The Incorporation of Herbicides into Organic Mulches for Weed Control in Ornamental Plantings1

Abstract

N, N-dimethyl-2, 2-diphenylacetamide (diphenamid) and α, α, α,- trifluoro-2, 6-dinitro-N, N-dipropyl-p-toluidine (trifluralin) caused no injury to transplanted petunias (Petunia hybrida Vilm.) or marigolds (Tagetes patula L.) when incorporated in a mulch. Satisfactory broadleaf and grass weed control as denoted by indicator crops was achieved with both of these herbicides. Dichlobenil, 2,6-dichlorobenzonitrile, caused severe injury to both petunia and marigold transplants when applied in the herbicide-mulch combination. Control of broadleaf and grass indicator weeds with dichlobenil was excellent at all rates. Dimethyl tetrachloro terephthalate (DCPA) resulted in no visible injury to the marigold or petunia transplants when used in the herbicide-mulch combination, but control of grass and broadleaf indicator weeds was poor. When diphenamid and dichlobenil at the same rates were incorporated on peat moss, licorice root, pine bark or sugar cane mulches, no differences were observed among the mulches in regard to their ability to control weed growth. On established nursery stock, 2-chloro-4, 6-bis (ethylamino)-s-triazine (simazine) plus DCPA, simazine plus diphenamid, and 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (diuron), applied directly to the soil surface performed better than the herbicide-mulch combination at the lower rates. At higher rates, both the direct spray on the soil surface and the herbicide-mulch combination performed satisfactorily.