chomp chomp

In my experience, fewer insects do more damage than sawflies. More specifically, sawfly larva. I have encountered two types: European Pine Sawfly, and (most recently) Dogwood Sawfly. This post will deal with the European Pine Sawfly.

As the name suggests, European Pine Sawflies are from Europe and eat pine needles. Their favorite types of pines are Mugo pines (Pinus mugo) and Eastern White pine (Pinus strobus). The larva are incredibly aggressive eaters and can defoliate a mature pine in about a week, and small Mugo in a few days. The damage caused by the larva is not lethal to the plant. Once the larva stop eating and drop to the ground to pupate, the pines actually grow new needles and are otherwise healthy. But if the larva are allowed to chow down for years on end, the prolonged stress and abuse will kill the plant.

Below is a shot of a White pine branch completely defoliated. This tree is about twenty feet tall.

Another White pine next to the tree in the photo above. Look closely and you can see that little needle nubs are all that the larva leave behind.

A close-up of European Pine Sawfly larva on a Mugo pine. The larva are about a half inch long, light green on the bottom and gray/blue on the top with a black head.

Do you see how the two larva in the center of the photo are curved backward? That is their defensive posture. I'm not quite sure how that pose will defend them. Perhaps it makes them look bigger and scarier to predators.

Personally, the scary thing that the larva do (which is very characteristic of the species) is to raise the front half of their bodies when you walk by their plant. If you're not expecting it, they make it look like the plant is moving on its own.

(sorry the video isn't the clearest. just watch for the "needles" to move)

Ew. Creeps me out every time.

The larva of European Pine Sawfly start chowing down in mid May. There is actually an easy way to know when to start checking your pines for the larva: After the magnolias finish blooming and before the lilacs start to bloom. Fortunately I have a client with a magnolia, so I can easily know when to check for sawfly larva at my other clients. If you don't have a magnolia nearby, don't worry; there's bound to be a lilac within sight of your home or workplace. When the lilac buds start to swell and have a color but are not open yet, it's time to inspect your pines. But act fast - when the lilacs are in full bloom the larva are about to move to the next stage of their life cycle and they'll be impervious to any insecticides.

How do you get rid of these creepy crawlies? I use Bonide Systemic Insect Control concentrate and have had great success. I follow the bottle instructions and only need one application to kill the larva. If your garden center doesn't carry Bonide products, something with Acephate as the active ingredient will do the job.