How's this for a sequel to my book – Indoor Salad - How Not to Grow Pests Indoors.
I had a chapter on Problems in my original outline. But the book was too long. The topic was discouraging. The pests are regional. So I dropped the chapter and just worked some suggestions into other material. But the problem remains, and I've received questions from readers.
When you grow vegetables indoors, you welcome a living breathing procreating ecosystem into your home. For better and for worse. It's natural to focus on the downside – bugs and slimes, ick! There is an upside, though. As natural animals, we weren't designed to live in a chemical-laced clean room. The war on germs undermines our own immune systems, contributing to rising rates of diabetes, allergies, and asthma, among other things. (The "hygiene hypothesis"1.)
I love the origin of the word "disaster" – to be torn from the stars. It's even more disastrous to be torn from our own ecosystem. Pets keep you healthier 2. Everyone agrees that lapping waves, or a beautiful sunset, or a lovely view, is soothing. Lovely plants clean the very air you breathe. These links to the web of life say, You belong here. With us.
Granted, we don't feel that way about aphids and algae. And if you're already allergic to mold, extra exposure doesn't help.
Today's Guest Pest: The Slimes
What I'm calling a "slime" is a microorganism grown out of control. But note the 'out of control' part. There's nothing wrong with microbes. Your own body contains 10 times more microbes than human cells3. (It's OK. Your cells are much bigger.) How do the slimes arrive in your life? Simple. They're already here. They're airborne, and soilborne. They've always been here, and always will be. Microbes ruled the Earth for billions of years before the seed was invented.
Typical slimes include algae, fungus, molds, mildews, and many kinds of bacteria. Yeah, I know – ick, ick, ick! The gross-out quotient is high. But remember – they're always here. We just want fewer of them in a particular spot.
So how do we persuade these omnipresent beings to our way of thinking? Well, turn that around. What persuaded them to reproduce so much?
Algae – green slime. Likes light, water, and fertilizer.
Fungus and bacteria – fuzzy or slimy patches, white, cream, and grey. Likes dark, water, and fertilizer.
Things they don't like:
Bleach – will kill anything, including your plant and skin cells on your fingers. Always use diluted, and never on a plant or its roots. This is for washing equipment between grows.
Detergent and soap – gentler yet less authoritative than bleach. Can use diluted on leaves.
Hydrogen peroxide. Use diluted 1 part in 5 for dabbing slimes off soil or sponge surfaces.
Fresh air – good air circulation helps keep soil and leaves dry.
So, start clean. And if the slimes get out of hand to the extent you want to start over, clean with authority – use diluted bleach. Most tap water already has very dilute bleach in it (that familiar chlorine smell). For hydroponics, rinsing with tap water once a week can help keep microbe populations in check.
To prevent algae, block light from wet nutrient-rich surfaces, with mulch or a simple piece of paper. Pretty as it might be to have a glass reservoir, that's just asking for algae growth. Hydroponic reservoirs need to block light. Once a week or so, you could add a few drops of hydrogen peroxide to the water. Once algae gets to the visible green slime stage on soil surfaces or grow sponges, I start by scraping it off. Then I dab it off with dilute peroxide on a paper towel or Q-tip. Don't live and let live with an algae outbreak – in most cases, it needs to go. It poisons your plants, and leads to secondary slimes and insects.
Leaf fungus is usually a tomato problem, and to some extent, it's a war between the plant and the fungus. If you can see the fungus, the plant is losing. To prevent fungus on leaves, provide air circulation, leave space between plants, and prune so air can flow through. Prune off bottom branches to keep leaves away from the soil. If you can see fungus patches, prune off the affected leaves, and remove any yellow leaves. You can try a fungicide after pruning, to slow fungus spread – there are organic formulas. If you have other tomato plants to protect, you might want to sacrifice the infected plant. But my usual strategy is to let the tomato live with the infection, and keep sick leaves pruned. Because tomato plants almost always get sick with something. They usually still produce good fruit. If they don't, or the fruit is bad, or the plant is too young to be worth saving, then I dispose of the plant.
Hydroponic water slimes are probably bacterial. Rinse with tap water. Try a bit of peroxide in the refill. If it gets too gross or smells bad and rinsing doesn't control it, you may need to dispose of the plant.
Soil fungus and bacteria are supposed to be there. Some of them can kill seedlings, and that's sad. You can try using sterile seedling mix – but it won't stay sterile. Usually the best strategy here is to keep the seedlings themselves happy and well-lit, not too wet, not too dry, not too crowded, with plenty of air, and the right temperature range. Use minimal fertilizer – seeds don't need much. If a seedling grows fast and robust, soil microbes won't kill it.
Too much water, and too much fertilizer, harm the plant and feed the microbes. Try to only water from the bottom, and let the soil surface dry between waterings.
I hope that helps! Please let me know in the comments – would you like more blog-episodes on the pests?
What's Growing Now?
Currently harvesting two varieties of cucumber, lettuce, mustard greens, and senposai (an Asian brassica). Tomatoes and eggplant ripening on the vine. My early indoor/outdoor pepper has flower buds, for harvest starting indoors in March or April. I just planted a couple more late indoor/outdoor peppers, for outdoor harvest starting in May or June.
What are you growing now?