Ep 019: Beneficial Insects and VPD Control

0:00 — 0:27

Intro: two topics for today

Jeremy introduces episode 15 of the 10x10 series, teasing two topics: beneficial insects (which he is holding) and environmental control including a deep dive on VPD.

0:27 — 3:38

Predator mites (Stratiolaelaps / Hypoaspis miles)

Jeremy introduces two beneficial insects on hand: the nematodes and the predator mites (Stratiolaelaps scimitus, formerly known as Hypoaspis miles). He explains BuildASoil compost is not sterilised and arrives with predator mites already present, so buying them is optional but lets a grower 'set the pace' for the ecosystem rather than letting nature ramp up slowly. He invokes the permaculture principle that 'nature abhors a void'. He zooms in on the mites in the top dress so new growers don't freak out when they see them, notes there are also rove beetles in the bed, and that the nematodes are microscopic. He names Evergreen Growers as the supplier and says BuildASoil also offers them but it's easier to go direct during busy season. He mentions the mites come in a vermiculite carrier and that fast-moving mites are good while slow movers are decomposers working on the barley and kashi top dress.

1. 1. Note that predator mites and rove beetles are already present in BuildASoil compost from the top dress
2. 2. Optionally buy more from Evergreen Growers (google 'evergreen growers beneficial insects') to increase numbers and set the ecosystem pace
3. 3. Look for fast-moving mites in the top dress as confirmation they're there
4. 4. Don't confuse fast-moving predator mites with pest mites — the fast ones are good
5. 5. Accept that slow-moving mites are decomposers working on kashi / barley top dress

3:38 — 5:28

Applying predator mites to the beds

Jeremy walks over to the two halitosis plants in the Earthbox containers. One is in fresh 3.0 soil, the other is in recycled soil with a visible worm population. He sprinkles the vermiculite-carrier predator mites into the middle of each container, does all the vegetable containers too for defence 'everywhere' (kale, peppers), then puts the rest of the pack into the largest bed.

1. 1. Open the predator mite pack (vermiculite carrier)
2. 2. Sprinkle into the centre of each container and let them run around
3. 3. Dose every container including vegetables (kale, peppers) for full-room defence
4. 4. Put the remainder of the pack into the largest bed

5:28 — 9:32

Applying beneficial nematodes

Jeremy pulls out the nematode bag and explains these are the good kind — beneficial nematodes that target fungus gnat larvae and other pests. He justifies the ~$100 two-pack as a good investment for long-term no-till beds because the soil stays moist between cycles and the predators persist. He demonstrates the application: the nematode pack stores in the fridge (the mites stay at room temperature); the powder is not water-soluble so he puts water in the watering can first, then adds the nematode powder, shakes it continuously, removes the fan-spray nozzle from the wand, and spot-waters each root zone rather than mixing into full irrigation volume. He warns not to mix ahead — use them immediately — and not to drop the sprayer on your toe if wearing sandals.

1. 1. Store nematode pack in the fridge; store predator mites at room temperature
2. 2. Put the water in your watering can first (about a gallon and a half)
3. 3. Dump all the nematode powder into the water
4. 4. Shake continuously to keep the powder in suspension
5. 5. Remove the fan-spray nozzle from the wand — you want a stream, not a spray
6. 6. Pump and dispense a small volume into each root zone across every container
7. 7. Don't try to water for plant need — just aim for even distribution of the nematodes
8. 8. Err on the side of caution; worst case, go around twice
9. 9. Use them right away — don't mix the batch and save it for tomorrow
10. 10. Watch your toes — don't drop the sprayer on them

9:32 — 12:50

Environment and VPD introduction

Jeremy pivots to environmental control. He notes Colorado is very dry (10-15% ambient humidity) and says growers elsewhere may need to dehumidify instead. He introduces the philosophy of addressing the weakest environmental link first before optimising. He points out the humidifier running and the Niwa Grow Hub smart power strip on the wall, which is reading humidity, temperature and (basic) light, then controlling the exhaust fan and humidifier against a VPD-derived recipe. He explains monitors vs controllers: monitors alert you; controllers act for you.

