We are having trouble with root maggots damaging our rutabagas. We planted hairy vetch as a companion crop to attract ladybugs. We had some beautiful rutabagas but lost many, as consumers demand near perfection. We grow two acres of rutabagas, would it be cost effective to introduce more beneficials (Ladybugs?) on a field this large. How about Bt organic spray, is it effective on root maggots?, and does it harm beneficial predators?
We are harvesting smaller gourmet rutabagas and it would be financially viable if we could solve this problem.
Thanks for your organic efforts,
Bruce Miller, Pemberton, BC, Canada
First, you need to understand the lifecycle of the root maggot.
Root maggots overwinter - lay dormant in the soil as larvae. In spring, larvae move near the top soil where they pupate. In late spring, the female adult flies lay their eggs in the soil near the base of the plants. Larvae hatch and feed on the roots.
The companion plant, hairy vetch that you planted to attract ladybirds/ladybugs, unfortunately is not helping because ladybirds only feed on the top of the plant, leaving the roots unaffected.
1. Introduce rove beetles which prey on root maggots. Click here for a picture of the rove beetle. If the root maggot problem continues, clear the area of dead, decaying or organic compost matter.
2. As soon as seeds are sown, cover them with a fine mesh cover - could be expensive.
3. A square of tar paper or similar placed at the base of each transplant prevents adult cabbage maggots from laying eggs around the stems - could be labour intensive.