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PEST MANAGEMENT: DISEASES

Broadleaf Weed Control With Carfentrazone-Ethyl Tank Mixtures in Rice

A.T. Ellis, R.E. Talbert, and B.V. Ottis ABSTRACT An experiment was conducted in 2003 to evaluate the performance of carfentrazone-ethyl (Aim) alone and tank-mixed with various broadleaf herbicides. The experiment was conducted at the Rice Research and Extension Center at Stuttgart, Ark., on a Dewitt silt loam. The experimental design was a randomized complete block with four replications. `Francis' cultivar was used in the experiment. There was a natural infestation of barnyardgrass; and hemp sesbania (Sesbania exaltata), pitted morningglory (Ipomoea lacunosa), and northern jointvetch (Aeschynomene virginica) were sown in rows perpendicular to the drilled rice. Treatments were carfentrazone-ethyl alone and carfentrazone-ethyl tank-mixed with each of the following: bentazon (Basagran), acifluorfen + bentazon (Storm), triclopyr (Grandstand), bispyribac-sodium (Regiment), bensulfuron (Londax), propanil (Stam), and halosulfuron (Permit) applied preflood (PREFLD). Carfentrazone-ethyl was also tank-mixed with 2,4-D amine (Savage) and applied 1 week postflood (POFLD). A blanket treatment of clomazone (Command) was applied preemergence (PRE) for control of natural infestations of grass weeds. There was no significant rice injury from the herbicides. Barnyardgrass control ranged from excellent to moderate from early season to late season with all treatments except for clomazone followed by carfentrazoneethyl + bispyribac-sodium and 2,4-D amine for which control remained excellent. Hemp sesbania was controlled by all treatments except carfentrazone-ethyl tank mixtures with bispyribac sodium, bensulfuron, or triclopyr. The bensulfuron mixture controlled hemp sesbania only moderately (76%), and bispyribac-sodium and triclopyr provided poor control. This may be due to an antagonistic effect when mixing these herbicides. Pitted morningglory was controlled by all treatments throughout the duration of the

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study, but control was only moderate (70%) with carfentrazone-ethyl + propanil. Excellent control of pitted morningglory was influenced by addition of the flood. All treatments for northern jointvetch produced moderate to good control at the early rating time. Carfentrazone-ethyl tank mixed with bispyribac-sodium, halosulfuron, 2,4-D amine, or propanil provided good control of northern jointvetch late in the season. There were no significant differences in rice yields among treatments. INTRODUCTION Rice growers are always looking for better ways to lower production costs without reducing yields, and one way this can be done is by tank-mixing herbicides. Tankmixing herbicides with different chemistries improves control and reduces the chances for weeds to become resistant to a herbicide (Bruff and Shaw,1992; Zhang et al., 1995). This also allows control of a broader range of weeds. The lack of broad-spectrum rice herbicides makes tank mixing one of the best management practices in weed control. Weeds such as hemp sesbania, pitted morningglory, and northern jointvetch are broadleaf weeds that pose a threat to rice production. Hemp sesbania has been ranked as one of the top ten troublesome weeds in the South (Dowler, 1997). Northern jointvetch, also known as indigo, is a very prevalent broadleaf weed in rice (Smith, 1968). Pitted morningglory is a broadleaf weed that is becoming a nuisance on rice levees or areas in a field where a flood is not maintained. Carfentrazone-ethyl is a protoporphyrinogen oxidase (PPO) inhibitor produced by FMC Corporation. It is a fast-acting herbicide that controls jointvetch (indian and northern), smartweed, morningglory spp., annual arrowhead, and hemp sesbania. Carfentrazone-ethyl is relatively cheap and tank mixes well with other herbicides. The objective of this study was to look at several other herbicides, new and old, in combination with carfentrazone-ethyl for the control of hemp sesbania, pitted morningglory, and northern jointvetch. PROCEDURES The study was conducted in 2003 at the Rice Research and Extension Center in Stuttgart, Ark. The soil was a Dewitt silt loam (fine, smetic, thermic Typic Albaqualfs) with 1% organic matter, 8% sand, 75% silt, 16% clay, and pH of 5.4. The experimental design was a randomized complete block replicated four times with plots 6 ft wide and 15 ft long. Standard fertilizer rates and cultural methods were used. The rice cultivar `Francis' was drilled at 28.6 lb/acre in nine rows on 6-in. spacings. Seeds of hemp sesbania, pitted morningglory, and northern jointvetch were drilled in rows perpendicular to the rice rows. Carfentrazone-ethyl at 0.025 lb/acre was applied alone and in tank mixture with bentazon + aciflurofen at 0.25 lb/acre, bentazon at 0.75 lb/acre, triclopyr at 0.25 lb/ acre, bispyribac-sodium at 0.032 lb/acre, bensulfuron at 0.032 lb/acre, propanil at 4.0 lb/acre, and halosulfuron at 0.025 lb/acre. Each treatment contained nonionic 111

