Brown bacterial blotch in button mushrooms
Look for: Tan to brown cap lesions, sometimes becoming darker or sunken.
Do not confuse with: Bruising after handling, fungal lesions and chemical injury.
Read checks and response →Mushroom disease library · Field companion
Disease picture reference
Real research photographs with attribution, host context and lookalike warnings. Generated teaching scenes are never presented as pathogen evidence.
Real symptoms, with the original context
Compare structure, location and progression—not just colour. These images are from published research, not our farm cases. Some are experimentally induced symptoms. Captions identify that distinction. Tap a source to inspect its full figure and methods.
Brown blotch in oyster mushrooms
Look for: Pale brown patches becoming darker or depressed.
Do not confuse with: Dry edges, bruising, age-related yellowing and other bacterial rots.
Read checks and response →Morel red-stipe / bacterial-disease investigation
Look for: Abnormal red-stipe appearance in the reported syndrome.
Do not confuse with: Abiotic injury, ageing and fungal or secondary decay.
Read checks and response →Oyster mushroom viruses
Look for: Slower mycelial growth or abnormal fruiting in documented infected strains.
Do not confuse with: Old or damaged spawn, substrate failure and environmental stress.
Read checks and response →Dry bubble
Look for: Undifferentiated dry masses when young tissue is affected.
Do not confuse with: Wet bubble, which can also distort developing mushrooms.
Read checks and response →Wet bubble
Look for: Irregular fleshy growth with white surface growth early in development.
Do not confuse with: Dry bubble; early distorted tissue is not reliably separated by a casual photograph.
Read checks and response →Cobweb disease
Look for: Expanding wispy or cottony patches crossing casing and mushroom surfaces.
Do not confuse with: Normal crop mycelium, Mucor-like growth and Syzygites.
Read checks and response →Green mould in button compost
Look for: White growth followed by green sporulation in compost or casing.
Do not confuse with: Penicillium, Aspergillus and other green-sporing contaminants.
Read checks and response →Shiitake block green mould
Look for: Distinct green growth, sometimes preceded by a soft white patch.
Do not confuse with: Normal block browning and maturation.
Read checks and response →Wood-ear brown rot
Look for: Abnormal browning accompanied by deterioration.
Do not confuse with: Normal brown pigmentation.
Read checks and response →Morel white mould and fungal rot
Look for: White surface growth on affected fruit bodies.
Do not confuse with: Water injury, secondary saprophytes and bacterial decay.
Read checks and response →What a photograph cannot tell you
- A green colony cannot distinguish all Trichoderma species from other green moulds.
- A distorted mushroom cannot confirm a virus. Normal strain form and environmental conditions must be checked.
- A normal-looking crop cannot rule out foodborne contamination.
- Small organisms need identification: a mite or nematode may be harmful, neutral or beneficial.
Where a verified reusable image is unavailable, the condition page says so and links the research. We have not filled those gaps with synthetic pathogen photographs.
Illustrated field skills
Learn where to look—and what to record
These eight teaching plates explain anatomy, crop systems and observations. They are deliberately separate from the real research photographs above. Numbered details have readable explanations below each picture.
Read the bag before opening it
- Closure and entry points
Record whether the first change is near a seal, filter, tear or fruiting cut. Do not open the bag to investigate.
- Patch boundary
Photograph its position and change over time. A green patch does not identify a genus or species; early growth may be white.
- Batch identity
Keep spawn lot, substrate treatment, inoculation date and rack position together. Compare other bags from the same batch.
Name the part that changed
- Cap surface
Record a local spot versus whole-cap colour, and whether it was present before picking.
- Gills underneath
Separate normal maturity-related pigmentation from unusual wetness, exudate or deterioration.
- Inside the stem
Internal changes can differ from the outside. Obtain sampling instructions before cutting suspect material.
- Casing and compost
Note whether the change starts in the fruit body, the casing surface or the substrate below.
Wet surfaces and dry edges tell different stories
- Surface water
Record watering time, condensation and how long caps remain wet. Room relative humidity alone does not describe cap wetness.
- Drying and cracking
Check where damage occurs and when it appeared. Compare airflow, water supply and maturity with a same-strain crop.
Small organisms are not all the same
- An adult fly
Record where it is seen and whether it walks, runs or flies. Adult identification and larval damage are separate observations.
- A larval stage
A gnat-like legless larva is shown. Do not assume that every pale organism in substrate is the same pest.
- A mite
Mites may feed on crop tissue, mould or other organisms. Presence alone is not proof of crop damage.
- A nematode-like form
Nematode groups have different roles. Microscopic examination and specialist identification may be necessary.
Compare the air, the substrate and the surface
- Room air
Use time-stamped readings at representative positions. One sensor can miss a rack-level or doorway difference.
- Substrate
Record substrate temperature separately from room air using the farm’s appropriate hygienic measurement procedure.
- Cold or wet surfaces
Map condensation, leaks and wet crop zones. Compare the pattern with watering and temperature changes.
Find the problem in the correct growing system
- Casing layer
For crops that use casing, trace storage, handling and the casing lot separately from the compost.
- Compost below
Compare the compost lot and preparation history. White growth is not, by itself, proof of either purity or contamination.
- Straw bag
Record treatment, cooling, spawning and the first affected position through the intact bag.
- Wood-substrate block
Check the filter, seal and batch history without opening suspect material. Normal block appearance depends on crop and stage.
Follow the culture from source to evidence
- Trace the culture
Keep the supplier, species, strain, spawn lot, receipt date and storage history.
- Compare like with like
Compare the same strain and stage under recorded conditions. Natural strain variation can resemble a disorder.
- Ask before sampling
Contact a qualified laboratory about the diagnostic question, accepted material and shipping instructions.
Look at the handling history as well as the crop
- Bruising or colour change
Ask whether it appeared before picking, during handling or in storage. A brown area is not automatically bacterial blotch.
- Moisture inside a pack
Record condensation, temperature changes and elapsed time. Do not use a visual match to release a suspect lot.
- Time, temperature and lot
Link harvest, packing and transport records so affected produce can be traced and assessed.
Teaching illustrations have a different job
Eight numbered observation plates and three workflow scenes explain anatomy, growing systems, moisture, pests, culture history, harvest handling, recording and separation of work areas. They do not establish a pathogen, identify every organism or prove that a building meets biosecurity requirements. A generated grower is not a real scientist or an institutional endorsement.
Learn to document your own crop →