Eastern Cape Fancy Lettuce DWC

Production, Nutrition & IPM Plan

Locked-specs version. Companion to the Partnership Proposal. Replaces prior generic plant-ops draft.

Prepared by Richard Buschagne, YBA Group — 2026-05-06

What’s in this document

This is the operational playbook for the fancy lettuce side of the operation, sized to your exact facility and your exact cadence. Three sections, all written to be used together:

1. Production Plan — five locked cultivars, the 8-6-2 board pattern, weekly math at every capacity tier, the 6-week tunnel rotation, daily and weekly cadence
2. Hydroponic Nutrient Solution + Mixing Plan — full A-tank / B-tank recipes from raw salts (or SA-available pre-mades), per-stage EC and ppm targets, mixing protocol, foliar Cal-Mag tip-burn prevention
3. IPM — Preventive + Reactive Spray Plan — every relevant pest and disease for SA lettuce production, both chemical and organic options for prevention and reaction, 4-week rotating preventive calendar, resistance management, application protocol

A note on scope: the system is aquaponics-ready, but fish are out of scope until next year. This plan treats the operation as pure hydroponic DWC for now. Where a product would need to be swapped out before fish go in (copper, abamectin, certain neonicotinoids), that’s flagged in the IPM section so the future transition is clean.

A note on doctrine: engineered for safety, operated for precision, projected conservatively, delivered above expectation. All critical systems sit at 200 % of needed capacity. We operate at 50–80 % of engineered ceiling. The plan ramps from 40 % output to 100 % over five months — only stepping up when sales prove the previous tier.

1. Production Plan

1.1 Cultivar Selection — The Five You Plant Every Week

Five cultivars, all SA-available, all proven in DWC, all premium-pricing in retail and HORECA channels.

All five tolerate Eastern Cape coastal conditions; summer heat-tolerant fallback options listed in §1.7.

1.2 The 8-6-2 Board Pattern — Master Layout

Every board planted goes in this exact pattern. No exceptions. This consistency is what makes the rotation calendar and the harvest sales sheet predictable.

Per section: 96 boards × 16 plants = 1,536 plants Per tunnel (2 sections): 3,072 plants Full facility (12 sections): 18,432 plants standing

1.3 Weekly Math at Full Capacity (100 %)

At full rotation: harvest 1 tunnel/week (2 sections, 192 boards, 3,072 heads moving out the door each Friday). Here’s exactly what feeds that pipeline:

Seed 16 trays Monday → transplant the cohort that finished its 3–4 week nursery on Wednesday → harvest Friday. Same numbers, every week, forever.

1.4 Capacity Ramp — Months 1 to 6

Don’t switch on all 6 tunnels day one. Build demand and operations in lockstep. Each step up only happens when the previous month’s output is reliably sold.

1.5 The 6-Week Tunnel Rotation Calendar

Once at full capacity, every week one tunnel is harvested-and-replanted, while the other five are at staggered points in the 6-week DWC grow-out. The system is a wave that never stops.

Every Friday, one tunnel comes out. Every Wednesday, one tunnel goes in. The nursery is always running 3–4 weeks ahead of transplant day.

1.6 Daily + Weekly Operational Cadence

The coolest-window rule is non-negotiable. Lettuce stresses fast in heat — transplant shock and post-harvest wilt both halve in cool conditions.

Eastern Cape coolest windows:

• Summer (Oct–Mar): 04:30 – 07:30
• Winter (Apr–Sep): 06:00 – 09:00

Weekly rhythm (full capacity)

At 40 % (Month 1) the rhythm is identical, just smaller numbers — 7 trays Monday, 77 boards transplanted Wednesday, ~1,228 heads harvested Friday. Build the discipline of the cadence first; the volume scales into it.

