Pikes/Pines | Gypsy moths are on the Hill

A gypsy moth caterpillar (Image: Wikipedia)

A gypsy moth caterpillar (Image: Wikipedia)



In 1852, a gentleman named Etienne Leopold Trouvelot settled in Medford, Massachusetts. He was a portrait artist by trade, but had a strong interest in entomology. In particular he was interested in identifying native silk worms for silk production, which encouraged him to delve into rearing moths. In the 1860s after a visit to France, Trouvelot accidentally let some European gypsy moth caterpillars escape. This escape was relayed to authorities, but it appears nothing was done and the matter was largely forgotten for the time being. After this, Trouvelot drifted from entomology to astronomy, gaining accolades for his celestial illustrations done while teaching Astronomy at Harvard, even having a crater on the moon named after him. In 1882 he returned to France, right about the time people started noticing a bunch of caterpillars in Medford.

And now, 134 years later, we’re preparing to fight the nasty critters here on Capitol Hill.

Troubelot’s little blunder has had lasting, devastating effects. Gypsy moths caterpillars are incredibly voracious and not terribly picking, having been documented eating over 300 species of trees and shrubs. Being non-native they lack some of the normal controls they’d have in their native range in Europe and Northern Africa, so they’ve had few problems spreading across the great hardwood forests of the Northeast, nor defoliating entire orchards (according to the US Forest Service between 1970 and 2010 they defoliated a cumulative 80.4 million acres of plants). To make things worse, the caterpillars use their silk to catch the wind and sail to greener pastures.

By the 1934 the moths spread out of Massachusetts, rampaging across the Northeast. By 1994 they’d made it to Michigan. Today we see them occasionally out West in small numbers, along with their scarier cousins the Asian gypsy moth. Scarier because they’re even less picky and female Asian gypsy moths can actively fly long distances (female Europeans do not), meaning they can spread more rapidly.

Both types are happy stowaways as eggs or larvae. When someone moves, with all their things, to the Hill from New Jersey. When a cheapo (like me) decides to take firewood with him on a cross country car-camping trip instead of paying for those roadside $5 bundles. Or maybe just in a shipping container that didn’t get as closely examined as it should have. Regardless of how they arrives, we don’t want them here.

Now, again, European gypsy moths have been found on Capitol Hill. The Washington State Department of Agriculture (WSDA) sets out thousands of traps across the state every year, looking for presence of these pests. In the past year, they trapped 20 adult moths in the blocks neighboring Group Health.

They plan to get rid of them with an organic pesticide called BtK, which is short for Bacillus thuringiensis kurstaki. This is naturally occurring bacteria is applied by aerial spraying of the inactive, spore form, of BtK specially formulated to kill butterfly and moth caterpillars. These spores don’t activate until they’re ingested by caterpillars, which halts their feeding, before melting them from the inside out. Sounds simple and effective, right?

Some people don’t feel that way and previous spraying has been met with protests, lawsuits, and general outcries. Believe me, I get it — the idea of the government spraying 130 acres around Capitol Hill with a bacteria, benign or otherwise sounds a little creepy. Then there’s the worry that native Lepidopterans (butterflies and moths) will be killed in the process. And of course overuse of BtK can produce resistance to it as a biological control (but that’s a larger discussion I’ll not venture into for the moment).

These concerns are valid, but I still would rather not have gypsy moths. I have seen no concrete science (governmental and not) that suggests that BtK is harmful to people, pets, or any other wild creature besides caterpillars. You’ve ingested it before, sprayed on your nice beautiful organic cabbage, so that cabbage white butterfly caterpillars don’t eat them holey. I’m not saying roll in the stuff, but that it’s not gonna kill us.

As for the Hill’s native Lepidopterans, imagine this: nothing for them to eat, because every square inch has been ravaged by gypsy moths. It’s essentially a case of lesser evils. Kill a few native caterpillars (which can potentially reestablish from elsewhere), to rid ourselves of a scourge. Several studies suggest that the greater impact on native Lepidopterans is from being out-competed by gypsy moths, not from the use of BtK. And of course, it’s not as if all moth and butterfly caterpillars are out and about at the exact same time, also reducing potential impact.

No one really wants a defoliated Hill writhing in gypsy moth caterpillars with nowhere for birds to nest, nothing for many native insects to eat, and of course no summer shade for humans. The WSDA is being very open about this whole process (including corresponding with me frequently over the past week) and plans to hold an open-house to discuss the proposed spraying and gypsy moths (visit here to keep abreast of current information). Some non-native species aren’t as big of a deal and fit into our urban landscape in an acceptable fashion. The gypsy moth is not one of those examples. Thanks a lot Trouvelot.

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6 thoughts on “Pikes/Pines | Gypsy moths are on the Hill

  1. 22 of these nasty critters found within a block or two on Capitol Hill… I’m curious why they’re so concentrated. Has this been investigated?

    • Great question! The type of moth that was found in Capitol Hill is the European gypsy moth. WSDA has detected the moth in the area for the past 4 years: 1 moth in 2012, 1 moth in 2013, 6 moths in 2014, and 22 moths and several egg masses in 2015. The European female gypsy moth does not fly, which is likely why the population remains concentrated – they aren’t generally able to spread rapidly owing to their lack of flight.