PEST MANAGEMENT: WEEDS
RicePyr LC ® for
Broadleaf Weed Control on Levees
J.K. Norsworthy, S. Bangarwa, G. Griffith, M.J. Wilson, J. Still, and R.C. Scott
ABSTRACT
RicePyr LC® is a product mixture of propanil and triclopyr that will be marketed
in 2009 for weed control on rice levees. Research was conducted at three locations in
Arkansas in 2008 to determine the rate of RicePyr LC® needed for effective broadleaf
weed control. Two rates of RicePyr LC® were compared to a standard treatment of
SuperWham (propanil) at 2 qt/acre plus Grandstand (triclopyr) at 0.67 pt/acre. RicePyr
LC® at 3 qt/acre, the highest rate evaluated, provided effective control of hemp sesbania,
Pennsylvania smartweed, entireleaf morningglory, ivyleaf morningglory, pitted morningglory, and Palmer amaranth when applied to weeds no more than 12 in. tall or 12-in.
runners. Weed control with RicePyr LC® at 3 qt/acre was comparable to the standard
treatment for all species evaluated, except eclipta which was not adequately controlled
as well with Superwham plus Grandstand. Neither rate of RicePyr LC® injured the rice
growing on the treated levees. Hence, RicePyr LC® appears to be effective option for
broadleaf weed control on rice levees when weeds are small at application.
INTRODUCTION
Weed control on rice levees is one of the most daunting tasks rice producers face
each year (Norsworthy et al., 2007). Saturated soil on levees is conducive for continual
weed emergence, even after establishment of the permanent flood within bays. Often,
two or more herbicides applied jointly are needed to maintain a high level of weed
control on levees. RicePyr LC®, a mixture of propanil (3 lb ai/gal) and triclopyr (0.33
lb ai/gal), will be marketed in rice in 2009 for economical, broad-spectrum control of
broadleaf weeds on levees.
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An experiment was conducted at three sites in 2008 to evaluate the effectiveness
of RicePyr LC® for broadleaf weed control on rice levees.
PROCEDURES
Experiments were conducted at the Arkansas Pine Bluff Farm (APBF) near
Lonoke, the Pine Tree Branch Station (PTBS) near Colt, and the Rice Research and
Extension Center (RREC), near Stuttgart, Ark. ‘Wells’ rice was broadcast-seeded on
2-ft tall levees at 120 lb/acre, with 10 ft between levees. Plots were 30 ft in length and
replicated four times. Herbicide treatments evaluated were RicePyr LC® at 2 qt/acre
(propanil at 1.5 lb ai/acre plus triclopyr at 0.165 lb ai/acre), RicePyr LC® at 3 qt/acre
(propanil at 2.25 lb/acre plus triclopyr at 0.25 lb/acre), and a standard treatment of
SuperWham at 2 qt/acre plus Grandstand at 0.67 pt/acre (propanil at 2.0 lb/acre plus
triclopyr at 0.25 lb/acre). Crop oil concentrate was added to all herbicide treatments at
1% (v/v), and herbicides were applied at 15 or 20 gal/acre. A nontreated control was
included. Treatments were applied when the largest weed was 6- to 12-in. tall or had
6- to 12-in. runners (morningglories). Weed control and crop injury were rated at 2
and 4 weeks after treatment (WAT). All data were subjected to analysis of variance,
and means were separated using Fisher’s protected Least Significance Difference test
at α = 0.05.
RESULTS AND DISCUSSION
Hemp sesbania, eclipta, Pennsylvania smartweed, and pitted morningglory were
present at APBF. At ABPF the low rate of RicePyr LC® was not as effective at 4 WAT
as the standard treatment for control of pitted morningglory, eclipta, and hemp sesbania
(Table 1). The high rate of RicePyr LC® provided weed control at 4 WAT comparable
to the standard treatment, except for eclipta control was lower than the standard treatment. Control of all weeds with the high rate of RicePyr LC® was >80% at APBF at
4 WAT.
At RREC, hemp sesbania and ivyleaf morningglory were evaluated. Control of
both weeds was comparable between the high rate of RicePyr LC® and the standard
treatment at 4 WAT, with RicePyr LC® providing at least 89% control (Table 1).
Weeds present at PTBS included hemp sesbania, entireleaf morningglory, eclipta,
and Palmer amaranth. Control of all weeds with the highest rate of RicePyr LC® was
comparable to the standard treatment at 4 WAT (Table 1). The high rate of RicePyr
LC® controlled hemp sesbania 89%, entireleaf morningglory 75%, eclipta 68%, and
Palmer amaranth 81% at 4 WAT. No rice injury was observed at any site. In summary,
RicePyr LC® at 3 qt/acre generally provided equivalent weed control to our selected
standard treatment, but weed control with RicePyr LC at 2 qt/acre was often less than
the standard treatment.
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SIGNIFICANCE OF FINDINGS
Price for RicePyr LC® at 3 qt/acre is anticipated to be comparable to SuperWham
at 2 qt/acre plus Grandstand at 0.67 pt/acre in 2009. RicePyr LC® will simplify weed
control on rice levees because propanil and triclopyr, the two active ingredients in RicePyr LC®, will be a premixed product. Although RicePyr LC® at 3 qt/acre did provide
control of a range of broadleaf weeds on levees, it must be noted that applications were
made when weeds were <12-in. tall or <12-in. runners. Applications on larger weeds
will probably result in a lower level of weed control than observed in these trials.
ACKNOWLEDGMENTS
The continued support of weed management research in rice by the Arkansas
Rice Research and Promotion Board is gratefully appreciated. Partial support for this
research was provided by RiceCo.
LITERATURE CITED
Norsworthy, J.K., N.R. Burgos, R.C. Scott, and K.L. Smith. 2007. Consultant perspectives on weed management needs in Arkansas rice. Weed Technol. 21:832839.
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AAES Research Series 571
Table 1. Weed control on rice levees at 4 weeks after
the Arkansas Pine Bluff Research Farm, and the
PTBS
Treatmentz
Rate
Hemp
sesbania
-------------------------------------------------------------------------- RicePyr LC® 2 qt/acre
RicePyr LC® 3 qt/acre
SuperWham + 2 qt/acre +
Grandstand
0.67 pt/acre
LSD (0.05)
Entireleaf
morningglory
Eclipta
90
61
59
81
89
75
68
81
88
NSy
83
21
69
NS
83
17
All herbicide treatments were applied with crop oil concentrate at 1% v/v.
NS = nonsignificant.
z
y
188
Palmer
amaranth
B.R. Wells Rice Research Studies 2008
treatment at the Pine Tree Branch Station (PTBS),
Rice Research and Extension Center (RREC) in 2008.
APBF
Hemp
sesbania
RREC
Pitted
morningglory
Eclipta
Pennsylvania
smartweed
Hemp
sesbania
Ivyleaf
morningglory
------------(% control)---------------------------------------------------------------------------------------------
83
95
92
8
75
83
91
13
74
81
96
10
93
94
91
NS
90
92
91
NS
89
89
92
NS
189