Management Options and Factors Affecting Control of a Common Waterhemp (Amaranthus rudis) Biotype Resistant to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Abstract

Repeated use of protox-inhibiting herbicides has resulted in a common waterhemp (Amaranthus rudisSauer) biotype that survived lactofen applied up to 10 times the labeled rate. Field and greenhouse research evaluated control options for this biotype of common waterhemp. In the field, PRE applications of flumioxazin at 72 g ai ha−1, sulfentrazone at 240 g ai ha−1, and isoxaflutole at 70 g ai ha−1controlled common waterhemp >90% up to 6 weeks after treatment. POST applications of fomesafen at 330 g ai ha−1, lactofen at 220 g ai ha−1, and acifluorfen at 420 g ai ha−1resulted in <60% visual control of common waterhemp, but differences were detected among herbicides. In the greenhouse, glyphosate was the only herbicide that controlled protox resistant waterhemp. The majority of herbicide activity from POST flumioxazin, fomesafen, acifluorfen, and lactofen was from foliar placement, but control was less than 40% regardless of placement. Control of common waterhemp seeded at weekly intervals after herbicide treatment with flumioxazin, fomesafen, sulfentrazone, atrazine, and isoxaflutole exceeded 85% at 0 weeks after herbicide application (WAHA), while control with isoxaflutole was greater than 60% 6 WAHA. PRE and POST options for protox-resistant common waterhemp are available to manage herbicide resistance.

A novel mutation A212T in chloroplast Protoporphyrinogen oxidase (PPO1) confers resistance to PPO inhibitor Oxadiazon in Eleusine indica

“…Shoup and Al‐Khatib stated that postemergence applications of acifluorfen and lactofen inhibited PPO‐resistant A. tuberculatus 40%, while preemergence applications of sulfentrazone and flumioxazin inhibited the resistant population greater than 85%. Another case showed that preemergence applications of flumioxazin and sulfentrazone controlled a resistant A. tuberculatus biotype 90%; however, postemergence applications of other PPO inhibitors controlled less than 60% . Researchers have also noted that different resistant levels vary between different PPO inhibitor chemical families.…”

“…Another case showed that preemergence applications of flumioxazin and sulfentrazone controlled a resistant A. tuberculatus biotype 90%; however, postemergence applications of other PPO inhibitors controlled less than 60%. 29 Researchers have also noted that different resistant levels vary between different PPO inhibitor chemical families. Shoup et al 13 found that sulfentrazone slightly injured the lactofen-resistant A. tuberculatus biotype.…”

Herbicide resistance in Amaranthus tuberculatus†

“…Another factor potentially contributing to the apparent explosion in resistance to PPO inhibitors is that preemergence use of these herbicides (which also decreased during the glyphosate-resistant-crop era but not as much as their use postemergence) was continuing to increase the frequency of resistance, but this was going unnoticed. 23 PPO inhibitors applied preemergence were reported to provide effective control of A. tuberculatus populations that were resistant to these same herbicides applied postemergence, 50 leading to the misconception (which still persists) that the PPO G210 deletion confers resistance to PPO inhibitors applied postemergence but not preemergence. Further work has conclusively demonstrated, however, that plants with ΔG210 are less sensitive to PPO inhibitors regardless of the application timing.…”

Annual Bluegrass (Poa annua) Biotypes Exhibit Differential Levels of Susceptibility and Biochemical Responses to Protoporphyrinogen Oxidase Inhibitors

“…However, PRE applications of sulfentrazone and flumioxazin controlled this biotype >85%. Similarly, PRE applications of flumioxazin, isoxaflutole, and sulfentrazone controlled an R-biotype of A. tuberculatus >90%, while POST applications of other PPO inhibitors provided <60% control (Harder et al 2012). It was also found that the majority of herbicide activity from POST flumioxazin, fomesafen, acifluorfen, and lactofen was from foliar placement, but control was less than 40% at all placements.…”