Observation & Pattern
Most crop losses are named wrongly on the first day, and the wrong name leads to the wrong action. Describing what you see before deciding what it is costs nothing.
- By the end you can describe a problem in five facts: what, where, how many, since when, what changed.
- By the end you can tell a spreading pattern from a uniform or localised one.
- By the end you can separate a mushroom sign from a room sign and count flies against a published threshold.
From symptom to cause
A first look, not a diagnosis. Source: ICAR-DMR manual and disease bulletin.
| What you see | Likely cause | First step |
|---|---|---|
| Long stems, small caps | CO₂ too high (above about 1,500 ppm) | More fresh air |
| Green patches on compost | Trichoderma; low pH or leftover ammonia | Isolate, remove; check next batch |
| No pins after casing | Room not aired and cooled | 16 to 18 °C, ventilate |
| Brown sunken spots on caps | Bacterial blotch; wet caps | Dry the surface, humidity under 85% |
| White wet lumps | Wet bubble from casing | Salt, remove; steam next casing |
| Small flies | Sciarid or phorid flies | Screens, light traps, hygiene |
Read numerical examples with their source, method and crop context. They are not universal operating instructions. Historical prices are not current quotations.
Look, explain, then apply
Document the room, affected area and detail. All pictured scenes are synthetic; these are not disease-reference photographs or laboratory findings.
See where this fits in the full workflow →01Describe first, name later
A disease name is a conclusion. An observation is a fact. When a grower says "I have green mould", the adviser still asks: green where, on compost or casing, in one bag or twenty, since when? The name skipped every question that decides the action.
ICAR-DMR describes bacterial blotch by behaviour, not name: cap spots that enlarge when temperature is at least 20 °C and a film of water stays on the cap more than 3 hours. That tells you where to look, what to measure and what changed. Write the description before any name; if the name proves wrong, the description is still true.
02The five facts
Every diary entry carries five facts. What: the sign in plain words, with a photo and a coin for scale. Where: room, rack, shelf height, bag numbers, distance from door and air inlet. How many: a count, not "some", repeated 48 hours later. Since when: the date and the crop day, meaning days after spawning or casing. What changed: watering, a power cut, a new casing lot, a visitor, in the previous three days.
The five facts do half the diagnosis. Trouble only near the inlet points at air. Trouble in every bag from one compost batch points at compost. Trouble the day after a power cut points at temperature.
03Reading the pattern
Pattern is the shape of the problem across the room. Uniform: every bag the same, usually environment or a whole compost or casing lot. Spreading: a few bags on day one, neighbours by day three, the signature of infection or a moving pest. Localised: only under the leak or by the door, so look for a physical cause there. Single bag: one odd bag, often a filling or spawn fault.
Speed matters as much as shape. ICAR-DMR warns that dry bubble, left uncontrolled, can destroy a crop in 2 to 3 weeks. A count that doubles every two days is an emergency; a flat count is a fault, not an epidemic.
04Mushroom sign or room sign?
Some signs that look like disease are the room talking. ICAR-DMR describes high carbon dioxide at pinning producing onion-shaped mushrooms with a bulbous base and small cap, and later long stalks with small open caps. In oyster the same cause gives a trumpet-mouth shape. No organism is involved; spraying wastes money and adds residue.
Pests are counted, not guessed. ICAR-DMR's sciarid table says any live adult in the first flush is already a reason to act, and from the second flush more than 20 per trap per week. NHB describes the trap: a 15 W yellow bulb over a polythene sheet coated with mustard oil.
A ten-minute observation walk, daily this week
- Walk the same route daily: door, inlet side, middle, far wall, bottom and top shelves.
- Write the five facts for anything unusual and photograph it with a coin for scale.
- Count affected bags today and after 48 hours; write both numbers side by side.
- Hang one yellow light trap and record the weekly count beside the flush number.
Write in your farm diary: Date, crop day, room, five facts, count now and at 48 h, trap count, pattern word.
Mistakes that cost a crop
- Naming the disease first and fitting evidence to it, so the room is never checked.
- Writing "some bags" instead of a count, which hides whether the problem is spreading.
- Photographing the mushroom but not its position, so the pattern is lost.
Check yourself
Three questions, instant answersLeggy mushrooms with small open caps appear only far from the inlet. First suspect?
Which entry is an observation, not a conclusion?
Second flush, 8 sciarid adults in the trap this week. Action?
An editorial self-check, not a certificate. Answers are not stored, not even on this device.
Words used in this lesson
- Symptom
- What the crop shows: spot, shape, colour, smell. Not the cause.
- Crop day
- Days counted from spawning or casing.
- Action threshold
- A published count at which to act.
References & further reading
Identification and current India label verification remain separate gates.
Open current reference