crop-chem-docs/docs_mcp/lessons.md

PPLS API Lessons

Curated agronomy + label-handling knowledge that an LLM should know before giving recommendations from the labels corpus. Surfaced by the ppls_api_lessons MCP tool.

Each top-level ## Topic: <slug> block is independently retrievable. The tool docstring tells the LLM to call this proactively before answering any pesticide recommendation question.

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Topic: how-to-use-this-corpus

The PPLS docs corpus is the source of truth for what's on the label. You should:

1. Run search_docs first with the user's natural-language question. Hybrid+rerank mode (default in production) returns the most relevant label chunks across Bayer + every major US ag-chem registrant via EPA PPLS.
2. Cite the EPA Reg No next to any product recommendation. Format: PRODUCT NAME (EPA Reg X-Y). Drop this and the recommendation is ungrounded.
3. Link the label PDF URL so the user can verify and the spray operator can have the actual label on hand. The sidecar's label.url is in the search result metadata.
4. Quote — don't paraphrase — rate ranges. Labels say "16 to 32 fl oz/A"; do not tighten that to "use 24 fl oz/A" unless the label gives a specific use case at that rate.
5. If you can't find a label-grounded answer, say so. Better to return "no label in corpus matches this; consult the manufacturer or your CCA" than to hallucinate a rate.

The corpus is scoped to US row crops: corn, soybeans, wheat. Outside that scope, results are sparse or empty.

Topic: epa-signal-words

Every EPA-registered pesticide label has a signal word in the upper front panel. It maps to acute toxicity:

Signal word	Toxicity	Typical examples
DANGER + "POISON" + skull-and-crossbones	Cat I, highly toxic	Paraquat (Gramoxone), some methyl bromide
DANGER (no POISON)	Cat I (skin/eye irritation only)	Some restricted-use ester formulations
WARNING	Cat II	Many fomesafen formulations, some 2,4-D esters
CAUTION	Cat III/IV, least toxic	Most modern soybean/corn herbicides — glyphosate, mesotrione, fomesafen amine salts
(none)	Cat IV	A few biopesticides + some adjuvants

When recommending a DANGER-labeled product, always call out PPE requirements (typically chemical-resistant gloves, footwear, eyewear, respirator depending on activity).

Topic: rei-phi-fundamentals

Two distinct intervals — don't confuse them:

• REI (Restricted Entry Interval): minimum time AFTER application before a worker may enter the treated area without the label's full PPE. Typical values: 4, 12, 24, 48 hours.
• PHI (Pre-Harvest Interval): minimum time BETWEEN last application and crop harvest. Typical values: 7, 14, 21, 30, 60, 90 days depending on chemistry + crop.

Always state both when relevant to the workflow. For burndown applications, PHI rarely matters; for in-crop foliar, it's critical.

Topic: rup-handling

Restricted Use Pesticide (RUP) is a federal designation that means: the product can only be purchased, possessed, and applied by (or under direct supervision of) a certified pesticide applicator.

Row-crop products you'll commonly see in RUP class:

• Paraquat-based (Gramoxone Inteon, Helmquat, Firestorm) — RUP + special closed-system training required since 2019
• Dicamba formulations approved for in-crop soybean/cotton (XtendiMax, Engenia, Tavium) — RUP + applicator training every year
• Some pyrethroids (Warrior II, Mustang Maxx) — RUP in some states

When recommending an RUP, always say:

"This is a Restricted Use Pesticide — application requires a certified applicator and proper recordkeeping per state regs."

Never give a "casual" application recommendation for an RUP. The recommendation must include the applicator-certification framing.

Topic: supplemental-labels-24c-2ee

Beyond the main federal (§3) label, products often have:

• 2(ee) recommendations: manufacturer-issued, label-compliant additional uses that don't require formal re-registration. These add new tank-mixes, crops, or pests within the existing label's authority. You can recommend a 2(ee) — but tell the user the 2(ee) document itself must be in their possession at spray time.
• 24(c) Special Local Need (SLN): state-specific labels approved by the state lead agency for a problem peculiar to that state. Same possession-at-spray rule. SLNs are common for cotton in TX and rice in southern states; less common in OH row crops.

The Bayer scraper captures these as supplemental_documents in each label's sidecar (kind: "2EE" or "24C"). For EPA PPLS labels, the main label is what's in the corpus.

Topic: tank-mix-fundamentals

When recommending tank mixes:

1. The more restrictive label wins. If product A allows 2 qt/A max in-crop and product B caps tank-mix partners at 1 qt/A for that crop, the cap is 1 qt/A.
2. Antagonism is real. A few well-known antagonisms:
   • Glufosinate + grass herbicides (clethodim, sethoxydim) → reduced grass control. Apply grass herbicides separately, 7 days apart.
   • Atrazine + dicamba + Group 15 (e.g., S-metolachlor) all-at-once can hammer corn under cold/wet conditions.
   • 2,4-D ester + glufosinate → can reduce glufosinate activity.
3. Adjuvant compatibility:
   • Glufosinate (Liberty) REQUIRES AMS @ 1.5-3 lb/A. No exceptions.
   • Glyphosate works best with NIS in soft water, or with AMS conditioner in hard water (Mg/Ca > 200 ppm).
   • PPO herbicides (lactofen, fomesafen) often want COC, not NIS.
4. Always check both labels' "Tank-Mix Compatibility" or "Restrictions" sections before recommending — the corpus has these sections; pull them with search_docs.

Topic: resistance-management-hrac-frac-irac

Herbicide resistance is the single biggest threat to row-crop weed control in the US Midwest. Always communicate resistance group when recommending:

• HRAC (Herbicide Resistance Action Committee) groups (formerly WSSA numbers). Use the number not just the name — farmers recognize "Group 14" faster than "PPO inhibitor".
• FRAC for fungicides.
• IRAC for insecticides.

