Information from 1999 Missouri Rice Research Update, February 2000.

Summary of Herbicide Evaluations in Rice

Andy Kendig, Anthony Ohmes, Robert Barham, and Paula Ezell

Abstract

Seven studies were conducted in 1999 on two soils, a Crowley silt loam and a Portageville clay. In study one, no crop response (injury) was observed from neither Prowl nor Command. Control generally increased with increasing rates and typically better on silt loam. In study two, Stam + residual (Facet or Command) program on 2- to 3-leaf barnyardgrass provided similar control. Optimal control from Stam + Facet was at the early timing. Command followed by Grandstand or Regiment provided control similar to Stam programs. In study three, Split applications of Liberty generally better than single applications. In study four, Control from PPI and PRE applications of Pursuit were generally inadequate from the targeted use rate of 0.063 lbs ai/A, regardless of soil. POST and sequential applications generally provided more control of both barnyardgrass and red rice. In study five, early applications at the higher rates were necessary for 70% or greater control. In study six, the three graminicides control was generally not influenced by tank mixtures with broadleaf compounds, however, Ricestar and Clincher tank mixed with Permit did have reduced yield. In study seven, Raptor and Lightning split applications provided greater than 90% control of barnyardgrass.

Introduction

Rice weed control is one area of weed science where several new experimental compounds, such as Clincher as well as products that are already established in other crops, such as Command are being tested. Rice weed control is challenging due to the fact that there are fewer compounds available compared to other crops. The primary yield robbing weeds are grass species. One grass species that is a particular challenge is red rice. Another area that is being developed to help reduce red rice problems is herbicide tolerant rice. Seven research studies were conducted in 1999 to evaluated weed control of both individual herbicides and herbicide programs.

The objectives of study one were to evaluate crop response and weed control of preemergence (PRE) herbicides, primarily Prowl and Command. The objectives of study two were to evaluated various weed control programs. The objectives of study three were to evaluate weed control, in particular red rice control, and various programs in Liberty Link rice using Liberty herbicide. The objectives of study four were to evaluate barnyardgrass and red rice control with Pursuit on Pursuit-resistant rice. The objectives of study five were to evaluate barnyardgrass control with three experimental graminicides, Ricestar (Whip 360 + safener), Clincher and Aura. The objective of study six was to investigate any possible antagonism when Ricestar, Clincher or Aura were tank mixed with broadleaf compounds. The objective of study seven was to evaluate possible alternatives to Pursuit on Pursuit-resistant rice.

Materials and Methods

The seven studies were conducted on two soils, a Crowley silt loam located at the Missouri Rice Farm and a Portageville clay located at the UMC Lee Farm. Four of the seven studies were conducted at both locations in order to compare herbicide performance on the different soil types. The studies were initiated in May using standard weed science research methods. Three rice varieties were planted, Jefferson, Liberty Link, and IMI tolerant at both locations. Jefferson was used for all the conventional weed control evaluations. Visual weed control ratings were taken through the growing season. Yield was taken at the silt loam location. The seven studies conducted in 1999 will be summarized in individual sections based on the objectives of that study.

Study 1. Study one was conducted on both soil types. There were 23 herbicide treatments and an untreated check. The primary treatments included Prowl and Command applied pre-plant incorporated (PPI) (Command only), PRE and delayed PRE (DPRE). Prowl rates for both the PRE and DPRE timings were 1, 1.5, 2 lbs ai/A. Command rates for PRE and DPRE were 0.4, 0.8, 1.6 lbs ai/A, additional rates included 0.1 (PRE only), 0.2 (PRE only), 0.3 (DPRE only) lbs ai/A. Additional treatments included: a split application of Prowl; PRE and DPRE applications of Facet at 0.375 lbs ai/A; DPRE application of a tank mix of Bolero (1 lb) + Command (0.1 lb) + Facet (0.1 lb) + Prowl (0.25 lb) ai/A; and Command tank mixed with Facet or Bolero.

Study 2. Study two was conducted on both soil types. In one set of programs, a Stam at 3 lbs + Facet at 0.25 lbs tank mix was evaluated for control of 2-3-lf, 4-5-lf, 6-8-lf, and 10-14-lf barnyardgrass. Other Stam programs included Stam tank mixes with Prowl, Command or Facet and sequential Stam and Arrosolo applications. Stam and Arrosolo at 3 lbs ai/A, Prowl at 1 lb ai/A, Command at 0.5 lbs ai/A, and a reduced rate of Facet (0.125 lbs) were applied to control 2-3-lf grass. In another set of programs, Prowl and Command were applied DPRE and PRE, respectively. Prowl and Command rates remained the same as in program two. They were followed by (fb) a preflood application of Grandstand at 0.25 lbs ai/A or Regiment at 0.0198 lbs ai/A. In addition to the programs PRE and Postflood applications of Facet were included.

Study 3. The third study was conducted on both soil types. Treatments included: 1) Liberty alone at 0.36 lb ai/A applied at 2-3-leaf, preflood and postflood; 2) Sequential Liberty at 0.31 lb ai/A applied at 2-3-leaf fb preflood or postflood applications, preflood fb postflood; 3) Three applications of Liberty at 2-3-leaf fb preflood fb postflood.