12:50 — 18:16

VPD theory — stomata, CO2 and light intensity

Jeremy explains vapor pressure deficit: the plant opens its stomata to take in CO2 and breathe, and under bright lights this can dry the plant out if ambient humidity is too low. Higher temperature needs higher humidity so the plant doesn't stress. He stresses that leaf surface temperature matters more than room temperature — under HPS with glass hoods the leaf is elevated above room temp; under LEDs the leaf can actually be about two degrees below ambient because LEDs dump heat out the back through heat sinks. He recommends a kitchen laser thermometer to measure leaf surface temperature and offset the VPD chart accordingly. He describes the chain of adjustments: if you turn up light intensity and temperature, you need to turn up humidity and then CO2 to keep VPD in the green zone. In living soil he doesn't dose CO2 — fresh air exchange is the CO2 source — so if you can't add CO2, just back the light intensity down a bit. In dry Colorado, hitting a target VPD by raising humidity and cranking lights can double or triple veg speed compared to lights-dimmed-for-comfort.

1. 1. Look up a VPD chart and find the green zone
2. 2. Measure room temperature and humidity
3. 3. Measure leaf surface temperature with a kitchen laser thermometer
4. 4. Offset the chart reading for leaf-vs-room delta (positive under HPS, roughly -2 under LED)
5. 5. If light intensity goes up, raise humidity to compensate
6. 6. If you can't add CO2, back the light intensity down instead of pushing harder
7. 7. Address the weakest environmental link first before optimising further

18:16 — 22:14

Monitoring tools: thermo-hygrometer, Pulse One and Pulse Pro

Jeremy walks through monitoring hardware. He starts with a basic temperature-and-humidity meter with min/max recall — the cheapest way to find out if your grow room ever got too cold (e.g. 30F in a garage) or too hot (over 100F under lights), and therefore what weakest link to fix first (heater, exhaust, AC). Then he shows the Pulse One and the newer Pulse Pro, which Pulse just sent him. The Pulse Pro adds CO2 monitoring and PAR monitoring on top of the Pulse One's temperature, humidity and VPD; he cites it as around $500 off, and notes a standalone CO2 meter alone is $100-$200 and the Apogee PAR meter is $538, so the Pro starts to pay for itself. It's Wi-Fi (2.4GHz), clips on a carabiner in the canopy at leaf height, and emails/texts alerts if humidifier runs out of water, but it does not control anything — it only monitors.

22:14 — 26:29

Niwa Grow Hub smart power strip

Jeremy then walks through the Niwa Grow Hub — around $200, a Wi-Fi smart power strip that actually controls (not just monitors) the room. He explains the 15A / 120V limit means he runs two of them: one on the 2x2, one on the 10x10, with a three-way plug for the lights. You set a recipe per cycle (veg/flower) with lighting schedule and climate targets, then it turns humidifier, fan, lights and even a drip system on and off automatically. Jeremy's flower 10x10 recipe is 80F / 55% humidity during stretch (lower humidity to drive transpiration), with a lower night-time temperature setpoint so the fan runs during lights-off to keep humidity down and prevent bud rot. He shows the app live: lights on, fan on, humidifier off, 85.6F and 49% RH with the fan working to bring temperature back below 85F and the humidifier just kicking on as humidity dropped below 50%. He contrasts this to manually using digital 15-minute timers to cycle an exhaust fan (e.g. 15 on / 15 off) to target a humidity range in a tent without a controller.

1. 1. Buy one or two Niwa Grow Hub units (each limited to 15A / 120V)
2. 2. Plug the humidifier, fan, and lights (via a three-way splitter) into the strip
3. 3. Set a lighting schedule (e.g. 6am-6pm for flower)
4. 4. Set a day climate recipe (Jeremy uses 80F / 55% RH for stretch in flower)
5. 5. Set a lower night-time temperature setpoint so the fan runs to vent humidity
6. 6. Set the humidifier target lower at night so it doesn't fire during lights-off
7. 7. Watch the app to confirm automatic correction (fan kicks on above setpoint, humidifier kicks on below target)
8. 8. Alternative with no controller: use a 15-minute digital timer to cycle an exhaust fan on/off to target a humidity range

26:29 — 29:32

PAR measurement and closing

Jeremy shows his Apogee quantum flux (PAR) meter — around $538 — and explains it's worth the money because he shares numbers publicly and needs them to be accurate. He plans to compare the Apogee reading against the Pulse Pro's built-in PAR in the next episode. He explicitly rejects phone-camera PAR apps — he's had 'horrible results' with them and does not recommend them. For home growers who don't want to buy a PAR meter, he suggests checking the manufacturer's published PAR-at-12-inches and PAR-at-24-inches for your grow light and setting distance accordingly, then reading plant health. He closes by reiterating that BuildASoil isn't trying to sell any of these specific products — buy whatever tool gets you to a target VPD — and reminds viewers to support their local business. He notes he usually applies beneficials on the day the soil is mixed or finishes cooking, but this round was delayed due to busy season. He recommends the Pulse website as a source for a free VPD calculator and chart maker.