Potatoes diseases and pests
The database lists 6 problems recorded on this crop. 4 of them can cost the whole harvest, and 6 survive in soil or debris into next season — those are the ones that decide your rotation. The largest number are active in June.
Pressure through the year
The number of problems listed as active in each month. Pick a month to see what to sow, plant and harvest then.
Start from what you can see
What actually prevents them
Water at the base of the plant in the morning, never over the leaves. Splashing soil onto foliage is the delivery route for every problem listed here, and morning watering lets anything that does land dry before nightfall.
Applies to: Early Blight
Mulch the soil surface. A physical barrier between last season's spores and this season's lowest leaves removes the first infection of the year, which is the one that seeds all the others.
Applies to: Early Blight
Give the plants their full spacing 30×70 cm and keep the centre of each one open. Air moving through the planting dries the leaves faster, and leaf wetness duration is what turns a spore landing into an infection.
Applies to: Late Blight, Potato Common Scab
Rotate this bed and everything else in the same family on at least a three-year cycle. 6 of the problems below survive in soil or crop debris between seasons, so returning the same crop to the same ground hands them the host they were waiting for.
Applies to: Late Blight, Colorado Potato Beetle, Early Blight, Potato Virus Y and 2 more
Clear and remove the spent crop at the end of the season rather than digging it in. Debris left on the surface is where the persistent problems overwinter, and next spring they start from your own bed rather than from somewhere else.
Applies to: Late Blight, Colorado Potato Beetle, Early Blight, Potato Virus Y and 2 more
Control sap-sucking insects early, before the population is obvious. Several of the problems here are carried plant to plant by aphids or thrips, and once a virus has arrived there is no treatment — only the vector was ever treatable.
Applies to: Potato Virus Y
Keep affected material out of the compost heap — 3 of these survive a garden heap and come back with the finished compost. Bag it for municipal green waste, which is composted at temperatures a garden heap does not reach.
Applies to: Late Blight, Early Blight, Potato Virus Y
Every listed problem
Ordered by how much they can cost you.
Fungal diseases(3)
- Late BlightCritical
Dark, water-soaked greasy patches on leaves that rapidly turn brown; white fuzzy sporulation on leaf undersides in humid mornings; firm brown lesions on stems and fruit. Whole plants can collapse within days.
- How it spreads
- Wind-blown spores
- Compost
- Keep out of the compost
- Conditions
- 10–25°C · humidity ≥90% · wet leaves / rain
- First move
- Remove affected material now
Also at risk: Tomatoes
- Early BlightSevere
Brown spots with concentric rings forming a target or bullseye pattern, surrounded by yellow halos, on older lower leaves first. Severe defoliation and dark leathery lesions near the stem end of fruit.
- How it spreads
- Rain and irrigation splash
- Compost
- Keep out of the compost
- Conditions
- 20–32°C · humidity ≥75% · wet leaves / rain
- First move
- Treat, then re-check in 5–7 days
Also at risk: Tomatoes
Raised, corky, brown patches on the tuber skin, sometimes sunken and star-shaped in severe cases. The haulm looks completely healthy — the first sign is at lifting. Beetroot, radish and parsnip growing in the same soil can show the same rough patches.
- How it spreads
- Wind-blown spores
- Compost
- Hot compost only
- Conditions
- 18–30°C · dry air ≤60%
- First move
- Watch it before you act
Viral diseases(1)
- Potato Virus YSevere
Mottled light and dark green leaves, crinkled and often with dark necrotic streaks down the stems and leaf veins. Plants are noticeably shorter than healthy neighbours and drop their lower leaves early. Tubers may show sunken rings.
- How it spreads
- Carried by insects
- Compost
- Keep out of the compost
- Conditions
- Spread by handling, insects or soil — not weather-triggered
- First move
- Remove affected material now
Pests(2)
- Colorado Potato BeetleSevere
Rounded yellow-and-black striped beetles, plump orange-red humpbacked larvae, clusters of orange eggs under leaves, and rapid defoliation that can strip plants bare.
- How it spreads
- Soil and crop debris
- Compost
- Safe to compost
- Conditions
- 18–33°C
- First move
- Remove affected material now
Also at risk: Aubergines
- WirewormsModerate
Narrow, clean holes bored straight into potato tubers, carrots and other roots, often with secondary rot following. Seedlings and young transplants wilt and die from stems chewed at soil level. The larvae are thin, tough, orange-brown and up to 25 mm long.
- How it spreads
- Soil and crop debris
- Compost
- Safe to compost
- Conditions
- 8–25°C
- First move
- Fix the cause, not the leaf
Why rotation matters here
6 of these overwinter in the soil or in crop debris rather than on the plant. Pulling the sick plant does not remove them: they wait for the same host to come back to the same ground.