| Bell pepper, an economically important vegetable crop in Florida, cannot be grown successfully without controlling yellow nutsedge. Methyl bromide, the only chemical used in polyethylene-mulched bell pepper production that effectively controls nutsedges, is being phased out of production. Information, therefore, is needed for developing alternative yellow nutsedge control measures. Objectives of this research were to determine the number of nutsedge plants tolerated by bell pepper, the time period when yellow nutsedge must be controlled, the distance between nutsedge and bell pepper plants at which pepper yields are reduced, and the activity of 1,3-dichloropropene (1,3-D) + 35% chloropicrin (Pic) and metam-Na on tubers at varying stages of growth. In field experiments, bell pepper and yellow nutsedge plants were grown on polyethylene-mulched, drip-irrigated beds. Respective treatments in the density, critical period, and distance experiments included initial nutsedge tuber densities (ranging from 10 to 120 tubers·m−2), duration of yellow nutsedge interference with pepper and nutsedge-free time (0 to 13 weeks after pepper transplanting), and initial distance between nutsedge plants and a pepper plant (7.6 to 30.5 cm). In the greenhouse experiment, 1,3-D + Pic or metam-Na was applied to dry, imbibed, and sprouted nutsedge tubers. Bell pepper yield losses of greater than 10% were predicted with interference of nutsedge plants from 5 tubers·m−2. Nutsedge-free periods of 4 to 5 weeks or 1½ to 6½ weeks after pepper establishment were required in spring and fall, respectively, for not more than 10% loss of marketable pepper fruits. All distances of planted tubers from a pepper plant of 7.6 to 30.5 cm resulted in greater than 10% reductions in pepper fruit yield. In the greenhouse experiment, metam-Na and 1,3-D + Pic effectively controlled yellow nutsedge for 28 days. Tubers imbibed with water before planting were more susceptible to 1,3-D + Pic than tubers planted without prior water imbibition. Near total suppression of nutsedge tubers was needed for a longer period of time in fall than spring to obtain adequate pepper yields. When nutsedge tubers were planted 5 or 10 cm apart, suppression of nutsedge needed to extend to the edge of the 61 cm-wide planting beds. The efficacy of 1,3-D + Pic and metam-Na against yellow nutsedge was enhanced by minimizing volatilization of fumigant gasses, and the efficacy of 1,3-D + Pic enhanced when applied to water-imbibed tubers. Polyethylene-mulched bell pepper exhibited a low tolerance of yellow nutsedge in the plant bed, and acceptable fruit production required the absence of nutsedge from early- through mid-season. |
