Jeff Lowenfels: Rolling with birch leaf pests

Marc Lester

At first I thought those hundreds of rolled-up leaves on the two old birches holding the hammock were catkins, those long, thin flowers we see in the spring. Of course, that was easy to think with a view from the hammock. Upon closer examination, it became clear that these were not flowers, but rather rolled up leaves. And, it became clear that all the birch trees on the property had similar leaves.

In fact, I dare say that if you go out and check your own birch trees today, you will also find rolled leaves, thousands of them. This is the work of Epinotia solandrian, one of a couple of animals called "birch leaf rollers." In fact, look down on the ground and you will find plenty of leaves there as well. They often drop off the tree after a while.

Open one of these neatly rolled "cigars" and you won't find a skilled Cuban tobacconist, nor will your find the Epinotia solandrian caterpillar which was actually responsible for the leaf roll. You will find some waste products, but no "worm." In May, these hatched from eggs deposited on the trees last August. (You no doubt saw them on windows and hanging by threads from trees). They ate a bunch of newly forming spring leaves while young (and light-colored), which explains the ragged, skeletal leaves on your trees in addition to the rolled-up ones.

Right about now the caterpillars drop out of their cigars and once on the ground will morph into pupae from which moths will emerge in August. These will then lay reddish-brown eggs on the twigs of trees and the cycle will start over next spring.

So, my prediction is that we are not going to have the greatest looking birch trees this summer. Tops are thin and thread-bare and this seems to be a very heavy infestation of rolled leaves. It happens from time to time when the conditions are right, which they obviously are this year.

So, what to do about this? Well, there really isn't anything you can do at this point. You might have been able to control some of the population of caterpillars with Bt products while they were still eating leaves, but the numbers were really high, so it is doubtful you would have had much impact. By now, they are either morphing into moths or at the very least, stopped eating so these products are useless. The point is: do not fall victim to some scam to spray your trees! The caterpillars are gone. The rolling is finished.

All you can really do now is vigorously rake under your birch trees and try and reduce the numbers of pupae that turn into moths. I suppose you can also mow over your takings and destroy the pupae.

As for your trees, they will make it ... this year. In fact, a healthy birch tree can survive several years of roller infestations, by which time Nature usually supplies the predators that bring the numbers of leaf rollers into balance. (Perhaps this is why there are so many robins hunting around in your yard this year).

Finally, to ensure that your trees are healthy you need to make sure they get enough water, something we have not had to really worry about this year. In addition, you should ensure that the tree is adequately nourished. This is accomplished by mulching up in place the leaves that fall from them. Short of this, you can mulch under the drop line now with leaves. If not, you can fertilize with an organic fertilizer.

Hmm, now I am thinking I might have another use for that dandelion hunting, Shop-Vac: sucking up Epinotia solandrian.

Jeff's Alaska Garden Calendar

Harvest: Lettuces, radishes, early pod peas.

Tomatoes and bees: Be the bee and pollinate your tomato and cucumber flowers with a Q-tip or a small paint brush. You can also "hit" your stems with an electric toothbrush and vibrate the flowers to release pollen.

Clean up: Nothing helps a yard look better than a bit of cleaning up. Put tools away. Collect used pots etc. You know what to do.

Stake: Peonies, delphiniums and other tall plants so they are not damaged by rains.