Slug and Cabbage Worm Control on the Cheap

June in Redmond means the slugs have fully woken up and the white butterflies are doing lazy loops over your brassicas like they own the place. They kind of do. The wet maritime climate here is genuinely paradise for both slugs and cabbage worms, which is wonderful news if you are a slug or a cabbage worm and terrible news if you grew kale from seed and were hoping to actually eat it.

Let’s talk about what actually works, what’s cheap, and what the internet has been lying to you about.

Slug Control That Actually Works

Beer Traps

Slugs are attracted to the yeast in beer, not the alcohol. Useful to know, because it means the cheapest, flattest, most expired beer you can find works just as well as a fresh one. Science drop: the CO2 off-gassing from active yeast mimics decaying plant matter, which is basically slug Disneyland. I bury a tuna can lid-deep in the soil near my beds, pour in a couple inches of whatever’s cheapest at Grocery Outlet, and check it in the morning. Results are deeply unpleasant and extremely satisfying.

Copper Tape on Raised Bed Edges

Copper tape gives slugs a mild galvanic shock when they cross it. Their mucus reacts with the copper and they do not enjoy it. Wrap it around the top edge of your raised beds and you’ve got a decent barrier. One roll goes a long way and it’s not expensive at most hardware stores. Two things I learned the hard way, though. Make sure no plants are hanging over the edge and creating a bridge. And actually kill the slugs already inside the bed before you tape it off. Otherwise you’ve just built them a house.

Hand-Picking at Dusk

Free. Works. Requires a headlamp and a willingness to touch something slimy. My daughters refuse to participate, which I respect. Go out about 30 minutes after dark, check the undersides of leaves, the soil line, anywhere damp. Drop them in a container of soapy water. It works better than most people expect, and it costs nothing.

Iron Phosphate Pellets

This is the one I reach for when things get serious. Iron phosphate pellets are safe around kids and pets, which matters because we have both. Slugs eat the bait, stop feeding, and die underground a few days later. The iron phosphate breaks down into nutrients your soil actually uses. Which, now that I think about it, is a pretty elegant ending for something that was eating your spinach.

What Does NOT Work (Sorry, Internet)

Diatomaceous earth sounds great until it rains. In Redmond in June it rains approximately always, so the DE gets wet, clumps, and does nothing. Eggshells are the same story. Slugs will cross both when they’re determined. I tried the eggshell ring approach for an entire season before finally admitting it was theater. Coffee grounds work a little, briefly, until they don’t. Save your grounds for the compost.

Cabbage Worm Control

Floating Row Cover

The white butterflies fluttering around your garden are Pieris rapae, and they are specifically shopping your brassicas for somewhere to lay eggs. Those eggs hatch into pale green caterpillars that will eat your cabbage into a skeleton in about a week. The cheap fix is floating row cover draped over the plants and pinned at the edges. No butterfly lands, no eggs, no worms. Not glamorous. But it’s the most effective thing on this entire list, and a roll lasts for years.

Bt Spray

Bacillus thuringiensis, or Bt, is a naturally occurring soil bacterium that produces proteins toxic to caterpillars specifically. When the worm eats it, the proteins punch holes in their gut lining and they stop feeding within hours. Alright, that’s the last biology tangent, I promise. It’s safe for people, pets, and beneficial insects when used as directed, and it’s cheap at most garden centers. Reapply after rain, which, again, June in Redmond.

Hand-Picking

Same story as the slugs. The worms are green and camouflaged, so look for the frass first (tiny dark pellets on the leaves) and work backwards from there. My youngest actually likes this one. She calls them “squishy worms” and has no mercy, which is honestly the right attitude.

A Small Dog Who Barks at Butterflies

We don’t have one, but a neighbor does. I’m not saying it helps with pest control. I’m not saying it doesn’t either.

The Short Version

Beer traps and iron phosphate for slugs. Row cover and Bt for cabbage worms. Ditch the eggshells. Go outside after dark once in a while. Your kale will lettuce you keep it, if you stay on top of this stuff in June before it spirals.

(I couldn’t help it. Sorry.)

Photo by Miriam Rodergas on Unsplash