Control of Quackgrass(Agropyron repens)in Highbush Blueberries(Vaccinium corymbosum)and Hybrid Rhododendron(RhododendronX)

Abstract

Quackgrass [Agropyron repens(L.) Beauv.] was controlled by spring application of pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] in 1970 and 1971, but when spring rainfall was below nornal in 1973, only pronamide applied the previous fall gave control. Terbacil (3-tert-butyl-5-chloro-6-methyluracil) gave 90% control of quackgrass for 2 yr at 2.2 kg/ha. Some control continued for 3 yr at 4.5 kg/ha. Three applications of glyphosate [N-(phosphonomethyl)glycine] at 3 kg/ha applied during a 2-yr period controlled quackgrass 97 to 100%. Phytotoxicity was not observed on 14-yr-old highbush blueberries(Vaccinium corymbosumL.) from pronamide or terbacil, on 4-yr-old blueberries from pronamide, or on 2-yr-old rhododendrons(Rhododendron× ‘A. Bedford’) from dichlobenil (2,6-dichlorobenzonitrile), pronamide, or directed sprays of glyphosate or amitrole (3-amino-s-triazole).