YIELD AND QUALITY CONSTRAINTS OF CABBAGE PLANTED IN RYE MULCH

The impact of cereal rye (Secale cereale L.) mulch or a mixture of rye mulen and red clover (Trifolium pratense L.) on weeds, insect pests a nd diseases of cabbage (Brassica oleracea var. capitata L. cv. 'Market Prize') was investigated. Autumn-planted rye was killed the following spring either with glyphosate and then mowed and left as a plant resi due, or by mowing the rye and then seeding red clover into the rye res idue. Initial suppression of most weed species by rye or rye/clover mu lch was similar to that resulting from conventional tillage where trif luralin was used. Supplemental weed control was necessary in the rye p lots later in the season. Early dandelion (Taraxacum of officinale Web er) infestation from windblown seeds was a problem in rye mulch in 199 5. Redroot pigweed (Amaranthus retroflexus L.) and velvetleaf (Abutilo n theophrasti Medicus) were significantly reduced by the rye mulch. Ca bbage grown in rye mulch had lower insect pest populations than cabbag e under conventional tillage. The lower populations of diamondback mot h (Plutella xylostella (L.)), imported cabbage worm (Pieris rapae (L.) ), cabbage looper (Trichoplusia ni (Hubner)) and aphids (primarily Myz us persicae (Sulzer) and Lipaphis erysimi (Kaltenbach)) in rye mulch m ay have been related to the smaller size and lower head weights of the plants. Applications of a microbial insecticide derived from Bacillus thuringiensis (Bt) controlled diamondback moth populations adequately but not cabbage loopers in 1995. Cabbage planted in rye mulch and tre ated with Bt-insecticide had the lowest insect damage ratings of any t reatment but yields were still lower than those obtained in convention al tillage. Improvements in insect and weed control occurred at the Ex pense of severe yield losses due to difficulties in cover crop managem ent: poor kill of rye, soil compaction during mowing, and competition by red clover.