1.7 Risk + Flex Notes

Cultivar fail-safes

Seasonal rotation (Eastern Cape)

• Summer (Oct–Mar): Lean to heat-tolerant cultivars — Rex butterhead, Oak Leaf Red, Concept Red, Parris Island Cos. Tip-burn risk rises above 28 °C; manage with shade cloth, evening misting, increased calcium foliar
• Winter (Apr–Sep): Full Salanova lineup performs at peak. Lollo Rossa colour deepens. Slightly slower DWC stage — budget 6.5 weeks instead of 6

Capacity-ramp triggers (objective signals to add the next tunnel)

Step up to next month’s capacity only when all three are true for 4 consecutive weeks:

1. Standing weekly orders ≥80 % of current month’s plant output
2. Cold-chain + packing keep up without overtime or product loss
3. Cash position covers at least 6 weeks of operating cost at the new capacity level

If any one signal fails, hold current capacity another month and address the bottleneck before scaling. Every tier is profitable on its own.

1.8 Quick Reference Card — Print and Pin to the Wall

• 5 cultivars, 1 board pattern: 4 Lollo Rossa, 4 Salanova Red, 3 Butterhead, 3 Salanova Green, 2 Cos
• Full capacity weekly: 16 trays Monday, 192 boards Wednesday, 3,072 heads Friday
• Cool windows only: 04:30–07:30 summer, 06:00–09:00 winter
• One tunnel out, one tunnel in, every week
• Ramp: 40 % → 55 % → 70 % → 85 % → 100 % across Months 1–5
• Trigger to scale: 80 % of output sold on standing orders, 4 weeks running

2. Hydroponic Nutrient Solution + Mixing Plan

This is the locked nutrient blueprint for the fancy lettuce production line. Pure hydroponic — every nutrient comes from synthetic fertiliser salts dissolved into the water. Two-tank system (A + B + acid + base), per-stage dosing, daily water-quality discipline.

2.1 Target water quality (root zone, DWC pool)

These are the four readings to check every morning. A R600 combo meter (EC + pH + temp) does the job; dissolved oxygen needs a separate DO meter.

EC targets per stage:

2.2 Macronutrient targets (mg/L = ppm)

2.3 Micronutrient targets (mg/L)

Same levels at every stage.

A chelate is a molecule that wraps around a metal ion (like iron) and protects it from precipitating out of solution. EDDHA is the strongest, most pH-tolerant chelate available.

2.4 Two-Tank System Recipe (A + B + acid + base)

We mix as a two-part concentrate. Calcium nitrate goes in Tank A on its own. Everything else goes in Tank B. Never combine A and B at concentrate strength — calcium and phosphate/sulphate react instantly into a chalky white sludge and the fertiliser is wasted.

These recipes make 100× concentrate stocks (10 L stock → 1000 L working solution). Adjust dosing pumps or measuring jugs accordingly.

Tank A — “Calcium Tank” (per 1000 L stock concentrate, 100×)

Tank B — “Everything Else Tank” (per 1000 L stock concentrate, 100×)

Working tank dilution per stage

To make 1000 L of working nutrient solution:

pH adjusters

Always wear gloves and eye protection. Both are caustic.

2.5 Pre-made Commercial Alternatives (SA-available)

If you’d rather not mix from raw salts, three SA-available pre-blended options work well:

Even with pre-mades, always supplement Iron-EDDHA separately at 2 g per 1000 L — most pre-blends use cheaper EDTA chelate which fails above pH 6.5.

2.6 Stock Tank Mixing Protocol

Mix concentrates in food-grade HDPE tanks, opaque (block sunlight — algae loves nutrient solution), tight lids. Each tank gets a labelled “A” or “B” sticker. Never swap dosing tools between them.

