Management of Broadleaf Signalgrass (Brachiaria platyphylla) in Peanuts (Arachis hypogaea) with Herbicides

Field studies were conducted in 1978 and 1979 on broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] management in peanuts [Arachis hypogaea (L.) ‘Florigiant′]. In both years, preplant incorporated applications of benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] provided better than 75% initial control of broadleaf signalgrass. Preemergence applications of alachlor and metolachlor provided 90% or better initial control. Vernolate (S-propyl dipropylthiocarbamate) and diphenamid (N,N-dimethyl-2,2-diphenylacetamide) provided less than 45% initial control. An at-cracking application of dinoseb (2-sec-butyl-4,6-dinitrophenol) plus naptalam (N-1-naphthylphthalamic acid) plus either alachlor or metolachlor increased control over that provided by at-planting herbicides alone and maximum yields were obtained. No at-planting herbicide alone provided better than 60% control at harvest and consequently yields were lower. In three of four experiments, sequential applications of at-planting and at-cracking herbicides provided better than 75% control at harvest. In the fourth experiment, only benefin and metolachlor followed by at-cracking applications provided better than 70% control at harvest.