Web tents, dark foam = caterpillars

By Eric Barrett

OSU Extension

If your trees have been infested with “web tents” in the forks of branches in past years, be ready for it to happen again.

These tents are formed by caterpillars that hatched around April 15 here in the Mahoning Valley.

The caterpillars are small larvae right now, about one-tenth of an inch long. They are black and already have started to make small, white silken tents.

You’ll need to get up close and personal to see these.

When you spot these larvae, nearby will be what is left of the egg mass. It is usually on a twig the size of a pencil and looks like dark gray to black foam surrounding the twig.

If this egg mass was found before the hatch, removal of the egg mass would have been the easiest way to control this pest.

These caterpillars prefer wild cherry, crab apples and fruit trees. But they are frequently found on oak, maple, hawthorn and other deciduous trees.

What should a gardener do to prevent these caterpillars from defoliating the tree?

Right now there are many options.

First, if the nest can be reached, the simple “grab and stomp” method is highly effective. Yes, just scrape the tent away with your hand and stomp on it with your foot.

The best time to remove tents is after dark when larvae are inside. During the day, the larvae will be sunning themselves and feasting on flower and leaf buds.

Do not use any folklore treatments such as ‘“burning the tent.” This is dangerous and destructive to trees.

Gardeners can use biological controls, such as Bacillus thuringiensis (Bt), to control young caterpillars. It affects only the larvae while they are small.

Other biological controls may take care of the larvae if certain conditions exist.

Full-grown caterpillars will start to become apparent by mid-May.

These caterpillars are nearly 2 inches in length, hairy and black. They have colored stripes and light blue dots on their backs.

They are nearly impossible to control with anything other than the “grab and stomp” method.

Trees that lose all of their leaves in May due to feeding by these caterpillars will re-foliate. But the trees will be under stress as they will take extra energy from the roots to put on new leaves.

For more details. visit http://go.osu.edu/TentCaterpillars.

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