Sooner or later, every grower gets bugs. You can have a sealed tent, filtered air and a spotless routine, and they'll still find a way in. They come in on clones, on your clothes, from your pets, on the bag of soil that sat in the shed all winter. You can't stop them ever arriving, but you can decide whether they get a week to settle in or a month.
Here's what we see most often in tents, and what we'd do about each one.
Check your plants before you think you need to
Most people find pests when the damage is already obvious. Get in the habit of a proper look once a week. Flip the leaves over, check the new growth at the tops, and look where leaves meet stems. A bit of magnification helps too. A Microscope is money well spent if you want to see what's actually going on.
Hang a few Yellow sticky traps around canopy height too. They won't cure an infestation, but they tell you what's flying around in there, and they're often the first clue that something's wrong.
Spider mites
The one everybody dreads. You'll usually notice tiny pale speckles on the tops of the leaves first, almost like someone's dusted them. Then the leaves yellow, and if it's gone too far you'll see fine webbing. Flip a leaf and the culprits are underneath, tiny and moving.
Mites breed fast, and the warmer your tent runs, the faster they go. In a hot tent a whole generation can go from egg to egg-laying adult in under a week. They also hide well in tent seams, pot rims, pole joints and the gaps in shelving. Some go dormant between crops, which is why mites so often turn up in the same corner every single run.
Eggs survive most sprays, so one pass won't do it. You have to spray, then spray again a few days later to catch the newly hatched ones before they mature and lay more. Do that a few times in a row and you break the cycle. Coverage matters more than anything. Hit the undersides of the leaves, the stems, and every surface you can reach, not just the tops of the plants.
For this we'd reach for Osmoslay. It works physically rather than as a chemical poison, which matters with mites because they build up resistance to chemical sprays quickly. Green Cleaner Plant Wash is another good option (More on both below).
Fungus gnats
Small dark flies hovering around the base of your plants or wandering across the surface of the medium. The adults are mostly just annoying. The real damage comes from the larvae, which live in the top layer of damp growing medium and chew on fine roots. Seedlings and freshly rooted clones get hit hardest.
Nearly every fungus gnat problem starts with a medium that stays wet. If the top layer never gets a chance to dry out, you've basically built them a nursery. Back off the watering a little and let the surface dry between feeds, or better still, try bottom watering. Use yellow sticky traps to knock down the adults.
For the larvae, VectoBac Fungus Gnat Control is a bacteria-based treatment you water into the medium. It targets the larvae, which is where you actually want to hit them.
Aphids
Soft little insects that clump together on new growth and stems. You'll often spot the white cast skins they leave behind before you spot the aphids themselves, plus a sticky residue on the leaves (honeydew). If that's left alone, a black sooty mould can move in on top of it.
The good news is that aphids don't lay eggs. They give birth to live young, so there's nothing hiding from your spray. A thorough coverage followed by a repeat a few days later usually sorts them. The bad news is how fast a few become a few hundred, so don't wait.
Whitefly
Give the plant a gentle shake. If a little cloud of tiny white flies lifts off, that's whitefly. They also leave honeydew, and they're a pain because both the egg and pupal stages shrug off most sprays.
So this one's a longer game. Use Yellow sticky traps to cut down the adults, and spray repeatedly over a couple of weeks so you catch each new wave as it hatches. Stopping the moment things look better is the classic mistake. Keep checking until you genuinely can't find any.
Thrips
Thrips are hard to see, which makes them sneaky. You're more likely to notice the damage: silvery streaks or flecks on the leaves, sometimes with tiny dark dots. Same approach as the others. Sticky traps to monitor, repeated sprays to break the cycle, and a good look under magnification to confirm what you're dealing with.
Keeping them out in the first place
A few habits that make a real difference:
- Quarantine new plants. Anything new, especially clones from a mate, should sit somewhere else for a week or so before it goes in your tent.
- Clean between runs. Wipe down the walls, poles, floor and pots. Mites love the gaps you didn't wipe.
- Mind what you bring in. If you've been out in the garden, wash your hands and maybe change your top before you go near your plants.
- Keep the air moving. Stagnant air suits pests and mould. A decent Fan makes a difference, and so does keeping humidity in check.
A few spraying tips
Spray when the lights are about to go off (or are off) so leaves can dry and you don't scorch anything under a hot light. Always read the label. Test on a leaf or two first if you're using something new. And once you're into flower, be careful about what goes on the plant avoid products like Abamectin or Mavrik Insect Sprays.
Product recommendations
Osmoslay
Osmoslay is an ultra-concentrated spray that interferes with a pest's ability to control its own water balance. It elimantes all soft bodied insects including mites by physical action rather than poison, and there are no reports of resistance, which is a big deal with mites. It works on soft-bodied pests like mites, aphids and thrips, and it leaves no residue, so it's gentle enough for house plants too. It doesn't kill eggs, which is why the repeat sprays matter. The Starter Kit comes with a trigger bottle with volume marks and a syringe loaded with enough concentrate to make 2 litres of spray. Mixing 0.1ml per 200ml of water. Mix it fresh and use it within a couple of days, because diluted Osmoslay breaks down. When you're ready to top up, the Refill Pack is the most cost effective solution. Safe to use up to day of harvest.
Green Cleaner Plant Wash
Green Cleaner is a concentrate designed to dehydrate and suffocate pests on contact, including larvae and eggs. It's a handy one to have if you're also fighting powdery mildew, since it's made for mites, aphids, thrips, whitefly and fungus gnats as well as mildew. It fits into an IPM routine and can be used from start through to harvest. It's natural and safe to use around people, pets, soil and food. Add the water to your spray bottle first, then the Green Cleaner, and saturate the plant properly. The label has rates for clones, maintenance sprays and heavy infestations, so you're not guessing. Safe to use up to day of harvest.
Herbi Zymes All Natural Pest Control
Herbi Zymes is made from fermented plants and fruits with Bacillus thuringiensis added. It's biodegradable and controls whitefly, mites, fungus gnats, fruit flies and other soft-bodied insects. It also triggers the plant's own defences and helps nutrient uptake, it even helps with powdery mildew too! The Pre-mixed 500ml is the grab-and-spray option, ideal for a small tent or a regular preventative mist. If you're doing bigger jobs, the concentrate works out cheaper and can be used as a spray or a soil drench. For an infestation, the maker's schedule is to spray three days in a row, then weekly until you can't find any pests. Make sure the spray makes full contact with the pests, eggs and larvae.
Whichever you choose, stick with one product for a full round of treatments rather than mixing and matching.
You can see the whole range in our Pest Control Collection on our website. If you're not sure what you're looking at, give us a call on 027 295 6833 or pop in to see us at 5 Burton Street, New Plymouth.