Morningglory (
Peanut is a valuable commodity in the United States with approximately 634,800 ha harvested with an estimated value of $1.19 million USD (
Weed control programs often include preplant incorporated, preemergence, and postemergence (POST) herbicides to minimize interference of weeds with peanut and challenges with harvest (
Carfentrazone-ethyl and pyraflufen-ethyl inhibit protoporphyrinogen oxidase (PPO) in sensitive plants including morningglory (
Field experiments to compare herbicide rate and timings of carfentrazone-ethyl and pyraflufen-ethyl were conducted in North Carolina during 2012, 2013, and 2014 at the Peanut Belt Research Station located near Lewiston-Woodville (36.1323 N, -77.1705W) and at the Upper Coastal Plain Research Station (35.8942N, -77.68011W) located near Rocky Mount. Soil at Lewiston-Woodville was a Norfolk sandy loam (fine loamy, siliceous, thermic, Aquic Paleudalts) with organic matter ranging from 0.5 to 1.2% and pH 6.1. Soil at Rocky Mount was a Goldsboro loamy sand (fine loamy, mixed, semiactive, thermic, Typic Hapludults) with 1.5% organic matter and pH 5.9. The Virginia market type peanut cultivar 'Bailey' (
Peanut response to carfentrazone-ethyl and pyraflufen-ethyl were evaluated in separate experiments. The experiment with carfentrazone-ethyl was conducted at Lewiston-Woodville and Rocky Mount during 2012 and 2013 and during 2014 only at Lewiston-Woodville. Carfentrazone-ethyl (Aim® EC, FMC Corporation, Philadelphia, PA) at 17.5 and 35 g ai/ha was applied 1 and 2 weeks prior to digging peanut pods and inverting vines (WBD). The experiment with pyraflufen-ethyl was conducted at Lewiston-Woodville during 2012, 2013, and 2014. Pyraflufen-ethyl (ET®, Nichino America, Inc., Wilmington, DE) at 1.8 and 3.6 g ai/ha was applied 1 and 2 WBD. The selected herbicide rates were within the registered rate of these herbicides in peanut (
Another experiment was conducted in North Carolina during 2014 at the Border Belt Tobacco Research Station near Whiteville (34.4118 N, -78.7911W) on a Norfolk sandy loam soil and during 2015 in two different fields at Lewiston-Woodville to compare peanut response to carfentrazone-ethyl and pyraflufen-ethyl with diclosulam, lactofen, and 2,4-DB herbicides when applied 4 WBD. The cultivar 'Sullivan' (
All experiments were conducted in conventionally-prepared, raised seedbeds in rows spaced 91 cm apart. Plot size was 2 rows by 6 m long. Peanut cultivar was planted at a seeding rate designed to provide a final in-row population of 12 plants/m. Fertilization, insect, and disease management practices other than specific treatments were standard for peanut production in North Carolina. Experiments were maintained weed free using soil-applied and postemergence herbicides during the season across the entire test area including non-treated plots. Pendimethalin (Prowl H2O herbicide, BASF Corp., Research Triangle Park, NC) at 1.1 kg ai/ha was applied preplant incorporated followed by
In the experiment with carfentrazone-ethyl and pyraflufen-ethyl only, visible estimates of peanut injury were determined 1 and 2 week after treatment (WAT) using a scale of 0 to 100 where 0 =; no injury and 100 =; plant death. Peanut injury 2 WAT was only observed from carfentrazone-ethyl and pyraflufen-ethyl application that was made 2 WBD. Foliar chlorosis, necrosis, leaf defoliation, and plant stunting were considered when making the visible estimates. In the experiment with carfentrazone-ethyl and pyraflufen-ethyl compared with diclosulam, lactofen, and 2,4-DB, visible estimates of peanut injury were determined 2 WAT. Peanut pods were dug and vines inverted based on pod mesocarp color to obtain optimum yield (
Data were subjected to ANOVA using the PROC GLIMMIX procedure in SAS (SAS Institute Inc., Cary, NC) appropriate for the factorial treatment arrangement. Experiments were classified as specific combinations of year and/or location. Means of significant main effects and interactions were separated using Fisher's Protected LSD test at P ≤; 0.05. The non-treated control was included in peanut yield analysis but not in peanut injury.
Peanut injury from carfentrazone-ethyl 1 WAT was influenced by the interaction of experiment by rate (P ≤; 0.0371) and experiment by application timing (P ≤ 0.0001); therefore data are presented by experiments. The interaction of carfentrazone-ethyl rate by application timing was significant for peanut injury 1 WAT for 2014 at Lewiston-Woodville (P =; 0.0010) but was not observed at Lewiston-Woodville and Rocky Mount during 2012 and 2013 (
Peanut injury 1 week after treatment and pod yield as influenced by experiment and carfentrazone-ethyl rate and timing of application.
Peanut injury 2 week after POST application of carfentrazone-ethyl.a
In the experiment with pyraflufen-ethyl, the interaction of experiment × application timing and experiment × herbicide rate were significant for peanut injury at 1 WAT (P ≤ 0.0001) and 2WAT (P = 0.0197). Therefore, data are presented by each year. Peanut injury at 1 WAT was not affected by the interaction of pyraflufen-ethyl rate × application timing for experiments during 2012 and 2013 (P > 0.05); this interaction was significant in 2014 (P < 0.0001) (
Peanut injury 1 week after treatment and pod yield as influenced by experiment and pyraflufen-ethyl rate and timing of application.
Peanut injury 2 week after POST application of pyraflufen-ethyl.a
Peanut yield following carfentrazone-ethyl and pyraflufen-ethyl was not influenced by the main effect of herbicide rate or application timing and their interaction alone or with experiment. Peanut yield was similar to non-treated peanut regardless of herbicide rate or timing of application (
The main effect of herbicide and the interaction of experiment × herbicide were significant for visible injury (P ≤ 0.0001). Although the main effect of herbicide was significant for pod yield, the interaction of experiment × herbicide was not significant (P = 0.3805). Therefore, data are combined over experiments for this interaction. The interaction of experiment × herbicide for visible injury was caused by lower peanut injury at Whiteville following carfentrazone-ethyl compared with pyraflufen-ethyl, and due to lack of differences in injury caused by lactofen and 2,4-DB compared with different results at Lewiston-Woodville (
Peanut injury 2 weeks after treatment and pod yield as influenced by carfentrazone-ethyl, pyraflufen-ethyl, diclosulam, lactofen, and 2,4-DB applied 4 weeks before digging peanut.a
Overall, these results demonstrate that variation in peanut injury can occur depending on rate of carfentrazone-ethyl and pyraflufen-ethyl and application timing. However, when applied within 2 weeks of digging, these herbicides will not reduce peanut yield and may have potential to minimize weed interference with digging and vine inversion.
The North Carolina Peanut Growers Association and FMC Corporation proved financial support for this research. Appreciation is extended to P. D. Johnson, A. T. Hare, T. Buck, and staff at the Border Belt Research Station, the Peanut Belt Research Station, and Upper Coastal Plain Research Station for technical assistance.
First and second author: Postdoctoral Research Scholar and William Neal Reynolds Professor, Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695. Third author: Assistant Professor, Department of Horticultural Sciences, North Carolina State University, Raleigh, NC 27695.