Cabbage root fly
Cabbage root fly lays eggs at the base of brassicas. The white maggots eat the roots of transplants, which wilt and collapse, and tunnel into radishes, turnips and swedes.
Pests
What it looks like
Wilting in a newly planted brassica row is the warning.
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Wilting transplants Leaves flag and turn bluish in sun. -
Eaten roots Few roots left, with white maggots. -
Tunnelled radishes Brown tunnels through radishes and turnips. -
Stunted plants Survivors grow poorly.
How to confirm it
Pull a wilting plant.
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Look at the roots
Maggots and eaten roots confirm it.
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Timing
Spring transplants are most at risk.
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Check root crops
Tunnels in radishes.
What to do
Stop the eggs being laid.
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Collars
Fit a 10 cm (4 in) collar of felt or card flat around each transplant stem.
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Cover with mesh
Fine mesh from planting keeps flies off.
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Pull and bin
Remove dying plants with their maggots.
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Nematodes
Biological nematodes watered in can reduce larvae.
Prevent it next time
- Rotate brassicas.
- Plant strong transplants that establish fast.
- Cover radishes and turnips.
What not to do
Do not leave infested plants in the ground; the maggots pupate and emerge again.
In the growing guides
Where the guides mention it, with plant-specific advice.
Sources
- Cabbage root fly, Royal Horticultural Society