the soil is lightly turned over, you may well see the grey caterpillars of
the Swift Moth in the soil feeding on the roots.
Prevention is the only practical action. First, don't plant beetroot in
the same soil two years running. Second, make sure the area is weed free -
the caterpillars feed on the roots of some weeds, especially docks, and
these only encourage them.
an attack does strike, destroy the affected plants by burning them. Dig
the soil surface to expose the caterpillars to birds.