Pre plant and pre- emergence herbicides are commonly used in lettuce production. We investigated possible effects the herbicides benefin (Balan), pronamide (Kerb) and bensulfide (Prefar) had on emergence and seedling growth of several iceberg lettuce varieties that had been primed and pelleted by seed enhancement companies The herbicide Prefar and a mixture of Balan + Prefar had the greatest impact on dry weight regardless of variety, while seedlings grown on Kerby plots were not significantly different than seedlings from untreated plots. Dry weight accumulation and field emergence were influenced significantly by pellet types and priming methods.

Lettuce plants (Lactuca sativa L. var. Ithaca) were transplanted on different beige and black paper mulches and on a coextruded white/black polyethylene mulch in organic soil in 1997 and 1998. Non-weeded and weeded control plots were also used. Plant mortality in 1997 for plants grown on bare soil was 10 to 15% greater than that of mulched plants. Head weight was found to be 3.6 times (1997) and 12 times (1998) greater for lettuce grown on mulch compared with a weeded control. The transmission, reflection and absorption of light of the white/black polyethylene mulch and black paper mulch remained stable over the course of the experiment while those of the other papers changed over time. Paper mulch decomposition occurred during the experiment. Although, black paper mulch was the only mulch that gave complete control of weed growth, weed populations present under the beige papers were too small in terms of the size and number of weeds to cause lettuce yield reduction.

No description available.

Inter-row mechanical cultivation was proposed as a supplement to or substitute for conventional weed control methods currently used in snap bean, carrot and lettuce production. Several types of cultivators were assessed and compared. The effect of mechanical cultivation on crop yield and quality was studied by counting, weighing and grading bean pods, carrot roots and lettuce heads. The effect of mechanical cultivation on disease incidence was studied by surveying fields during the season and by determining the number and weight of diseased pods, roots and heads at harvest. The relationship between the level of Cercospora blight on carrots and potential impacts on yield was also investigated by measuring plant characteristics and the amount of force needed to separate carrot foliage from root. The effect of mechanical cultivation on the phenology of snap bean flowering was studied by determining how long it took for a plant to produce 50% of its flowers and counting how many flowers and pods a plant produced. In general, mechanical cultivation did not affect normal crop production and may be used to replace or complement conventional weed control methods. There was little variation among different cultivators within one season, but cultivator effects differed among crops and from one year to the next.

No description available.