Monday, August 24, 2009

More Tree Pests - Need Help

Having had success in identifying pests through the blog in the past, I am requesting help yet again. My neighbours alerted me to the problem of the willow trees in our area. The leaves are turning brown and show areas of skeletonization and holes eaten through them.
Browning of leaves on willow tree in La Ronge:

There are tiny black insects under many leaves (not even 1 mm long) as well as what looks like tiny black flecks of excrement.
Tiny black insects on willow leaves (click to see closer view):

Today, I spotted a yellow-headed larva (or caterpillar, but I suspect a larva) with a green body crawling along one of the leaves. Between Google and me, I think this may be a sawfly larva.
Larva vs. caterpillar on willow tree:

Also, there are many 5-7 mm web-like silken cocoons on the upper surfaces of the leaves. Many contain what looks like a black grain of rice. I assume something must have matured in these little cocoons and already moved on, since I don't find anything alive and moving inside of them. An Australian website describing their own problem with a willow sawfly shows a picture with a similar-looking cocoon.
Cocoons of willow tree pest:

There are several winged insects flying about the tree, but I'm not sure which is pest or friend. Besides, I'm better at photographing the slow-moving critters.

In a likely-unrelated matter, the tart cherry trees didn't produce any fruit this year. They did have blossoms in spring followed by green fruit, but then the fruit just seemed to disappear off all four trees. I have no idea what happened. There doesn't appear to be any disease plaguing the trees. In previous years, we had pear slugs (which are also sawflies), but those never showed up this year.
Tart cherry "Carmine Jewel" with no fruit:


Karen said...

Can't help with pests, unfortunately.

Is something eating the green fruit on your cherry tree?

Cassandra said...

We have a 'Cupid' sour cherry, which is similar to the Carmine Jewel. Ours is not very old, and bloomed for the first time this year. It made two green cherries, but then they sort of shrivelled up. They're still on the tree, but I don't think even the birds will want them. We moved the tree this spring, which I thought was the problem, but maybe they had the same problem as yours. Bad weather, maybe? Not enough rain?

Gardenista said...

Cassandra - Yes, I really wonder if it was some odd sequence of unusual weather that resulted in the cherry failure. Our produced fruit for the first time last year, so we would have expected a lot more fruit this year. I can't imagine anything eating the green cherries, since there are so many edible wild berries all around us.

Anonymous said...

just surfing the web looking for answers to problems with the willow trees in the area. It's exactly the same as what you show here; the brown blotches with silky-bubble cocoons on the leaves.
Just wondered if you ever found out what it was and how to treat it, or whether the trees recovered naturally.

Gardenista said...

Update- whatever that was, it did not kill the trees and
Seems to be okay this year. Perhaps it was a good year for that pest last year or if just goes in cycles? Not sure.

Karl said...

I have plums in the front yard and noticed that when the fruit was really tiny and green, much as you describe with your cherries, the purple grackles came in and ate them. You may need to net them as soon as the flowers begin to fruit.