Cabbage maggot biology & life cycle
Overwinters as pupae with adult flies emerging in late May or June. Eggs are laid in soil near the crop and hatch in one week. Larvae burrow to plant roots and feed for 3-4 weeks. Mature larvae move away from roots to pupate. Adults emerge 2-3 weeks later. Two generations per year. The first generation does the majority of the damage to seedlings by girdling the roots. The outer leaves will yellow and wilt; an indication that the maggots are present. The second generation does not typically kill the host plant, however, it does reduce yield. Injury to roots results in stunted growth or death of plants as root rot organisms will enter the plant. Severe wilting of the leaves, during dry weather is common. Maggot damage can cause canola to lodge.
