IMPACT OF CRUCIFEROUS TRAP CROPS ON LEPIDOPTERAN PESTS OF CABBAGE IN HAWAII

The objective of this study was to determine if trap crops of Indian m ustard, Brassica juncea (L.) Czern., and 'Tastie' head cabbage, Brassi ca oleracea variety capitata L., gown alongside a main crop of 'Scorpi o' head cabbage would significantly reduce lepidopteran pest numbers a nd improve yields on the main crop. For the 2 most economically import ant lepidopteran pests in the trials, diamondback moth, Plutella xylos tella (L.), and imported cabbageworm, Pieris rapae (L.), significantly higher numbers were found on trap-cropped Scorpio than on monoculture Scorpio for certain key sampling dates. Numbers of Plutella xylostell a were higher on the trap crops than on trap-cropped Scorpio for certa in key dates. It appears that Indian mustard and Tastie cabbage acted effectively as attractants, but through an undetermined mechanism cont amination of the adjacent Scorpio crop occurred. There were no signifi cant differences in yield or marketability between monoculture Scorpio and trap-cropped Scorpio. Various changes in agroecosystem management might allow the attractiveness of the trap crops to be used in a bene ficial manner. Indian mustard and Tastie cabbage show potential for us e as trap crops for Hellula undalis (F.), cabbage looper, Trichoplusia ni (Hubner), and green garden looper, Chrysodeixis eriosoma (Doubleda y). An understanding of the mechanisms that explain the movement of Le pidoptera within vegetationally diverse agroecosystems would be useful for on-farm implementation of this technique. Problems inherent in fi eld experiments that compare the effects of different cropping systems on mobile insect populations are also discussed.