Cabbage Maggot Post
With the warm weather finally arriving, it's important to pay attention to when insect pests will become active so that control measures can be implemented. Cabbage maggot (Delia radicum) is a particular challenge in brassica crop production. It overwinters in the pupal stage, emerging in the spring, usually coinciding with the bloom of yellow rocket and serviceberry. From a growing degree day perspective, emergence begins around 161 Growing Degree Days (GDD) at a base of 4°C, with peak flight occurring around 250 GDD for the first generation of cabbage maggot. As of Tuesday May 19, 2026, 225 GDD (base 4°C) have accumulated in Brooklyn Corner. If you would like to check how many GDD have accumulated in your area go to Perennia’s Farm Data Tools GDD Calculator. Once there, you can select a station close to you, and calculate the GDD accumulation in your area.
Cabbage Maggot Feeding On Roots
Other Delia species, Delia platura (seedcorn maggot), Delia antigua (onion maggot) and Delia florilega (bean seed maggot) are also on the move in the Valley. Once the first generation of adults has emerged in the spring, they take flight and lay their eggs. It is important to know when peak flight is taking place so that you have the opportunity to alter planting times or deploy control measures, such as insect netting, accordingly. For scouting purposes, eggs can usually be found in small clumps on the soil around the base of your seedlings.
Vegetable Specialist | Agricultural Services
Perennia Food and Agriculture Corporation
Email mfageria@perennia.ca
Mobile 902-890-7716
