Weed control efficacy of organic mulches as well as a copper hydroxide-coated geotextile (fabric) disk was examined using Rhaphiolepis indica L. or Callistemon citrinus [(Curtis) Stapf] growing in containers. Rout (oxyfluorfen plus oryzalin) and corn gluten meal were included as herbicide treatments. In a second experiment, the effect of subirrigation versus surface irrigation and different depths of pine bark mulch on weed control was studied. In the mulch/herbicide studies, all of the mulch treatments, including the geotextile disk, provided broadleaf weed control, but not annual bluegrass control, similar to that of Rout. Broadleaf weeds were not controlled by corn gluten meal. Although though the number of grass seedlings was reduced 49% from that of the control, Rout reduced the number by 89%. In the mulch depth/irrigation study, mulching reduced weed weight by 92% over that of the control (no mulch and surface irrigated) 8 weeks after transplanting. Subirrigation reduced the number of weeds by at least 95% over that of the control.

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Author notes

This research was funded in part by grants from the University of California Statewide IPM Project and the California Association of Nurserymen.

2Area Integrated Pest Management Advisor. University of California Statewide IPM Project.

3Associate Specialist. Department of Plant Sciences, University of Arizona, Tucson, AZ 85721.

4Weed Science Specialist. Department of Vegetable Crops, One Shields Ave., University of California, Davis, CA 95616.