Yield and Quality Constraints of Cabbage Planted in Rye Mulch

The impact of cereal rye (Secale cereale L.) mulch or a mixture of rye mulch and red clover (Trifolium pratense L.) on weeds, insect pests and 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 residue, or by mowing the rye and then seeding red clover into the rye residue. Initial suppression of most weed species by rye or rye/clover mulch was similar to that resulting from conventional tillage where trifluralin was used. Supplemental weed control was necessary in the rye plots later in the season. Early dandelion (Taraxacum officinale Weber) infestation from windblown seeds was a problem in rye mulch in 1995. Redroot pigweed (Amaranthus retroflexus L.) and velvetleaf (Abutilon theophrasti Medicus) were significantly reduced by the rye mulch. Cabbage grown in rye mulch had lower insect pest populations than cabbage under conventional tillage. The lower populations of diamondback moth (Plutella xylostella (L.)), imported cabbage worm (Pieris rapae (L.)), cabbage looper (Trichoplusia ni (Hübner)) and aphids (primarily Myzus persicae (Sulzer) and Lipaphis erysimi (Kaltenbach)) in rye mulch may 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 treated with Bt-insecticide had the lowest insect damage ratings of any treatment but yields were still lower than those obtained in conventional tillage. Improvements in insect and weed control occurred at the expense of severe yield losses due to difficulties in cover crop management: poor kill of rye, soil compaction during mowing, and competition by red clover.