Control of Florida Beggarweed and Sicklepod in Peanuts with Dinoseb1

Abstract

Abstract Florida beggarweed (Desmodium tortuosum (Sw.) DC.) and sicklepod (Cassia obtusifolia L.), two of the worst weeds in peanuts grown in the Southeastern states, were most susceptible to dinoseb (the alkanolamine salt of 2-sec-butyl-4, 6-dinitrophenol) applied to seedlings before the true leaves expanded. If either of these weeds was not controlled by the first application of dinoseb, especially at the lowest rate of 0.63 kg/ha, it often survived later applications and became a problem when harvesting the peanuts. Sicklepod growing in soil previously treated with vernolate (S-propyl dipropylthiocarbamate) was more susceptible to low rates of dinoseb than sicklepod growing in soil free of vernolate. A single treatment of dinoseb at 0.63 kg/ha killed seedling Florida beggarweed if the maximum daily temperature exceeded 32C; however, twice that rate was necessary under cool conditions. Repeated treatments with higher rates (such as 1.26 kg/ha) of dinoseb usually were necessary for satisfactory control of sicklepod. However, where dinoseb did not kill the early weeds, repeated treatments suppressed weed growth and reduced the mass of weeds present at harvest. Peaunt plants generally tolerated the repeated dinoseb treatments, although yields trended lower if dinoseb at 1.26 kg/ha was applied after treatment with naptalam (N-1-naphthylphthalamic acid). However, any reduction in yields of peanuts attributable to either naptalam or dinoseb treatments was much less than potential reductions in yield from uncontrolled sicklepod and Florida beggarweed.