

Post Script: I found a really good article since I had this experience. It’s by Frank Santamair, in the Journal of Arboriculture from 1984.

European hornets

European hornetsThese are European hornets.
European hornets
I never really thought of them as tree pests before. When I see them on trees, usually they’re feeding on sugar that’s been excreted by aphids or scale insects, or on the alcoholic wetwood flux  oozing from a mulberry or a dying elm. But I may be changing my mind a little bit , after what I saw today. Renee, from Audubon, showed me these insects, which she had attempted to identify by searching on the internet. She had noticed them before, but could no longer tolerate them because her son was stung by one of them, and it was a pretty bad experience.
They were congregating on two of her river birches. I waved my hand a few inches from a group of them and they didn’t react at all. They really aren’t very aggressive, normally.The branch of the birch tree was stained with sooty mold, indicating sugar, such as from an insect injury.
European hornets
On closer inspection, I could see that the hornets were not feeding on the sugar; they were actually causing the injury that produced it. These hornets had chewed away the bark all the way around one branch, killing it!

I know they need cellulose to make the paper to construct their nests, but this is the first time I’ve seen this type of damage. You learn something new everyday!  One more interesting observation: while I was trying to get a photograph, I watched a baldfaced hornet approach a group of the European hornets.  The Europeans reacted immediately and chased it away. After that, their behavior was completely changed- they were very aggressive toward ME and would no longer let me get close!
(check back later to see what we did about it)