Organism
Venturia inaequalis
The cause of apple scab, the most widespread apple disease in temperate regions, and one whose consequences for cider fruit are far smaller than for dessert fruit.
Also called apple scab.
- Kind
- Mould
- Binomial
- Venturia inaequalis
- Role
- Present throughout
What it does
- Overwinters in fallen leaves, where it forms perithecia that discharge ascospores in spring — the primary infection that starts each season, and the stage that leaf-litter management targets.
- Infects leaves and fruit during periods of leaf wetness, with infection risk predicted from combinations of wetness duration and temperature.
- Produces olive-brown lesions that become corky and cracked on fruit, and defoliates trees in severe seasons, reducing photosynthesis and the following year’s cropping.
- Cracks fruit skin where infection is severe, creating the wounds through which rot fungi such as Penicillium expansum and Monilinia enter.
Conditions it works in
What the organism tolerates and what suppresses it. These are the levers a maker actually has: temperature, acidity, air, alcohol and sulphite.
| Condition | What is recorded |
|---|---|
| Temperature | Infects across roughly 5 °C to 25 °C, with the wetness duration required falling as temperature rises. |
| Oxygen | Aerobic; a leaf and fruit surface organism with no fermentation role. |
Faults it causes
Faults this organism is implicated in. Several are faults only against a particular expectation — the same activity is a signature elsewhere.
Where in the process it appears
Pest and disease management
Keeping scab, canker, rots and the main insect pests to a level the orchard can carry, at a cosmetic standard well below dessert fruit but without allowing rot into the crop.
Orchard floor management
What is grown, mown, grazed or suppressed beneath and between the trees, which affects tree vigour, juice nitrogen, harvest logistics and the biological interest of the ground.
Pruning
The recurring cut made on a cropping tree to keep light in the canopy, renew fruiting wood, hold the balance between growth and fruit, and take out disease and deadwood.
Fruit sorting
Taking rotten, mouldy and damaged fruit and foreign material out of the crop before it reaches the mill, which is the primary control on patulin in cider.
Ripeness assessment
Judging when cider fruit has converted enough starch, loosened enough on the spur and hardened enough for the store to be worth gathering.
Orchard nutrition
Deciding what the trees are fed and how much, a balance in which too little nitrogen shows up as a difficult fermentation and too much shows up as canker and soft growth.
About Venturia inaequalis
Apple scab is the disease that dominates spray programmes in commercial apple growing, and its status in cider is genuinely different. A scabbed apple is unsaleable as dessert fruit because scab is a cosmetic defect on something sold by appearance. A scabbed apple pressed for cider is, for the most part, juice — the lesions are superficial, and lightly scabbed fruit makes cider that is not measurably different.
That is not a licence to ignore it. Severe scab defoliates trees, which reduces sugar accumulation in the fruit and the following season’s crop, and severe fruit infection cracks the skin, opening the wounds that rot fungi need. The threshold at which scab matters for cider fruit is simply much higher than for dessert fruit, and cider orchards are correspondingly managed with lower input in many traditional systems.
The control that follows from the biology is leaf litter. The fungus overwinters on fallen leaves and starts each season by discharging ascospores from them, so anything that removes or accelerates the breakdown of leaf litter — mowing, mulching, urea application, grazing — reduces the primary inoculum. As with `neonectria-ditissima`, this organism has no fermentation role and is filed as `ubiquitous` for want of a category in the schema that fits an orchard pathogen.
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- How should a cider tree be pruned
- When are cider apples harvested — In the northern hemisphere the cider harvest runs from about September to November, with late bittersweets such as Dabinett and Vilberie coming in last. Cider fruit is generally picked riper than dessert fruit, and often gathered from the ground.
- Do you need to sort apples before pressing
- What is mould taint in cider
Where to go next
- All organisms — Grouped by what each does in the ferment, and by what kind of organism it is.
- Compounds — The chemistry this microbiology produces.
- Troubleshooting — Work from the symptom in the glass back to the organism.
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
NIAB (incorporating East Malling Research)
NIAB · research institute · retrieved 2026-08-24
East Malling developed the M-series apple rootstocks that determine tree size in essentially every modern orchard, cider orchards included. The authority CiderHQ uses for rootstock behaviour.