Warding off caterpillars

Tent caterpillars hatch and feed in early spring.

Aubin van Berckel

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Recently, I spent an hour wandering through the orchard, stroking trees. Although an observer might have assumed I was a raging nut bar, I was actually diligently engaged in mechanical plague control. On a “search and destroy” mission, I was out to get the tent caterpillars at the smallest and most vulnerable stage of their life cycle, their eggs. A bright winter day, with the trees semi-dormant and bare-branched, is the perfect time to look for the egg cases. They remind me slightly of bandages wrapped around the twigs.

They are so well camouflaged, that at first they are invisible. However, once your eyes have learned to recognize them, they become easier and easier to find.

The other day, in the space of the hour, I found seventeen little bands, and the majority were discovered on the last tree I checked. Whether our mirabelle attracted more egg-laying moths last fall than the apple and pear trees, or whether I was simply getting better at “search and destroy”, I cannot say. Over the hour, I made the following observations.

- the egg cases most often look like a blob of fine Styrofoam

- they vary in colour from beige to dark-brown

- they are frequently stained with algae

- they often stick to the ends of the new growth, close to the flower buds (maybe mother moth looks for nutrient-rich sites for offspring)

- they also can be found at branching points, nestled in the wrinkles of the bark (possible deliberate camouflage choice by mother moth)

- they seem to occur more often on the south-facing side of the tree.

To find them I use my hands as well as my eyes. I gently stroke each branch, each twig, pulling them through my un-gloved fingers, feeling for the tell-tale rough bump that is an egg case. Most of them are easy to peel off, but I always do a second scrape to ensure that I have not missed any of the tiny dots. If you look at the side of the case that was pressed against the tree, it is easy to see the individual egg cells. There are hundreds of them in a space the size of a fingernail. Each one, if allowed to, will turn into a voracious tiny wriggling larva that will soon eat its way into something monstrously larger. It is only since I have observed tent caterpillars, that I fully appreciate the huge appetite of Eric Carle’s iconic green worm.

Tent caterpillars generally follow a cyclical pattern of boom and bust, somewhere between seven and eleven years. They hatch and feed in early spring; (preference given to alder trees, beech, birch, hawthorns, and orchard fruits, especially apples) they pupate early summer; (this means that the decimated host trees can have a second leafing and recover from the caterpillar damage) re-emerge with wings (disappointingly nondescript), mate, and lay their eggs in the fall. The egg cases can survive rain, snow, freezing, and repeated thawing. The outer shell is space-age impervious. Even if it looks black and sodden, it is likely that inside the little ova glued to the branch are safe and sound, and growing.

If you feel at all squeamish about scraping them off, remember that once they hatch they become genuinely creepy.

Don’t wait. Do it now. Do it often.

AUBIN VAN BERCKEL

special to the Undercurrent