# Crop-Chem API Lessons

Curated agronomy + label-handling knowledge that an LLM should know
*before* giving recommendations from the labels corpus. Surfaced by
the `crop_chem_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.

---

## Topic: how-to-use-this-corpus

The crop-chem-docs label 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.