The Munch of the Songy Moth

While you were perusing the last couple of day’s information there might have been a caveat forming in your mind. 

Lepidoptera - lovely! 
Songy Moth - bane of your summer existence!

And guess what, the Spongy Moth, like other Lepidoptera, also loves oaks - red and white oak in particular, poplar, and white birch. 

So what can you do about this? Especially seeing as the typical way of combating them involves spraying an insecticide purpose-built (it must be ingested by chewing insects) to kill Lepidoptera caterpillars indiscriminately?

Why do people choose insecticides in the first place?

There are a few possible reasons. It may be the only thing that they know about. For many though, it’s the easy option. They don’t want to have to put the amount of work necessary into hand scraping and squishing all of the caterpillars and eggs on their property . Especially if you live near the beach, you really come there to enjoy it, not hand scrape Lepidoptera larvae.

Interestingly, the Songy moth isn’t really new. It’s been in North America for 130 years or so. How did they get here?

Apparently a man wanted a better silkworm to start a silk industry in North America. I’m noticing a pattern with many of these explosions of destructive proportions, no? 

Now, in the last 20 years or so, the Songy Moth was accidentally introduced on shipments of ornamental trees from Japan and Europe. 

These caterpillars can munch about a meter a day in leaves, raining frass (bug poop) down on anything found below them. That can really ruin a picnic with the grandkids. Then again, so can killing all Lepidoptera caterpillars period just because we dislike Spongy moths. What to do? What to do?

Have you heard of komomaki?

Developed in Japan during the Edo period to protect pine trees against another kind of moth, these straw bands can be replicated here with burlap strips tied around tree trunks. It’s actually part of the recommendation from Ontario’s Invading Species Awareness Program. 

They can become a bit of a catch-all. However, because you would be applying them only to trees you know have European Songy moth caterpillars, and you wouldn’t be leaving them on till Spring for any bug to overwinter in, I think they are a less indiscriminate option than Btk. You can burn them in the traditional fashion after you take them off the tree and use the ashes to enrich your garden, like they did in Japan. Or you can place it in a bucket of hot soapy water for a couple days and then into the garbage. 

Back to the caterpillar frass

I was reading something really interesting on frass and how it actually can cause a physiological reaction in the plants nearby. We all know that plants have defense systems that they can muster to suppress animal and bug attacks or to combat disease. It’s much like our own immune system or how we know the taste of certain things means we shouldn’t put them in our mouth (why it’s hard to get kids to eat bitter things). 

So my question is, do the chitins (kite~ins), or tiny pieces of exoskeleton that are in the frass from the Songy Moths, signal the trees to fight or suppress their fight response?

Because it can happen either way (study about armyworms and maize).

If the frass from the Songy Moth caterpillars that is accumulating under the trees is signaling the trees to mount a defense, then this is a good thing and all we need to do is support the trees in the best way we can and allow them to fight for themselves. Make sure they get enough water and nutrients, don’t cause additional stress by pruning and check those burlap strips every week or so to remove as many caterpillars as possible. 

But what if this is an armyworm/maize sort of response instead of an acacia/giraffe sort of response?

Unfortunately I don’t know.

If it is an armyworm/maize scenario then any interaction of these caterpillars with the tree is further weakening the tree. Their saliva, their frass, any chemical byproduct, may be destroying the tree's natural responses so that it can’t actually fend for itself. That is not good for the trees concerned. 

Apparently the Moths run a three year cycle and eventually collapse on their own, recurring every decade or so. Knowing this will help you understand your particular ecospheres' interaction with these moths. Has it been a bad year or two of raining frass? It's almost done. Squish away knowing that you’ll soon have your reprieve. 

I’ll let you know if I find out any more on the frass front.