Sequential Herbicide Applications for Weed Control in Azaleas

in HortScience
Authors:
C. Edward BesteDepartment of Horticulture, University of Maryland, College Park, MD 20742

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J. Ray FrankAgricultural Research Service, U.S. Department of Agriculture, Weed Science Research, Bldg. 1301, Fort Detrick, Frederick, MD 21701

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Abstract

Sequential applications of granular oxyfluorfen (2 G) at 3.3 kg a.i.·ha−1, oxadiazon (2 G) at 3.3 kg a.i.·ha−1, napropamide (10 G) at 4.5 kg a.i.·ha−1, and chlorpropham (20 G) at 1.1 kg a.i.·ha−1 were evaluated for weed control in newly planted Rhododendron obtusum (Lindl.) Planch cv. Hinocrimson azaleas in the field. Granular oxyfluorfen, oxadiazon, or napropamide applied twice per season controlled 99%, 77%, or 73% of the weeds, respectively, for 2 years. A combination of napropamide, oxyfluorfen, and oxadiazon applied twice per season controlled >99% of the weeds at the season's end. Single seasonal applications of oxyfluorfen or oxadiazon controlled 63% and 77% of the weeds, respectively. Phytotoxicity to azaleas was not observed with any treatment. Chemical names used: 2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyel)benzene (oxyfluorfen); 3-[2,4-dichloro-5-(l-methylethoxy)phenyl]-5-(l,l-dimethylethyl)-l,3,4-oxadiazol-2(3 H)-one (oxadiazon); 2-(α-napththoxy)-N,N-diethylpropionamide (napropamide); and 1-methylethyl 3-chlorophenyl carbamate (chlorpropham).

Contributor Notes

Received for publication 17 Apr. 1985. Cooperative investigation of the Univ. of Maryland Agricultural Experiment Station and the ARS/USDA Service Experiment Station Scientific Article No. A-4054, Contribution No. 7039 of the Maryland Agricultural Experiment Station. We express our appreciation to Chesapeake Nurseries in Salisbury, Md., for providing ground beds and azaleas for this research. Technical assistance by Barbara Abbott, Pat Bagley, Annemarie Edwards, Teresa Rice, and Paul Roberts is greatly appreciated. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

Associate Professor of Horticulture.

Research Horticulturist.

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