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surfactant (NIS) at 0.25% V/V and was applied at PREFLD when rice had two tillers. Carfentrazone-ethyl at 0.025 lb/acre was also applied in a tank mixture with 2,4-D amine at 0.25 lb/acre applied postflood (POFLD) when rice had four tillers. A natural infestation of barnyarndgrass (Echinochloa crus-galli) was controlled with clomazone at 0.4 lb ai/acre preemergence (PRE) applied to the entire study area. Herbicides were applied with a CO2 backpack sprayer. Visual efficacy evaluations were taken 6 and 35 days after treatment (DAT). Ratings were based on a 0 to 100% scale, with 0 representing no control and 100 representing complete control. Plots were harvested at rice maturity for yield data. All data were subjected to analysis of variance (ANOVA), and means were separated with Fisher's Least Significant Difference (LSD) at a 0.05 confidence level. RESULTS AND DISCUSSION Barnyardgrass was controlled >80% with all treatments 6 DAT. Control at 35 DAT was moderate (58% to 72%) with all treatments except for carfentrazone-ethyl + bispyribac sodium and carfentrazone ethyl + 2,4-D amine which were 94% and 88%, respectively. Excellent control (>96%) of hemp sesbania 6 DAT was achieved with carfentrazone-ethyl alone, carfentrazone-ethyl + acifluorfen + bentazon, carfentrazone-ethyl + bentazon, carfentrazone-ethyl + propanil, and carfentrazoneethyl + halosulfuron. Carfentrazone-ethyl + 2,4-D amine had not been applied at this time. Carfentrazone-ethyl + triclopyr, carfentrazone-ethyl + bispyribac sodium, and carfentrazone-ethyl + bensulfuron controlled hemp sesbania 88%, 84%, and 90%, respectively, 6 DAT. At 35 DAT carfentrazone-ethyl alone, or with acifluorfen + bentazon, carfentrazone-ethyl + propanil, carfentrazone-ethyl + halosulfuron, carfentrazone-ethyl + 2,4D amine all showed excellent control of hemp sesbania of 100%. Carfentrazone-ethyl + triclopyr, carfentrazone-ethyl + bispyribac sodium, and carfentrazone-ethyl + bensulfuron failed to control hemp sesbania adequately (28%, 46%, and 76%, respectively). This could be due to an antagonistic reaction between carfentrazone-ethyl and the three herbicides. Pitted morningglory was controlled >95% with all treatments except for carfentrazone-ethyl + propanil (70%). Carfentrazoneethyl + 2,4-D amine was not applied at this time. At 35 DAT, complete pitted morningglory control was acheived with all treatments assisted by the flood. Pitted morningglory is not able to withstand a flood due to the lack of arenchyma tissue, which allows for diffusion of oxygen from aerial portions of a plant to the roots. Northern jointvetch control at 6 DAT was 70 to 90% with all treatments. At 35 DAT, complete northern jointvetch control was obtained with carfentrazone-ethyl + bispyribac sodium or carfentrazone-ethyl + halosulfuron. Carfentrazone-ethyl alone, carfentrazoneethyl + acifluorfen + bentazon, carfentrazone-ethyl + bentazon, carfentrazone-ethyl + bensulfuron, and carfentrazone-ethyl + triclopyr all failed to control (22 to 48% control) northern jointvetch effectively 35 DAT. There were no significant yield differences among treatments.

