Enhanced natural regulation of the belowground pest Delia radicum in organic farming systems

Population dynamics of the cabbage root fly Delia radicum in three different organic and one conventional cabbage cropping systems were evaluated over 3 years. Oviposition was reduced over time, but not affected by organic farming practice. Pupal production was reduced in all organic systems compared to the conventional system in all years, but pupal parasitation rates were similar among systems. More predators of fly eggs were present in the organic system O2. Reduced larval survival rates in the organic systems may be result of increased natural enemy activity and plant effects.