What is cabbage root fly?
The cabbage root fly, also known as the cabbage fly, (Delia radicum) is a common pest most often found in crops and wildflowers of the cabbage family. The adult individual measures about 6 mm, is grey in colour with black bristles and colourless wings. The elongated eggs are 1.2 mm in size and white in colour. The larvae are white or whitish-yellow, 7-10 mm in size, legless, with a wreath of appendages at the end of the body. The pupa is about 5-6 mm in size, initially yellowish brown turning to brown.
Depending on weather conditions, this pest occurs in 2-4 generations. The cabbage fly lays about 120 eggs on the soil surface close to the host stem, or sometimes on the plant.
The larvae are root feeders, but also feed on aboveground parts of the plant. They create most damage on young plants, especially caulifowers and summer cabbages. They feed by creating tunnels in the root neck and main root, leading to growth retardation, reduced yield, and even plant death. Larvae also feed on the aboveground part of the plant, creating tunnels in the veins of the leaves. Infested plants often exhibit yellowing, and leaves are drooping. As the infestation progresses, affected plants may become more susceptible to diseases and environmental stressors, further compromising their overall health.
Biological control of cabbage fly with nematodes
Biological control using nematodes can be an effective strategy for controlling cabbage root fly (Delia radicum). Steinernema feltiae is a beneficial entomopathogenic nematode species that is an effective natural enemy of cabbage root fly larvae. The nematodes are applied by spraying or via the irrigation system. After application, the nematodes go in search of larvae, penetrate the larvae, eventually killing them.