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Tent caterpillars could reach peak numbers this year

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They’ve spent the winter regrouping and multiplying, so when the snow melts, a virtual army of tent caterpillars is ready for an all-out assault on Hubbard County.

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Little brown egg masses have been growing all winter on tree branches and shrubs, getting ready to hatch – and hatch a dastardly plot.

They want to defoliate everything in sight, especially high value oaks, aspen, birch, basswoods, ornamental foliage and perennials.

If you see egg masses, pick them off and burn them, or seal them in tied trash bags to suffocate them, suggest tree experts Christine Jessen, Steph Paulson and Elena Teich.

“This year should be the high peak,” said Teich, a DNR forester. “Cold weather doesn’t kill them.”

Often mistakenly called army worms, the egg masses shouldn’t just be thrown into the garbage or composted where they can breed even more.

Some residents have resorted to fire, a suggestion that makes the women cringe.

“We don’t want people burning trees,” said Paulson, Park Rapids’ city forester.

Warm weather this weekend should make some buds pop. Tent caterpillars love tasty morsels from crabapple trees, Jessen said.

Fruit trees, small fruit crops and gardens are tempting targets.

But with drought conditions settling in last fall, many trees are vulnerable, despite ample snowfall. In a weakened state, some may not be able to fight off the predators.

The DNR states this is a good news-bad news situation.

Defoliating the trees removes their protective cover and can stunt growth.

But the worms provide a ready food source for birds feeding their young. Caterpillar excrement (frass) is a good fertilizer, adding nitrogen to the soil.

But the bugs stink when squished, Jessen said with her nose turned up. And they will leave a stain.

There are sprays that can combat the worms on smaller trees, but an all-out aerial assault is recommended.

“Hand harvesting is the easiest and best,” Jessen said.

Nighttime is best, when they all congregate back at the tent.

Unfortunately, birds aren’t much of a help.

“They’re icky-tasting bugs that birds don’t enjoy,” she said.

So the best method is to get out there now before the egg masses hatch.

There are products you can use on the trunks of shrubs and trees. That prevents caterpillars from climbing up them.

An insecticide will eradicate the young caterpillars. But spraying will only affect this year’s crop of caterpillars.

Moths are “strong fliers” and can move around, laying new eggs over the summer that will survive over the winter.

But Teich shows studies with graphs indicating this year could be the peak year.

And if you decide to spray the back yard, a commercial applicator should be called. The pesticides can harm other plants.

Sarah Smith, Park Rapids Enterprise

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