On a recent site visit, I noticed a Scots Pine that seemed to be bare, and moving!
What was going on? European Pine Sawfly!
European Pine Sawfly can attack Scots Pine and Mugo Pine and strip it of foliage.
In a matter of days, the tree can be bare:
So, the first question is “What is a Sawfly and How does that differ from a caterpillar?”
The following video by Dr. Dave Shetlar general defoliators that differentiate prolegs between a sawfly (6-9 pair of prolegs) and caterpillar (2-5 pair of Prolegs).
https://www.youtube.com/watch?v=-_akBNHkaMg&t=11s
So how does sawfly feed on pines. They eat last year’s foliage and feed in large groups.
A tree can be defoliated in days.
European Pine Sawfly is an invasive species of sawfly and can devastate foliage as shown in this University of Kentucky, You Tube Video:
https://www.youtube.com/watch?v=1eOwLVTDSSc
One sign of infestation is bare foliage.
Another observation is pieces of needles and foliage on the ground below the tree.
After several days, the tree could be stripped bare of last year’s foliage.
The are other Sawfly that can attack pines. The Red Headed Sawfly can be a problem later in the season as Joe Boggs points out in the following article:
https://bygl.osu.edu/index.php/node/1831
In addition to Scots Pine, European Sawfly can attack Mugo Pine:
So, what can be done to solve the problem?
Michigan State University suggests the following:
“Control measures are directed at the young larvae. Remove larvae by pruning out a colony found on a branch using a strong jet of water to blast the larvae off of the plant, or by using an insecticide such as cyfluthrin, permethrin, insecticidal soap and spinosad. When using a pesticide, it is best to spot-treat areas of infestation since they are often localized. Always follow label directions.”
Scouting should be done in May. The full article is attached:
https://www.canr.msu.edu/news/check_pines_now_for_european_pine_sawfly_larvae
Healthy trees will have lush green foliage like this White Pine:
Or this Canadian Hemlock:
So, what else can kill and evergreen?
It could be a heat island or salt damage like this Mugo Pine in this parking lot.
It could be that the plant was mulched too heavily
or planted too deeply.
But don’t despair. The new growth will expand and fill in the tree. But the grown from last year will not grow back.
This is another example of the benefits of scouting in the landscape. A walk around your yard every week can help catch and solve problems early.
Happy coming of Summer!