Tank A mixing order

1. Fill tank to 80 % with clean water (room temp, ~22 °C)
2. Start agitator (or stir vigorously by hand)
3. Add calcium nitrate first — dissolve fully (5–10 min, water turns clear)
4. Add Iron-EDDHA — water turns deep wine-red. Normal.
5. Add potassium nitrate — dissolve fully
6. Top up to 1000 L mark
7. Agitate 15 min, label with mix date

Tank B mixing order (sulphates before phosphates prevents lump formation)

1. Fill tank to 80 % with clean water
2. Agitator on
3. Add magnesium sulphate (Epsom) first — fast dissolve
4. Add potassium sulphate — dissolve fully
5. Add trace elements (Mn, Zn, Cu, B, Mo) one at a time. Pre-dissolve each in 5 L of warm water before pouring in — they’re tiny amounts, clump easily
6. Add monopotassium phosphate (MKP) — dissolve fully
7. Add potassium nitrate last
8. Top up to 1000 L, agitate 15 min, label

Storage: cover, dark, cool (under 25 °C), labelled with mix date. Use within 30–60 days max.

2.7 Working Tank Preparation (the actual DWC pool)

1. Test source water first. Should be below 0.4 mS/cm EC. Higher = less nutrient room. If source EC > 0.4, switch to rainwater or RO
2. Fill tank to working volume with potable water
3. Run air stones for 30 min before adding nutrients. Aeration also drives off chlorine in municipal water
4. Add Tank A first (per stage table). Agitate 5 min. Water turns slight red-tint from iron
5. Add Tank B (per stage table). Agitate another 5 min
6. Adjust pH down with phosphoric acid. Add slowly — 10 mL at a time per 1000 L, agitate, retest. Target 5.8–6.2
7. Final readings — EC at target for stage, pH 5.8–6.2, water temp 18–22 °C, DO 6–8 mg/L. Log on tank sheet
8. Hold 30 min, retest. If readings stable, plants go in

2.8 Daily + Weekly Nutrient Management

Every morning (before 09:00):

• EC check — log
• pH check — log
• Water temp — log
• DO check — log
• Visual root inspection through a sample board — white roots = healthy, brown/slimy = Pythium alarm

Daily top-up: Plants drink water faster than they uptake nutrients. As volume drops, EC rises (concentration effect). Top up with plain water to restore volume. Only add fresh concentrate if EC stays below target after top-up.

Weekly drain-and-refresh: Every 2–3 weeks, fully drain DWC tank, scrub interior with 1 % hydrogen peroxide, rinse, refill from scratch. DWC accumulates root exudates and pH buffers drift. Fresh tanks = fresh growth.

Sensor calibration: Once a week — calibrate EC meter against 1.413 mS/cm standard, pH meter against 4.0 + 7.0 buffers. A drifted meter is worse than no meter.

2.9 Foliar Cal-Mag + Tip-Burn Prevention (lettuce-specific)

DWC roots do most of the eating, but calcium doesn’t move well inside the lettuce plant once absorbed. Young growing leaves at the heart of the head can starve for Ca even when root-zone Ca is fine — that’s tip-burn. The fix is to spray Ca directly onto the leaves where it’s needed.

Foliar schedule

Foliar application rules — the never-do list

• Never spray when leaf temp >26 °C — droplets concentrate as they evaporate, leaf burn
• Never spray with sun directly on leaves — droplets focus light, spotted scorch
• Never tank-mix foliar nutrient with chemical pesticide unless label explicitly compatible
• Always agitate continuously — Cal-Mag settles fast
• Always test on 5 % of crop for 48 hr if new product (red Salanova more sensitive than green Butterhead)

Calcium tip-burn — the #1 lettuce production failure

What it is: brown, papery, dead tissue on the young inner leaves of the lettuce head — leaves closest to the growing tip. Affected heads are downgraded — cannot be sold to retail.

Why it happens: Ca moves through the plant only with the transpiration stream (water flow from roots to leaves driven by leaf evaporation). Young inner leaves transpire less than outer leaves because they’re shaded and humid in the heart. Even when root-zone Ca is at 180 ppm, the inner leaves run short. Trigger conditions:

• High humidity (transpiration drops)
• Fast growth phase (Ca demand spikes)
• Hot afternoons + cool nights (transpiration whipsaws)
• High EC at maturity (osmotic stress on roots)

Prevention protocol:

1. Airflow — tunnel side-vents open whenever outside temp permits. Fans on if humidity >80 %
2. Moderate EC at maturity — don’t push above 2.0 in the final two weeks
3. Weekly Cal-Mag foliar — non-negotiable from DWC week 1 onwards
4. pH discipline — drift above 6.5 locks out calcium even at correct ppm
5. Cooling — if water temp creeps over 23 °C, deploy chillers or shade cloth

Early symptoms to catch: faint translucent edges on youngest inner leaves, slightly cupped young leaf tips, brown speckling along leaf margin (early).

