Control of Florida Beggarweed (Desmodium tortuosum) in Peanuts (Arachis hypogaea) with Chloramben1

Abstract

Abstract Experiments were conducted in 1983 and 1984 to evaluate control of Florida beggarweed [Desmodium tortuosum (SW) DC.] in peanuts (Arachis hypogaea L.) with chloramben (3-amino-2,5-dichlorobenzoic acid) applied at 2.2 kg ai/ha at ground cracking; and chloramben (with crop oil concentrate included at 2 L/ha) applied at either 0.6, 1.1, 2.2, or 3.4 kg ai/ha, at either 30, 45, 60, 75, or 90 days after planting (DAP). Maximum control (as indicated by weed weight at harvest) was achieved with the ground-cracking treatment, and with postemergence applications of 2.2 kg/ha, or higher applied at 30 DAP. Later applications resulted in progressively less control. Peanuts were tolerant to all rates evaluated, as indicated by yield and grade, provided the application was either before or after the flowering and pegging period (45 to 60 DAP). Growth chamber studies indicated that a spreader-sticker type adjuvant (i.e. a petroleum or vegetable based oil-surfactant blends) was essential for acceptable postemergence activity. Comparisons of autoradiograms prepared from peanuts and Florida beggarweed plants where 14C-chloramben had been applied to the foliage and thin layer chromatographic analysis of foliar extracts indicated that the relative tolerance of peanuts could be attributed to the combined effects of limited absorption and translocation, as well as the enhanced ability of peanuts to convert the absorbed chloramben to a non phytotoxic N-glucosyl conjugate.