Herbicide Effectiveness, Soil Residues, and Phytotoxicity to Peach Trees

Abstract

Dichlobenil (2,6-dichlorobenzonitrile), 3- tert -butyl-5-chloro-6-methyluracil (terbacil), and 3- tert -butyl-5-bromo-6-methyluracil (hereinafter referred to as DP-733) were applied annually for 3 years as soil surface or incorporated treatments for weed control in young peach ( Prunus persica (L.) Batsch., var. Redhaven) trees. Average monthly ratings showed significant increases in bermudagrass ( Cynodon dactylon (L.) Pers.) control with incorporation of all three herbicides. Treetrunk diameters in incorporated dichlobenil plots were greater than those in surface-applied dichlobenil plots. Incorporation in the soil reduced loss of dichlobenil, terbacil, and DP-733. The herbicides did not accumulate in the 0 to 15-cm soil layer. Low concentrations were detected in the 30 to 60-cm soil depth 1 year after the third annual application of 6.72 kg/ha of dichlobenil and 4.48 kg/ha of DP-733. Terbacil was not present in detectable amounts at 30 to 60 cm but was present in the 15 to 30-cm layer of 4.48 kg/ha plots.