Recovery: not possible. Tissue is dead. Affected heads are downgraded or culled. Prevention is the only strategy.

2.10 Weekly Nutrient Management Checklist

Daily (every morning before 09:00):

• EC reading logged for every active DWC tank
• pH reading logged for every active DWC tank
• Water temp logged
• Dissolved oxygen logged
• Visual root health check on one sample board per tank

Weekly (Monday morning):

• Calibrate EC meter (1.413 mS/cm) and pH meter (4.0 + 7.0 buffers)
• Foliar Cal-Mag spray applied on every block at correct stage dose
• Stock tank levels checked — re-mix if below 200 L
• Tunnel ventilation, fans, chillers tested
• Pre-harvest tanks: confirm 5-day plain-water flush in progress

Every 2–3 weeks per tank:

• Full drain, scrub with 1 % hydrogen peroxide, rinse, refill from scratch
• Source water EC retested — confirm still under 0.4 mS/cm

3. IPM — Preventive + Reactive Spray Plan

3.1 The IPM Philosophy

Integrated Pest Management is the discipline of preventing pest and disease problems before they occur, rather than reacting after damage is visible. In a DWC tunnel system, prevention is everything. Once Pythium enters the nutrient tank or downy mildew sets up in the canopy, you are no longer growing lettuce — you are managing a crisis. The cost difference between prevention and reaction is roughly 1:10. A R200 weekly preventive spray beats a R2,000 reactive treatment plus crop loss every single time.

Five pillars:

1. Prevention beats reaction — follow the rotating preventive calendar (§3.3) every week, no exceptions
2. Organic preferred where it works — lead with biologicals (Beauveria, Bacillus, neem); escalate to synthetic chemistry only when thresholds breached and biologicals failed
3. Rotate active ingredients — never the same mode of action two weeks running
4. Document everything — every spray, every count, every observation goes into the log (§3.7)
5. The spray-application log is mandatory — no spray happens without a written record

Jargon legend: PHI = Pre-Harvest Interval (min days between spray + harvest). REI = Re-Entry Interval (min hours before staff may re-enter). MoA = Mode of Action. IRAC / FRAC = Insecticide / Fungicide Resistance Action Committee group codes.

3.2 Comprehensive Pest + Disease Catalogue

Each entry covers: appearance, conditions favoured, chemical prevention + organic prevention + chemical reactive + organic reactive, plus cultural controls.

3.2.1 Aphids (Myzus persicae, Macrosiphum euphorbiae, Nasonovia ribisnigri)

Look: Small (1–3 mm) green, pink, black soft-bodied insects on leaf undersides + growing tips. Sticky honeydew below colonies; sooty mould may follow. Nasonovia is the lettuce-specialist — hides deep in the heart, hard to spot until packing.

Favoured: 18–25 °C, low humidity, sheltered tunnel air. Spring + autumn peaks.

Cultural: Yellow sticky traps every 10 m. Release Aphidius colemani parasitoid wasps (Real IPM) at first sighting — 1 wasp/m². Strip and destroy heavily infested plants. Ant control on tunnel perimeter (ants farm aphids).

3.2.2 Whitefly (Trialeurodes vaporariorum — Greenhouse Whitefly)

Look: Tiny (1.5 mm) white moth-like insects fluttering up in clouds when canopy disturbed. Yellow nymphs + pupae glued to leaf undersides. Honeydew + sooty mould lower leaves.

Favoured: 22–28 °C, sheltered tunnel air, year-round in EC tunnels.

