Herbicide-Based Weed Management Programs for Palmer Amaranth (Amaranthus palmeri) in Sweetpotato

Abstract

Studies were conducted in 2010 and 2011 to determine the effect of herbicide-based Palmer amaranth management systems in ‘Covington' sweetpotato. Treatments consisted of three herbicide application times. Pretransplant applications were flumioxazin at 107 g ai ha−1, fomesafen at 280 g ai ha−1, flumioxazin at 70 g ha−1plus pyroxasulfone at 89 g ai ha−1, or no herbicide. A second herbicide application was applied within 1 d after transplanting (DAP) and consisted ofS-metolachlor at 800 g ai ha−1, clomazone at 630 g ai ha−1, or no herbicide. Two weeks after planting (WAP) plots receivedS-metolachlor at 800 g ha−1, metribuzin at 140 g ai ha−1, a tank mix ofS-metolachlor at 800 g ha−1plus metribuzin at 140 g ha−1, hand-weeding followed by (fb)S-metolachlor at 800 g ha−1, or no herbicide. Crop tolerance, Palmer amaranth control, and sweetpotato yield in systems containing fomesafen pretransplant were similar to flumioxazin-containing systems. Systems containing flumioxazin plus pyroxasulfone pretransplant resulted in increased crop stunting and decreased sweetpotato yield in 2010, compared with systems containing flumioxazin or fomesafen, but were similar to systems with flumioxazin or fomesafen in 2011. In 2010, systems containingS-metolachlor applied within 1 DAP resulted in increased sweetpotato injury, similar Palmer amaranth control, and reduced no. 1, jumbo, and total sweetpotato yield, compared with systems with clomazone. In 2011, systems containing clomazone were more injurious to sweetpotato than systems receivingS-metolachlor, but Palmer amaranth control and sweetpotato yield were similar. Systems containing metribuzin 2 WAP resulted in increased sweetpotato injury and Palmer amaranth control (in 2010) but similar no. 1 and total sweetpotato yields, compared with systems containingS-metolachlor at 2 WAP. Hand-weeding fbS-metolachlor provided greater Palmer amaranth control and no. 1 sweetpotato yield than did systems ofS-metolachlor without a preceding hand-weeding event in 2010.

Selectivity of pre-emergent herbicides in sweet potato genotypes

“…No death was reported 14 days after transplanting. It means that plants are tolerant to applied herbicides, which corroborates other studies on cultivar under different environmental conditions (Harrison and Jackson 2011;Meyers et al, 2013).…”

“…This fact is probably due to efficient weed control caused by the herbicide and its low toxicity to the crop, as reported by Lugo-Torres and Diaz (2007) and Meyers et al (2013).…”

“…Clomazone, linuron and metribuzin are effective pre-emergent herbicides that could be applied in sweet potato crops (Harrison and Jackson, 2011;Meyers et al, 2013). The tolerance of these herbicides is influenced by the genotype and medium soil residue of approximately 90 days (Lugo-Torres and Díaz, 2007;Shaner, 2014), which is enough time for crops to grow and fully occupy the area, thus avoiding weed interference (Ravi and Saravanan, 2012).…”

Identification and Quantification of Allelochemicals from Selected Sweet Potato (<i>Ipomoea batatas</i> (L.) Lam.) Cultivars

“…In Mississippi, registered herbicides for sweet potato include clomazone, flumioxazin, and S-metolachlor for nutsedge and Palmer amaranth control. Application of clomazone does not adequately control Palmer amaranth [12]; however, flumioxazin provides excellent control of Palmer amaranth, but not of nutsedges [13]. S-metolachlor is effective on yellow nutsedge and Palmer amaranth, however, it also causes significant injury on sweet potatoes, resulting in storage root yield reduction, and decreased storage root quality [5].…”

Sensitivity of Sweet Potato Genotypes to Clomazone and Weed Interference

“…Lugo-Torres and Díaz (2007) evaluated eight sweet potato genotypes in Puerto Rico, with application of 1.12 kg ha -1 of clomazone in pre-emergence, and found no visual symptoms of phytotoxicity at 28 days after transplanting. On the other hand, Meyers et al (2013) reported injuries in the plants caused by this herbicide, however, they found no effect on root yields. These results confirm the selectivity of this herbicide to this crop and the differences in sensitivity of each genotype.…”