My collard green plants were hit by cross striped cabbage worms this week. I gathered some to observe, leaving them some greens to eat. In the morning there was about a tablespoon of frass left in the jar, they just decimated the leaves overnight.
I figured it would make a good addition to the worm bin and thought you guys might like to know about it. It seems to be a pretty useful byproduct.
Here's what AI says about it.
Whatâs in Frass?
Frass isnât just wasteâitâs a nutrient-packed byproduct:
Nutrients: Itâs rich in nitrogen (from the collardsâ proteins), plus phosphorus, potassium, and trace minerals like calcium and magnesium. Exact levels depend on what they ate, but collards make it pretty potentâthink of it as partially digested plant food with a nutrient boost.
Organic Matter: Itâs finely processed plant material, broken down by the larvaeâs guts into a form thatâs easier for microbes and worms to tackle than raw leaves.
Microbes: Frass carries gut bacteria from the caterpillarsâsome studies (like on other species) show it can include nitrogen-fixing or cellulose-breaking microbes. Itâs not sterile, so itâs a microbial starter kit.
Is It Good for Anything?
Absolutely! Hereâs what it can do:
Compost Accelerator: In any compost system, frass adds nitrogen and microbes, speeding up decomposition. Itâs like a turbocharge for breaking down your cardboard and food scraps.
Soil Amendment: Mixed into garden soil, it acts as a slow-release fertilizer. Studies on similar frass (e.g., from silkworms or black soldier flies) show it boosts plant growthâcorn and beans love it.
Worm Food: Worms, like red wigglers in a vermicompost bin, can process frass into high-quality castings. Itâs already pre-digested, so theyâll chow through it faster than tougher scraps.
Putting It in Your Worm Bin
Your idea to toss it in the worm bin for microbial activity is spot-on, but letâs weigh the pros and cons:
Pros
Microbial Boost: The bacteria in frass will kickstart activity, breaking it down further and feeding your wormsâ ecosystem. Itâs like seeding your bin with life.
Nutrient Rich: Worms love nitrogen-rich inputs. Mixed with your precompost (cardboard and collard stems), it balances the carbon-heavy cardboard, aiming for that 25:1 to 30:1 C:N ratio we talked about.
Fine Texture: Itâs already small and softâworms can handle it easily, turning it into castings quickly.
Cons and Cautions
Acidity: Frass can be slightly acidic (pH varies, often 5.5-6.5), depending on the collards and larval digestion. Worms prefer neutral to slightly alkaline (pH 6-8). Too much frass at once might sour the binâcheck with a pH strip if youâve got one, or just add it gradually.
Moisture: Itâs wetter than dry compost materials. With your already moist precompost (from kefir and food scraps), it could tip the bin toward soggy unless you balance it with more dry cardboard.
Heat Risk: Fresh frass has active microbes that might heat up as they decompose. Worms hate heat (above 85°F/29°C kills them). If itâs a lot of frass, let it sit a day or two in your precompost bin first to cool off.
Pest Leftovers: If any eggs or tiny larvae hitchhiked in the frass, they wonât survive the wormsâ digestion, but itâs worth a quick check to avoid surprises.
How to Use It
Hereâs a game plan:
Mix It In: Donât dump it all at once. Blend the frass with your precompost (that 18-gallon bin with cardboard and scraps). A handful or two per feeding is plentyâsay, 10-20% of what you add to the worms at a time.
Balance Moisture: If itâs wet and sticky, toss in extra cardboard shreds to keep the bin fluffy and aerobic. Aim for that wrung-out sponge feel.
Monitor: After adding, check the worms in a day or two. If theyâre clustering around it, theyâre happy. If theyâre fleeing to the edges, it might be too acidic or hotâadd more bedding (cardboard or coir) to buffer it.
Precompost First (Optional): If youâve got a ton of frass, let it break down in your precompost bin for a week first. The heat and microbes will mellow it out, making it worm-ready.
How Much Do You Have?
You said âa lotââif itâs just a few tablespoons from a couple larvae, itâs perfect for a small worm bin addition. If itâs cupsâ worth, precomposting it first might be safer. How many caterpillars are you raising, and how bigâs your worm setup?
Verdict
Frass is awesome for your worm binâgreat for microbes and nutrientsâjust donât overdo it straight off. Mix it smartly with your precompost, and itâll supercharge your vermicomposting.
