Deeply Rooted

Tent worms, army worms and canker worms. We often hear and use these names interchangeable for a very similar issue. There is a web full of caterpillars forming on your tree.

I have had some difficulty researching exactly what the difference is between these caterpillars. As best I can tell, canker worms are black with small white spots. Army worms are also dark but have more military-based colours in their patterns. I still cannot find any consistent information about tent worms.

In the end they will all still make the same silky webs on the fresh growth of young trees. They are most commonly seen in fruiting trees like apples or plums but can sometimes also be found in other varieties. This year I spotted one in a poplar and in a green ash. Cotoneaster shrubs sometimes attract them as well.

For some reason, trees with darker purple foliage tend to attract the worms the most. Shubert Chokecherries and Rosybloom Flowering Crabapples are the most prone.

There are a few methods for removing the worms from your trees:

In the very early stages when they first arrive, you can try removing the webbing in the nest before the worms can spread out. You can wrap and collect the webbing on a stick and catch the majority of the worms in their own web.

One of the simplest methods used is to wait until the heat of the day when the worms retreat from the canopy of the tree onto the trunk. They do this to find shade and avoid the intense heat. Once they have all gathered on the trunk, they are easy to either crush or remove as they’re all isolate in one area.

There are sprays you can use to treat them as well. The problem with the sprays is that you need to spray them directly onto the caterpillars for it to work, making it just as effective as removing them by hand.

If you leave them untreated, they will strip a large portion of the leaves from the tree. I once saw a mature flowering crabapple completely leafless in midsummer once because these caterpillars were never addressed. The tree did recover and thrive the next year, but it took time and care. It is always best to dispose of the canker worms as soon as possible.