ABSTRACT

EXPERIMENT 1. A field experiment was conducted in 1992 at two locations, Tifton and Plains GA, to determine Buctril efficacy on annual broadleaf weeds. Weed species evaluated included Florida beggarweed (Desmodium tortuosum), smallflower morningglory (Jacquemontia tamnifolia), sicklepod (Cassia obtusifloia), hemp sesbania (Sesbania exaltata), jimsonweed (Datura stramonium), velvetleaf (Abutilon theophrasti), wild radish (Raphanus raphanistrum), prickly sida (Sida spinosa), pigweed species which included redroot, smooth, and spiny (Amaranthus retroflexus, hybirdus, and spinosus, respectively), and a complex of Ipomoea hederacia, lacunosa, coccinea, purpurea, and hederacea var. integriuscula, respectively). Buctril was applied at 0.25, 0.38, 0.50, 0.75, 1.00, and 1.50 lb ai/ac in a factorial arrangement with three different weed sizes: 1-3", 3-4", and 4-6". All herbicide rates are expressed as lb ai/ac.

Buctril gave complete control of hemp sesbania and jimsonweed at 0.25 on weeds up to 6' in height. Complete Florida beggarweed control was achieved at 0.25 on weeds up to 4" tall. Velvetleaf, wild radish, Ipomoea morningglories, and smallflower morningglory were controlled at the 0.25 rate when weed size #4'. There were no differences in Ipomoea morningglory species sensitivity to Buctril. When these species where 4-6' tall, complete control was achieved at 0.5-0.75. Prickly sida control was adequate ($80%) when 1-3" tall. Control of larger prickly sida ($80%), 3-6", required 0.75. Pigweed control ($75%) required at least 0.75 when in the 1-3". For pigweed $3" tall, $1.0 was required for adequate control. Sicklepod control (#60%) was not achieved with any Buctril rates.

EXPERIMENT 2. Buctril and POST grass herbicides (graminicides) were evaluated alone, in tank mixture, and as sequential applications in 1991 at Attapulgus and Smithville, GA and in 1992 at Tifton, GA to determine the effectiveness of each application. Grasses evaluated included Texas panicum (Panicum texanum) and rhizome johnsongrass (Sorghum halepense). The POST treatments were Buctril at 1.50, Select at 0.10, Poast Plus at 0. 19, Assure H at 0.05, and Fusilade 2000 at 0.19 lb/ac applied either 1)alone, 2) tank mixed 3) as a +24 hour sequential with Buctril applied first, and 4) as a +24 hour sequential with the graminicide applied first. All herbicide rates are expressed as lb ai/ac. A nonionic surfactant at 0.25% (v/v) was included with all applications. Buctril + Select tank mixtures displayed some antagonism for Texas panicum control. When tank mixed with Poast Plus, Fusilade 2000, or Assure II, there was no antagonism for Texas panicum control. For all combinations of Buctril and graminicides either as a tank mixed or as +24 hour sequential applied to rhizome johnsongrass, there was a reduction in rhizome johnsongrass control compared to the control from graminicides applied alone. Graminicides applied alone averaged between 50-70% control of rhizome johnsongrass while tank mixture or the + 24 hour sequential generally reduced control to less than 35 %.