Cultural: Yellow sticky traps. Insect-mesh on tunnel vents (≤0.6 mm aperture). Release Encarsia formosa parasitoid wasps at 3/m² when traps show >5 adults/trap/week.

3.2.3 Western Flower Thrips (Frankliniella occidentalis)

Look: Tiny (1–2 mm) slender yellow-brown insects scrape leaf surface. Silvery-white streaks with black faecal flecks. Vector for Tomato Spotted Wilt Virus (TSWV) — serious risk.

Favoured: 25–30 °C, dry air, summer.

Cultural: Blue sticky traps (thrips prefer blue) — min 1 per 50 m². Release Amblyseius cucumeris predatory mites at 100/m² preventively. Remove flowering weeds inside + within 5 m of tunnel.

3.2.4 Two-Spotted Spider Mite (Tetranychus urticae)

Look: Pinprick (0.5 mm) yellow-green mites with two dark spots, leaf undersides. Stippled/bronzed leaf surface; fine webbing in heavy infestations. Use 10× hand lens.

Favoured: Hot dry — 27–32 °C, <60 % RH. Summer + any time tunnel humidity drops.

Cultural: Raise tunnel humidity above 65 % during hot spells (overhead misting on timer). Release Phytoseiulus persimilis predatory mites at 10/m² at first sighting — extremely effective on lettuce. Avoid broad-spectrum pyrethroids — wipe out predators, trigger mite blooms.

3.2.5 Leafminer (Liriomyza spp.)

Look: Small (1.5 mm) black-and-yellow flies. Larvae produce silvery serpentine tunnels (mines) inside leaves — diagnostic. Cosmetic damage destroys fancy-lettuce sale value.

Favoured: 20–28 °C, year-round in EC tunnels.

Cultural: Yellow sticky traps. Release Diglyphus isaea parasitoid wasps at first mine sighting. Strip and incinerate mined leaves — never compost.

3.2.6 Caterpillars (Loopers, Cutworms, Spodoptera armyworm)

Look: Loopers — green, “loop” as they crawl, chew round holes; Cutworms — fat grey-brown, sever stems at raft level overnight; Spodoptera — banded green-brown, voracious, gregarious when small. Frass (caterpillar droppings) is the giveaway.

Favoured: Spring through autumn; moth flights peak warm humid evenings.

Cultural: Pheromone traps for Spodoptera + Helicoverpa — gives 7 d warning. Hand-pick large caterpillars in early evening. Insect mesh on vents.

3.2.7 Slugs + Snails

Look: Irregular ragged holes in leaves, slime trails on rafts + floors, hide under raft edges + damp corners. Active overnight.

Favoured: Cool wet conditions, autumn + winter, high humidity in tunnels.

Cultural: Copper tape on raft edges + tunnel doorways — slugs will not cross copper. Eliminate hiding spots: clear weeds, lift debris, dry floor edges. Beer traps in corners.

3.2.8 Fungus Gnats (Bradysia spp.) — nursery hazard

Look: Small (2 mm) dark mosquito-like flies hovering above seedling trays. Larvae are clear-bodied with black heads, in damp media. Chew young roots + vector Pythium.

Favoured: Wet seedling media, warm nursery, organic substrate.

Cultural: Let seedling tray surfaces dry between irrigations. Yellow sticky traps at media level. Strict nursery hygiene — sterilise trays between batches.

3.2.9 Downy Mildew (Bremia lactucae) — #1 lettuce killer in cool/wet conditions

Look: Pale yellow blotches on upper leaf surface, with fluffy white-grey sporulation on underside in matching patches. Older lesions go brown/necrotic. Spreads across a tunnel in 48 hours.

Favoured: 10–18 °C nights, leaf wetness >4 h, >90 % RH. EC winter is prime Bremia weather.

Cultural: Maximise airflow — open vents early, run circulation fans. Avoid overhead irrigation. Wide plant spacing for fancy lettuce. Source Bremia-resistant cultivars (BL designation, e.g. BL 16-37). Remove infected plants in sealed bag.

