Goal (oxyfluorfen) [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] or Ronstar (oxadiazon) [2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] each at 2.2 kg ai/ha (2.0 lb/A) controlled 87% and 70% of the summer annual weeds in newly planted liners of ‘Hershey Red’ azaleas (Rhododendron obtusum Planck) when applied at planting in June 1980 and reapplied in March 1981. Ronstar at 4.5 kg/ha (4.0 lb/A) controlled 80% or more of Pennsylvania bittercress (Cardamine pensylvanica Muhl.), common purslane (Portulaca oleracea L.), spotted spurge (Euphorbia maculata L.), common yellow woodsorrel (Oxalis stricta L.), and common groundsel (Senecio vulgaris L.). Devrinol (napropamide) [2-(a-naphthoxy)-N,N-diethylpropionamide] applied at 4.5 or 9.0 kg/ha (4.0 or 8.0 lb/A) was the only effective treatment for controlling common chickweed [Stellaria media (L.) Cyrillo] (81%). Goal at 2.2 kg/ha (2.0 lb/A) and Devrinol at 9.0 kg/ha (8.0 lb/A) were the most effective treatments for controlling large crabgrass [Digitaria sanguinalis (L.) Scop.]. No significant differences were observed in size of the azaleas after two years.
Author notes
Cooperative investigation of the University of Maryland Agric. Expt. Stn. and the U.S. Dept. Agric., Agric., Res. Serv., Expt. Stn. Scientific Article No. A-3780, Contribution No. 6757 of the Maryland Agric. Expt. Stn.
2Associate Professor of Horticulture, University of Maryland-College Park and Research Horticulturist, U.S. Department of Agriculture, ARS, Weed Science Research, Bldg. 1301, Fort Detrick, Frederick, MD 21701.