Higher Efficiency in Organic than in Conventional Management of Biological Control in Horticultural Crops in North-Eastern Italy

This research analyzes the efficiency of natural pest control in horticultural crops (Red chicory and White cabbage) within different regimes (organic and conventional). Agroecosystem food-web structure was examined in conventional and organic fields, in north-eastern Italy, considering phytophagous, parasitoid and hyperparasitoid guilds. Natural control agents were analysed, especially parasitoids of Plutella xylostella (L.) (Lepidoptera: Plutellidae), one of the most problematic pests on cabbage crops. Phytophagous communities were more diverse and more predators and parasitoids were present in organic than in conventional farms. The parasitization of P. xylostella was significantly higher and the food-web structure was also more complex in organic than in conventional fields. Even with lower spray inputs, organic fields often supported a less abundant phytophagous community than conventional fields, even though the crop damage was similar in both management systems. The present data seem to indicate that the higher presence of biological control agents (predators and parasitoids) in organic fields is effective in moderating crop pest populations.