3.2.10 Powdery Mildew (Erysiphe cichoracearum)

Look: White powdery patches on upper leaf surface, eventually coalescing. Infected leaves yellow + senesce.

Favoured: 20–28 °C, moderate RH (40–70 %), poor airflow. Late summer/autumn.

Cultural: Improve airflow. Avoid excess nitrogen (lush growth = mildew bait). Wider spacing. Sulphur burns lettuce above 28 °C — never spray sulphur summer midday.

3.2.11 Sclerotinia / Lettuce Drop (Sclerotinia sclerotiorum)

Look: Lower leaves wilt + collapse onto raft; white cottony mycelium at crown; black sclerotia (resting bodies, like rat droppings) in rotted tissue. Plant collapses suddenly — “lettuce drop”.

Favoured: 15–22 °C, prolonged leaf/crown wetness, poor airflow. Sclerotia survive years in debris.

Cultural: Strip + incinerate any wilted plant within 1 hour of detection. Never compost. Sterilise raft surfaces between cycles (3 % hydrogen peroxide). Reduce tunnel humidity overnight.

3.2.12 Botrytis / Grey Mould (Botrytis cinerea)

Look: Soft brown lesions on senescing/damaged tissue, covered in fuzzy grey-brown sporulation. Typically starts on bruised leaves or stems.

Favoured: 15–22 °C, RH >90 %, leaf wetness, dense canopy.

Cultural: Strip senescing/damaged leaves at thinning. Reduce overnight humidity. Wider spacing. Never harvest into wet leaves.

3.2.13 Bacterial Leaf Spot (Xanthomonas campestris pv. vitians)

Look: Small (2–5 mm) angular water-soaked spots on leaves, turning dark brown/black with yellow halo. Spots limited by leaf veins (giving angular shape — diagnostic).

Favoured: 24–28 °C, wet leaves, splash from overhead water. Late summer thunderstorms.

Cultural: Source clean seed (heat-treated). No overhead irrigation. Sanitise tools between blocks. Strip + incinerate infected plants. Future-fish caution: copper is highly toxic to fish — must replace with biological-only programme before fish go in.

3.2.14 Pythium / Root Rot (Pythium aphanidermatum, P. dissotocum) — DWC-specific killer

Look: Roots brown/grey, sloughing outer cortex (the “skin” slips off, leaving a thin white core); plant wilts mid-day despite full nutrient solution; growth stalls. In severe cases, an entire raft collapses in 48 hours.

Favoured: Nutrient solution >22 °C, low DO (<6 mg/L), organic debris in tank, high EC stress. Summer is highest risk.

Cultural — most important section in this whole document:

• Keep nutrient solution below 22 °C — chiller in summer is non-negotiable
• Maintain DO ≥6 mg/L — oversize air pumps + run 24/7. Test weekly
• Sterilise tank between cycles — drain, scrub, 3 % hydrogen peroxide soak, rinse
• UV steriliser on the recirculation loop — kills zoospores before they spread
• Filter solids — root debris is Pythium food
• Never top up with raw river/borehole water — UV-treat or chlorinate-then-dechlorinate first

3.3 Master Preventive Spray Calendar (4-Week Rotation)

This is the spray plan during normal grow-out (transplant week 1 through week 4 of the head-formation cycle). No sprays in the 7 days before harvest. All sprays applied early evening (16:00–19:00) unless stated. All foliar — both upper and lower leaf surfaces — until run-off.

Then return to Week 1. This rotation cycles 4 different insect MoAs and 4 different fungal MoAs every month — strong resistance-management posture.