Key Midwest resistance hotspots:

• Waterhemp + Palmer amaranth: resistant to Groups 2, 5, 9, 14, 15, 27 in places. Means glyphosate, ALS, atrazine, fomesafen, metolachlor, and HPPDs (mesotrione) all have spotty efficacy. → Always mix MOAs; never spray a single Group twice in a season.
• Marestail/horseweed: glyphosate-resistant nationwide; 2,4-D remains the burndown anchor + Sharpen (saflufenacil, Group 14).
• Giant ragweed: glyphosate + ALS resistant in many areas.

When the user asks for a recommendation, say the group number (e.g., "Sencor (metribuzin, Group 5)") so they can rotate.

Topic: glufosinate-application-rules

Glufosinate (Liberty 280 SL, Cheetah Max generic, etc.) is unique:

• Photosynthesis-dependent: needs bright sun within ~4 hours of application. Cloudy days = poor control.
• Needs warmth: ideally daytime temp > 60°F at application.
• AMS is mandatory at 1.5-3 lb/A.
• Coverage trumps droplet size: use flat-fan or AIXR nozzles, 15-20 GPA carrier, medium droplets. Don't go ultra-coarse to reduce drift.
• Two-pass strategy for heavy weed pressure (V2 + V4-V5 in soybean) outperforms a single higher-rate pass.
• Weed-size critical: best on weeds ≤ 4". After 6" efficacy drops.

Topic: dicamba-application-rules

Dicamba in-crop in soybean/cotton (XtendiMax, Engenia, Tavium) is under intense EPA scrutiny. Current label rules (verify against the specific label in corpus before recommending):

• RUP + annual applicator training required.
• State and date cutoffs: most states have application date cutoffs (e.g., June 30 in OH for soybean; varies by state). Check the state-specific 24(c) label.
• Wind: 3-10 mph at boom height. No spraying during temperature inversions (typically pre-sunrise + late evening).
• Buffers: downwind buffer to sensitive areas (typically 110-220 ft; depends on state + downwind sensitivity).
• Approved nozzles only: TTI or AIXR with very-coarse-to-ultra- coarse droplets. Manufacturer publishes approved nozzle lists.
• Tank cleanout: triple-rinse with ammonia-based cleaner after every load. Dicamba contamination of subsequent loads is the #1 off-target damage cause.

If the label in the corpus is older than the current EPA decision, say so and direct the user to the latest manufacturer label — EPA has revised dicamba registrations multiple times.

Topic: lake-erie-watershed-ohio

Ohio's H2Ohio program + the Western Lake Erie Basin (WLEB) impose additional considerations for nutrient/pesticide runoff:

• Atrazine: WLEB subwatersheds have voluntary reduction targets; formal label restrictions in some HUC-12 watersheds. Atrazine over 0.75 lb/A on highly-erodible land may require soil conservation practices (cover crops, buffer strips).
• Dicamba: see Topic: dicamba-application-rules. OH cutoff has historically been June 30 for in-crop soybean.
• 2,4-D + 2,4-DB: drift sensitivity in OH given the high mix of row-crop, specialty-crop (tomato, grape), and homeowner areas.

When recommending to OH farmers, surface H2Ohio cost-share options if relevant (no-till + cover crops + variable-rate nutrient management can offset chemistry needs).

Topic: scn-and-other-seed-treatment-context

Soybean cyst nematode (SCN) is universal in OH/IN/IL/IA. When recommending a soybean program, always check whether the seed treatment includes nematicide/SCN protection:

• Abamectin (Avicta) — original SCN nematicide seed treatment
• Fluopyram (ILeVO) — broader nematode + SDS suppression
• Pydiflumetofen (Saltro) — newer; nematode + SDS protection without ILeVO's halo effect on seedling
• Pasteuria nishizawae (Clariva) — biological nematicide

This isn't strictly a "pesticide label" topic but it's the right context for ANY soybean herbicide recommendation: a great herbicide program on SCN-infested fields without nematicide seed treatment is leaving yield on the floor.

Topic: drift-management-essentials

Drift mitigation is increasingly enforced and increasingly important for off-target damage liability:

• Wind: most labels specify 3-10 mph at boom height. Below 3 mph risks temperature inversion (worst case: cool morning over warm ground, fine spray hangs and drifts miles).
• Temperature inversion detection: smoke test. Smoke that rises and dissipates = no inversion. Smoke that hangs flat = inversion.
• Nozzle selection: AIXR / TTI / TT — air-induction nozzles produce larger droplets that drift less. Required for dicamba/2,4-D.
• Boom height: lower is better for drift. 20 inches over canopy for AIXR; manufacturer specs for TTI.
• Buffer to sensitive crops: tomatoes (esp. for 2,4-D + dicamba), grapes, organic fields, residential lawns. Always check downwind.
• Adjuvant choice affects drift: NIS reduces droplet size; deposition aids (e.g., InterLock, Strike Zone) increase droplet weight and reduce drift.

Topic: how-to-format-recommendations

When the LLM produces a pesticide recommendation, the canonical shape that makes it actionable for a farmer:

**[Product name]** (EPA Reg [X-Y]) — [active ingredient(s)], [Group N]
- **Rate:** [from label, with range]
- **Timing:** [growth stage / DAT]
- **Carrier + adjuvant:** [GPA + adjuvant requirements]
- **REI/PHI:** [from label]
- **Label PDF:** [URL from search result]
- **Notes:** [resistance group, drift considerations, RUP framing if
  applicable, tank-mix antagonism warnings]

Skip the canonical shape and the recommendation is hard to apply without the farmer doing their own label hunting. The corpus has everything needed — surface it cleanly.