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SIGNIFICANCE OF FINDINGS Carfentrazone-ethyl tank mixed with triclopyr seems to have an antagonistic effect. Tank mixing halosulfuron and 2,4-D amine with carfentrazone-ethyl improved control of all weeds compared to carfentrazone-ethyl alone. Pitted morningglory control was assisted by the addition of the flood. ACKNOWLEDGMENTS FMC Corporation is acknowledged for providing the product and partial support for this study. The study was partially funded by producers' check-off funds through the Arkansas Rice Research Board. LITERATURE CITED Bruff, S.A. and D.R. Shaw. 1992. Tank-mix combinations for weed control in stale seedbed soybean (Glycine max). Weed Technol. 6:45-51. Dowler, C. 1997. Weed survey - southern states: broadleaf crops subsection. Proc. South. Weed Sci. Soc. 48:290-325. Smith, R.J. Jr. and W.C. Shaw. 1968. Weeds and their control in rice production. U.S. Dep. Agric.,Agric. Hand. 292. U.S. gov. Printing Office, Washington, D.C. p. 64. Zhang, J., A.S. Hamill, and S.E. Weaver. 1995. Antagonism and synergism between herbicides: trends from previous studies. Weed Technol. 9:86-90.

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Table 1. Carfentrazone-ethyl tank mixtures for broadleaf weed control in rice at the Rice Research and Extension Center, Stuttgart, Ark. Barnyardgrass 6 DATz ---------------------------------------------------- (%) -----------------------------------------------------0 94 92 68 98 100 98 100 90 48 0 65 0 96 0 98 0 100 0 100 0 70 0 22 35DATz 6 DAT 35 DAT 6 DAT 35 DAT 6 DAT 35 DAT Hemp sesbania Pitted morningglory Northern jointvetch

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88 58 100 100 96 100 82 24 94 68 88 28 96 100 80 32 98 94 84 46 98 100 88 100 88 72 90 76 96 100 80 48 86 62 98 100 70 100 90 68 continued

Herbicide

Application

treatment

Rate

timing

(lb ai/acre)

PRE fb PREFLD

PRE fb PREFLD

PRE fb PREFLD

PRE fb PREFLD

PRE fb PREFLD

PRE fb PREFLD

Nontreated checky Clomazone fb carfentrazone-ethyl + NIS Clomazone fb carfentrazone-ethyl + bentazon + NIS Clomazone fb carfentrazone-ethyl + (acifluorfen + bentazon)x + NIS Clomazone fb carfentrazone-ethyl + triclopyr + NIS Clomazone fb carfentrazone-ethyl + bispyribac sodium + NIS Clomazone fb carfentrazone-ethyl + bensulfuron + NIS Clomazone fb carfentrazone-ethyl + propanil + NIS

0.4 fb 0.025 + 0.25% V/V 0.4 fb 0.025 + 0.75 + 0.25% V/V 0.4 fb 0.025 + 0.25 + 0.25% V/V 0.4 fb 0.025 + 0.25 + 0.25% V/V 0.4 fb 0.025 + 0.038 + 0.25% V/V 0.4 fb 0.025 + 0.038 + 0.25% V/V 0.4 fb 0.025 + 4.0 + 0.25% V/V

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PRE fb PREFLD

Table 1. Continued. Barnyardgrass 6 DATz ---------------------------------------------------- (%) -----------------------------------------------------92 72 98 100 98 100 88 100 35DATz 6 DAT 35 DAT 6 DAT 35 DAT 6 DAT 35 DAT Hemp sesbania Pitted morningglory Northern jointvetch

Herbicide

Application

treatment

Rate

timing

(lb ai/acre)

Clomazone fb carfentrazone-ethyl + halosulfuron + NIS Clomazone fb carfentrazone-ethyl + 2,4-D amine NIS LSD (.05) 98 86 ­w 100 ­ 100 ­ 6 20 5 13 18 0 11

0.4 fb PRE fb 0.025 + PREFLD 0.025 + 0.25% V/V 0.4 fb PRE fb 0.025 + POFLD 0.25 + 0.25% V/V

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B.R. Wells Rice Research Studies 2003

z

y

x

w

Abbreviations: DAT, days after treatment; fb, followed by; PRE, preemergence; PREFLD, application before flood at 2-tiller rice stage; POFLD, application after flood at 4-tiller rice stage. Nontreated plots were not included in analysis. StormTM, a pre-packaged mixture. Not yet applied.

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