Hard timing rules:

• Spray early evening (16:00–19:00) — never with sun on leaves
• Tunnel temp at spray time: ideally 18–25 °C. Never spray sulphur above 28 °C
• No spray within 7 days of harvest. None
• If RH >95 % forecast for next 24 h, postpone biological sprays — they need leaves to dry briefly

3.4 Reactive Triggers + Decision Tree

Action thresholds (when prevention has failed and reaction is required)

Decision tree (run for every observation)

1. OBSERVE — did the daily walk find something? (§3.9)
2. IDENTIFY — what is it? (use §3.2 visual cues; if unsure, photograph + escalate)
3. THRESHOLD — is it above the trigger in the table above?
       ├── NO  → log observation, increase scouting frequency, continue calendar
       └── YES → continue
4. CHOOSE TIER:
       ├── First response: organic reactive product (§3.2)
       └── If organic fails after 2 applications: escalate to chemical reactive
5. FUTURE-FISH CHECK — flag if product unsafe for aquaponic conversion
       (copper, abamectin, imidacloprid, mancozeb — all problematic; document swap-out)
6. PHI CHECK — count days to nearest harvest. Is PHI ≤ days remaining?
       ├── NO  → cannot use this product on this block. Pick alternative or harvest first
       └── YES → continue
7. NOTIFY MANAGER — sign-off required before any reactive spray
8. APPLY — per §3.6 protocol
9. LOG — §3.7 spray log, mandatory
10. RE-EVALUATE at the product's re-spray interval — has the threshold dropped?

3.5 Resistance Management Protocol

Every time we spray a population, the few individuals tolerant to that MoA survive + breed. After 3–4 generations of repeated same-MoA exposure, the population becomes resistant — and the product stops working. Resistance is permanent at the field level. Once you lose a chemistry, you don’t get it back.

The rule: never use the same MoA group two cycles consecutively. Rotate at least every 14 days.

Insecticide MoA grouping (IRAC)

Fungicide MoA grouping (FRAC)

Rotation rule made simple: pick one row from the insecticide table this week; pick a different row next week. Same for fungicides. Multi-site (M-codes) and biologicals (BM02) can be used more frequently — they hit many targets at once.

3.6 Spray Application Protocol + Safety

Operator PPE — non-negotiable for every spray:

• Nitrile gloves (chemical-resistant)
• Eye protection (sealed goggles, not safety glasses)
• Half-face respirator with A1P2 cartridge (organic vapour + particulate)
• Long-sleeve overalls + closed boots
• For copper, sulphur, synthetic chemistry: full Tyvek suit

Tank mixing order — always in this sequence:

1. Water — fill tank to 80 % of final volume
2. Wettable powders / granules (Kumulus DF, DiPel) — dissolve fully with agitation
3. Suspension concentrates (Floramite, Revus)
4. Soluble concentrates (Bioneem, Movento)
5. Adjuvants / wetters (Break-Thru, Agral 90 — last)
6. Top up to final volume with continuous agitation

Coverage requirement: leaf wetness on both upper and lower surfaces, sprayed to point of run-off (the moment droplets just start to coalesce and drip). Lettuce hearts hide pests — angle nozzle to penetrate. Use 0.4–0.6 mm hollow-cone on knapsack; flat-fan on tunnel boom.

Equipment cleaning between products: triple-rinse tank, lines, nozzles. For sulphur, copper or oils: add 100 g/100 L washing soda (sodium carbonate), agitate 5 min, drain, rinse twice more. Dedicated tank for copper if possible.

Mix-only-what-you-need: calculate area × volume × dose. Round up by 10 % for safety. Do not mix excess — biological products lose efficacy within 2 hours of mixing.

Disposal of leftover spray: spray remaining mix onto un-sprayed tunnel ground (never onto crop, never down drain, never into nutrient tank). Triple-rinse equipment, apply rinse water to same ground.

REI (Re-Entry Interval):

• Biologicals (Eco-Bb, Serenade, DiPel, Bioneem): 4 hours (until leaves dry)
• Sulphur, copper, potassium bicarbonate: 12 hours
• Synthetic chemistry (Confidor, Tracer, Movento, Switch, Aliette, Topas, etc.): 24 hours minimum, longer per label
• Post-REI re-entrants still wear gloves until next irrigation cycle

PHI (Pre-Harvest Interval) — critical: see PHI column in every §3.2 table. Never harvest within PHI. Food-safety legal requirement, not a guideline. Block off harvest in calendar after every spray.

