IT'S ALIVE!

Courtesy of Jesse H, a resident
of the First Ward

 “The forest tent caterpillar is an important leaf-eating (defoliating) caterpillar in Wisconsin. Some people call forest tent caterpillars 'army worms' because as they travel across the ground they look like marching soldiers.” - DNR website

If you've been out and about, especially in the First Ward, you may have noticed what looks like large spiderwebs up in the trees. Frankly, they look rather creepy, like some biblical plague come to roost.

In caterpillar phase

I asked City Inspector Joe Atwood to look into it and he promptly reached out to the DNR and spoke to an agent. What he was told and reported back to me is that these silk nests we're seeing are tent caterpillars (often referred to as 'army worms') that in time will turn into moths. Contrary to what you would think the DNR considers them a native species whose population spikes from time to time.

Obviously, I'm out of my depth with the regards to their biology, but per the cited article All about forest tent caterpillars there are four stages to their life cycle:

• 
  Egg masses: Forest tent caterpillar eggs are laid in big ball of sticky around twigs and shrubs. Each egg mass may have up to several hundred eggs inside. Laid in late June to mid-July, they will remain in their sticky mass until warming temperatures cause them to hatch in the spring.

• Larvae (i.e., caterpillars): They emerge come late-April to mid-May. They have voracious appetites and can defoliate a tree if there are enough of them. Should they “run out” this is where they get their name: they begin to move in mass in search of more foliage.

• Pupae: Full grown caterpillars will spin silken cocoons in any protected place

• Adult: About 10-14 days after they pupate, the adult moths emerge. Per the DNR, in northern Wisconsin it is most common to see these forest tent caterpillars from late June to mid-July.

They have one week to live during which time they seek to mate and lay eggs before they die. So all those masses in the trees right now is merely Phase 1. When they emerge from their sticky nests in the spring they will be in search of broad-leafed trees and shrubs. All the defoliation they do is caused strictly by the caterpillars. The adult moths got more important things to do in their one week of life.

According to the DNR agent Joe spoke with that if you are concerned about them you can snip off the branch and soak it in soapy water. Contrary to what I suggested to a few folks last week, it is not recommended to burn them given how dry it is right now.

He suggested that you can also purchase BT (bacillus thuringiensis)
spray or oil from a hardware store or local nursery. This spray is organically safe for humans, pets, honeybees and earthworms. Best to treat them, though,before the eggs hatch or before the caterpillars leave the nest. 

What if you just leave them? Well, you're certainly not in violation of any local ordinance. But they're appetite is hearty (although they don't like red maples or conifers) and if you're like us who fight Japanese beetles all summer long, these things can pick you clean just as well.

Good luck and, to quote a well-known movie line from about 15 years ago, "May the odds be ever in your favor!"