Cabbage Maggot
Delia radicum
0 host plants
Last updated
Quick Reference
Cabbage Maggot Emergence (est.) typically begins around 1350 GDD₃₂. As of May 18, 2026, all seven Puget Sound stations have passed this threshold (2022.7–2224.5 GDD₃₂), so Emergence (est.) is likely underway across the lowlands.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of May 18, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,225 | Emergence (est.) | — | — |
| Kent / Auburn | 2,194 | Emergence (est.) | — | — |
| Seattle / UW | 2,164 | Emergence (est.) | — | — |
| Olympia / Tumwater | 2,128 | Emergence (est.) | — | — |
| Bellingham / Whatcom | 2,098 | Emergence (est.) | — | — |
| Tacoma / Puyallup | 2,092 | Emergence (est.) | — | — |
| Sequim / Rain Shadow | 2,023 | Emergence (est.) | — | — |
Source: WSU HortSense; Cornell NEWA cabbage maggot degree-day model. gdd32_estimated: 1200 GDD₃₂ calibrated from Kent 2024-2025 daily min/max cross-computation (300 GDD₄₃ = ~1181-1338 GDD₃₂; midpoint 1200). Replaces scalar approximation (value/1.10). AUDITOR.md Rec C, 2026-05-18. About GDD₃₂ →
Monitoring & Action
Yellow sticky traps near brassica beds catch adult flies. Wilting or yellowing plants with no above-ground pest visible suggest root maggot feeding; pull plant to inspect roots.
Preventive management (row covers) deployed before adult emergence is more effective than reactive treatment.
Larvae tunnel into roots and underground portions of stems. Causes yellowing, wilting, and stunting of foliage. Soft rots often follow larval feeding damage, compounding injury. Severe damage can kill plants.
Cultural Controls
- Floating row covers deployed at seeding or transplanting, before adult fly emergence, are the most effective control
- Crop rotation: do not plant brassicas in the same bed that grew brassicas the previous year; pupae overwinter in soil where they grew
- Avoid placing row covers over soil previously infested with cabbage maggot pupae
- Delay spring planting of brassicas until after first-generation fly peak where feasible