Broccoli growth parameters and level of head infestations in simple and mixed plantings: Impact of increased flora diversification

The impacts of interplanting broccoli, Brassica oleracea var. italica L., w ith chili pepper, Capsicum annuum L., or yellow sweetclover (YSC), Melilotu s officinalis L., on broccoli growth parameters and levels of lepidopteran head infestations were studied during two field seasons (winter & summer). During both seasons, several broccoli growth characteristics (e.g. plant ve rtical area, whole plant biomass, etc.) were significantly reduced in brocc oli-YSC habitats. However, broccoli heads in broccoli-YSC habitats did not differ significantly in size from other treatment habitats. Additionally, t hese heads contained the lowest mean lepidopteran contaminants per broccoli crown during the winter season. During this period, the average number of lepidopteran contaminants per broccoli head was more than twice that in mon oculture and pepper intercropped broccoli than in broccoli-YSC habitats. Du ring the summer experiment, the average number of lepidopteran contaminants per broccoli head was greater in pepper intercropped broccoli than in both monoculture and YSC interplanted broccoli. Potential causes of broccoli gr owth differences and their relationship to lepidopteran ovipositional behav ior are discussed.