EFFECT OF SEVERAL HERBICIDES ON GERMINATION, SURVIVAL, AND EARLY GROWTH OF CARAGANA AND ON WEEDS

Abstract

Several pre-emergence herbicides were tested, both in the greenhouse and in the field, for tolerance to germinating and 1-year-old seedlings of caragana (Caragana arborescens Lam.) and for effectiveness in controlling weeds.Dinoseb (4,6-dinitro-o-sec-butylphenol) and its alkanolamine salt at 8 lb/ac, trifluralin (alpha, alpha, alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 4 to 6 lb/ac, DCPA (dimethyl 2,3,5,6-tetrachloroterephthalate) at 15 lb/ac, swep (methyl 3,4-dichlorocarbanilate) at 6 to 9 lb/ac, and Tenoran (N-4-(p-chlorophenoxy)-phenyl-1,1-dimethylurea) at 6 lb/ac gave satisfactory weed control with no injury to germinating caragana seedlings. Liquid formulations of dinoseb or dinoseb-amine were more effective than the granular dinoseb formulation at rates of 8 lb/ac or less. Mixtures of dinoseb, trifluralin, and DCPA were also effective and these may be used where a wider weed species spectrum is encountered.Trifluralin at 6 lb/ac and mixtures of granular dinoseb at 8 to 12 lb/ac with DCPA at 10 lb/ac also provided satisfactory weed control with no injury to 1-year-old caragana seedlings.In the greenhouse tests, pre-emergence applications of trifluralin, diphenamid (N,N-dimethyl-2,2-diphenylacetamide), swep, DCPA, and DMPA (Q-(2,4-dichlorophenyl) O-methyl isopropylphosphoramidothioate) did not retard the germination of weed seeds, but the young weed seedlings were either killed or retarded in growth as the experiments progressed. On the other hand, linuron (3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea), dichlobenil (2,6-dichlorobenzonitrile), and dinoseb affected the emergence of weed seedlings. The weeds surviving the dinoseb treatment grew well. Hand-weeding stimulated the germination of more weed seeds.