effect of interplanting of necteriferous plants on the population density and parasitism of cabbage pests

Nectariferous plants were interplanted with cabbage to examine their effects on the population density and parasitism of cabbage pests, including the imported cabbageworm (ICW), Pieris rapae (L.), cabbage looper (CL), Trichoplusia ni (Hubner), diamondback moth (DBM), Plutella xylostella (L.), and cabbage aphid (CA), Brevicoryne brassicae (L.). Mean parasitism of ICW larvae by Cotesia glomerata (L.) and Lespesia sp. ranged from 6.84 to 28.59% in 1993 and from 15.97 to 27.60% in 1994. ICW larvae collected from cabbage plants that were adjacent to Good Bug Blend plots in 1993 and buckwheat and vetch plots in 1994 had the highest parasitism. Mean parasitism of CL larvae by Patrocloides mantanus (Cresson) and Voria ruralis (Fallen) ranged from 0 to 28.88% in 1993 and from 0.01 to 1.99% in 1994. CL larvae collected from plants grown adjacent to dill plots in 1993 and alyssum and control plots in 1994 had the highest parasitism. Mean percentage parasitism of DBM larvae by Diadegma insulare (Cresson) ranged from 6.18 to 19.13% in 1993 and from 9.43 to 14.94% in 1994. Highest parasitism of DBM was observed in larvae collected from plants adjacent to vetch, Good Bug Blend, and dill plots in 1993 and buckwheat, alyssum and control plots in 1994. Mean percentage of parasitized cabbage aphid, Diaeretiella rapae (M'Intosh), ranged from 4.78 to 11%. Cabbage plants that were adjacent to buckwheat had the highest number of parasitized aphids. Our results add to those of previous research indicating that interplanting or intercropping may enhance a natural enemy's activity against pest species.