Withered branches on pine bushes

Asked May 18, 2020, 6:30 PM EDT

We have withered needles on our pine needle bushes..
But they look like tiny black flies feeding in them.
Not seen in these pictures as we've had heavy rain the last 12 hours or so.

We don't know what they are or how to treat the bushes?

Cuyahoga County Ohio

3 Responses

Thanks for your question.

Without seeing you insect, I am going to guess that you have European Pine Sawfly. When small, the caterpillar-looking larvae will cause the needles to curl a they feed and turn to a straw color as they are not large enough to eat the whole needle.
As they mature, they will eat all of the needles from last year's growth. I do see some needles that are just the bases of them left. They will leave this year's emerging needles alone and the result is a poodle- looking plant. Control is easy as they only have one generation per year. If you find them, you may pick them off by hand smashing them as you do (I would wear a glove), you may knock them into a container of soapy water, or you may use an insecticide.
The adult sawfly does look like a small black fly.
Here is some further information about the insect and chemicals to control:

https://entomology.ca.uky.edu/ef410

https://ento.psu.edu/extension/factsheets/european-pine-sawfly

https://www.canr.msu.edu/news/check_pines_now_for_european_pine_sawfly_larvae

There are a couple of other things that I think I see in the branch tips. It appears that you have White Pine Weevil as well. This insect does not only attack White Pines, but all pines, spruce, and Douglasfir.
The shoots that are brown and have a hollow tip are an indicator for this insect. I thought I saw that on the middle photo you included.
While too late to do anything about this now, you can treat next year to prevent damage.
Here is a fact sheet about this insect pest:

https://www.canr.msu.edu/news/timing_is_critical_for_white_pine_weevil_control

Treatment time would be about the time the Forsythia are blooming.

The final thing that might be happening, and since it is a photo I am working from and not the plant, is possibly the start of Diplodia Tip Blight. I noticed some dead tips and I am not sure if the weevil has caused it or the disease. Here is information for that that you might review:

https://ohioline.osu.edu/factsheet/plpath-tree-03

If the damage is limited to the areas in the photos you included, then it is probably insect related.
Hope this helps. Thanks for your question.

Thank You Dave M.

We had SO many of sawfly's, that we opted to use some insecticide.. they were completely gone with a day.. they almost look 100% better already..
We'll also keep a closer eye on them for next year.

Thanks again,
Joe & Sheryl

Joe and Sheryl,
So glad I could help out. The sawfly can certainly make a bush look very weird without intervention. Thanks for the question.
Dave