Kohlrabi diseases and pests
The database lists 4 problems recorded on this crop. 1 of them can cost the whole harvest, and 1 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
Rotate this bed and everything else in the same family on at least a three-year cycle. 1 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: Clubroot
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: Clubroot
Keep watering and feeding even rather than generous. Several problems on this list are not infections at all: they are the plant reacting to a swing in water, temperature or nutrient supply, and consistency prevents them where no spray can.
Applies to: Fruit Cracking
Keep affected material out of the compost heap — 1 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: Clubroot
Every listed problem
Ordered by how much they can cost you.
Fungal diseases(1)
- ClubrootSevere
Stunting, wilting in midday heat, and yellowing of older leaves above ground; swollen, distorted club-shaped roots below ground that rot and smell.
- How it spreads
- Soil and crop debris
- Compost
- Keep out of the compost
- Conditions
- 12–27°C · humidity ≥70% · wet leaves / rain
- First move
- Fix the cause, not the leaf
Also at risk: Cabbage, Radishes, Kale, Broccoli, Cauliflower, Brussels sprouts
Pests(2)
- CaterpillarsModerate
Ragged holes and chewed leaf margins, stripped stems, dark green or black droppings (frass), and tunnelled or bored fruit; large green or striped larvae present.
- How it spreads
- Carried by insects
- Compost
- Safe to compost
- Conditions
- 15–33°C
- First move
- Treat, then re-check in 5–7 days
Also at risk: Cabbage, Kale, Broccoli, Cauliflower, Brussels sprouts, Sweetcorn
- Flea BeetlesModerate
Dozens of small round holes peppering the leaves, heaviest on the youngest growth. Seedlings can be killed outright or checked so badly they never catch up. The beetles scatter with an audible flick when you lean over the row.
- How it spreads
- Carried by insects
- Compost
- Safe to compost
- Conditions
- 18–32°C · dry air ≤55%
- First move
- Treat, then re-check in 5–7 days
Physiological disorders(1)
- Fruit CrackingMild
Concentric or radial splits in the skin around the stem or across the fruit, which then invite rot and insects; most common after rain on ripening fruit.
- How it spreads
- Not contagious
- Compost
- Safe to compost
- Conditions
- wet leaves / rain
- First move
- Fix the cause, not the leaf
Why rotation matters here
1 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.