3.7 Records the Customer Must Keep

Every record below lives in a single ring-binder on the tunnel office wall + a Google Sheet backup.

(a) Daily IPM walk + scoring sheet: Date • Operator • Block • Pest/disease score (0–3) per category • Notes • Action taken • Signature

(b) Sticky-trap count log (weekly): Week • Trap location • Yellow count (whitefly/aphid/leafminer/fungus gnat) • Blue count (thrips) • Trend vs last week • Replaced Y/N

(c) Spray application log — MANDATORY: Date • Time • Block • Product • Batch number • Active ingredient • MoA code • Dose • Total volume mixed • Volume applied • Operator • Wind/temp/RH • PPE worn • PHI ends • REI ends • Signature

(d) Resistance-management tracker: Week • Insecticide MoA used • Fungicide MoA used • Cumulative weeks on this MoA • Next required rotation

(e) Quarantine register: Date • Block • Issue identified • Plants stripped (count) • Disposal method (incineration/sealed bag) • Spread to neighbour blocks Y/N • Resolved date

3.8 Hard Rules — The Never-Do List

1. Never spray with sun on the leaves — burns leaves, evaporates product, kills biologicals. Early evening only
2. Never combine neem and sulphur in the same tank — phytotoxicity guaranteed
3. Never spray sulphur above 28 °C — leaf burn certain
4. Never harvest within PHI. Check the PHI column. No exceptions for orders or pricing
5. Never reuse spray-tank water the next day — biologicals dead, chemistry degraded, bacterial growth contaminates next batch
6. Never use the same insecticide MoA two weeks running — resistance is permanent
7. Never broadcast metaldehyde slug pellets across the crop — perimeter only, prefer iron phosphate
8. Never compost diseased plant material — incinerate or seal-bag for landfill. Sclerotia survive composting
9. Never top up DWC nutrient tank with untreated raw water — UV or chlorinate-then-dechlorinate first. Pythium zoospores ride in on water
10. Never spray without a written entry in the spray log first — if it’s not logged, it didn’t happen, audit traceability is gone

3.9 Daily 5-Minute IPM Walk-Through

Run this every morning at 07:00. Tick each box. Initial + date.

Nursery (3 points, 90 seconds):

1. Seedling tray surfaces — any fungus gnat adults? any green algae crust? (algae = overwatering)
2. Seedlings — any damping-off (collapsed seedlings at substrate level)?
3. Yellow sticky traps in nursery — count adults, log if >20

Grow-out tunnel (7 points, 3.5 minutes):

4. Walk one full row — random 10-plant inspection: lift outer leaves, check undersides for aphids, mites, downy mildew sporulation
5. Sticky traps (1 yellow + 1 blue per 50 m²) — quick count, flag if above threshold (§3.4 table)
6. Any wilting plants mid-canopy? — flag immediately for Sclerotinia / Pythium check
7. Raft surfaces — any slime trails (slugs) or frass (caterpillars)?
8. Lift 3 random rafts — root colour: white-cream = healthy, brown/grey = Pythium alarm
9. Tunnel climate readout — log temp, RH, nutrient solution temp, DO. Any out of range?
10. Vents and insect mesh — intact, closed where required, no gaps?

Action: Anything flagged → log it, photograph it, escalate to manager within the hour. The walk is useless if findings don’t trigger action.

Closing

This document is the operational backbone for your fancy lettuce DWC line. Every number is sized to your facility — 6 tunnels, 12 sections, 96 boards per section, 16 holes per board, 8-6-2 mix, 5 cultivars per week, 6-week rotation, ramp 40 % → 100 % over five months. Every spray product is SA-available. Every dose, every PHI, every REI is locked.

Print the calendars. Laminate the daily walk-through. Sign the spray log every time. Run the rhythm, sell the output, and the system runs you.

We refine these numbers in the first 90 days from real readings — your real water chemistry, your real tunnel microclimate, your first buyer commitments. The skeleton above is what we plant against from Day 1.

— Richard Buschagne, YBA Group