Study 4. Study 4 was also conducted on both soil types. Treatments included; 1) PPI, PRE, and early POST applications of Pursuit at 0.063, 0.094, and 0.125 lbs ai/A and 2) PPI, PRE or early POST fb early POST or preflood sequential applications. Rice was not flushed after planting and small rainfalls occurred within 5 days of planting.

Study 5. Study five was conducted on a Portageville clay. The treatments were 0.12 and 0.16 lbs ai/A of Ricestar, 0.125 and 0.188 lb ai/A of Clincher, and 0.067 and 0.094 lbs ai/A of Aura rates applied to 2- to 3-leaf, 4- to 5-leaf, 6- to 8-leaf (preflood), and 10- to 14-leaf (postflood) barnyardgrass in rice.

Study 6. Study six was conducted on a Crowley silt loam. The treatments were Ricestar at 0.16 lbs ai/A, Clincher at 0.188 lbs ai/A, and Aura at 0.094 lbs ai/A applied alone and in tank mixtures with Basagran, Blazer, Grandstand, Londax, Permit, Aim, and Stam on 4- to 5-leaf barnyardgrass.

Study 7. Study seven was on conducted on a Crowley silt loam. The alternatives were Scepter, PRE at 0.125 lbs ai/A and split applications of Raptor (0.04 lbs), Lightning (0.056 lbs), Accent (0.031 lbs), Matrix (0.0234 lbs), and Staple (0.063 lbs).

Results and Discussion

Study 1. No injury was observed on either soil type. Prowl and Command were weaker on the clay soil, possibly due to higher sorption of compounds. The high rates of Prowl (DPRE) and Command (PRE) provided 70 to 85% barnyardgrass control 6-7 weeks after application. The lower rates provided less than 60% control. Prowl applied PRE at all three rates provided less control of barnyardgrass than the 1 lb rate, DPRE on the clay. Prowl and Command on the silt loam provided higher control of barnyardgrass at all rates compared to the clay. Prowl at all three rates provided 70 to 80% control. Prowl applied DPRE was slightly better than PRE on the silt loam as well. Command applied PPI and PRE at 0.4, 0.8, 1.6 lbs ai/A provided 90% or greater barnyardgrass control on the silt loam. Prowl and Command were similar to Facet and the additional treatments were generally similar to the Command and Prowl treatments, also.

Yields in general were low for all treatments. Yield from the Prowl and Command treatments increased from 37 and 27 bu/A to 78 and 76 bu/A, respectively, with increasing rates. Yields that did stand out were the split application of Prowl and PRE and DPRE Facet treatments which yielded over 110 bu/A.

Study 2. Stam + Facet provided 88% control of 4-5-lf barnyardgrass on the clay, while other timings provided 70% or less control. All timings provided 100% control of hemp sesbania. Stam + Facet provided 93% control of 2-3-lf barnyardgrass on the silt loam, while other timings provided less than 70% control. Stam + Command provided 90% control of 2-3-lf barnyardgrass on the clay, which was equivalent to sequential Arrosolo applications. However, Stam + Prowl and sequential Stam poorly control barnyardgrass. The sequential programs provided 95 and 100% control of hemp sesbania. Both Stam + residual and sequential programs provided 80% or greater control of barnyardgrass in the silt loam. Stam + the reduced rate of Facet provided control equal to the higher Facet rate at the same timing. Prowl followed by(fb) Grandstand on both the clay and silt loam provided less than 50% control of barnyardgrass. Prowl fb Regiment on the silt loam only provided 70% control of barnyardgrass. The other programs which included Command fb Grandstand or Regiment and Prowl fb Regiment (loam only) provided greater than 80% control of barnyardgrass. Both Grandstand and Regiment provided excellent control of hemp sesbania. Facet applied PRE provided 50 and 80% control of barnyardgrass on the clay and silt loam, respectively. Facet applied postflood provided 50 and 15% on the clay and silt loam, respectively. No crop injury was observed.

Stam + Facet applied at the 2-3-leaf timing yielded 155 bu/A and decreased with later timings. Stam + Prowl or Command yielded similar to the 2-3-leaf Stam + Facet application. The three Stam + residual programs yielded more than 20 bu/A higher than split applications of Stam and Arrosolo. Prowl or Command + Grandstand or Regiment generally yielded the same. Facet, alone, PRE yielded similar to the split applications of Stam and Arrosolo and to the Prowl or Command + Grandstand or Regiment programs.

Study 3. Liberty alone at any application timing on both soils was weak on barnyardgrass and red rice, with control for the most part 80% or lower. Sequential applications provided between 80 and 90% control of both barnyardgrass and red rice with the exception of the 2-3-leaf fb postflood program which was less than 20%. Three applications were the same as two applications. No crop injury was observed.

Study 4. On the clay, barnyardgrass control from incorporated Pursuit increased from 8 up to 39% as the rate was increased from 0.063 to 0.125 lbs ai/A. On the silt loam, barnyardgrass and red rice control increased from 55 to 83% and 35 to 85% as the rate was increased from 0.063 to 0.125 lb ai/A. With similar PRE applications, barnyardgrass control on the clay increased from 14% at 0.063 lb ai/A to 30% at 0.125 lbs ai/A and on the silt loam increased from 28% at 0.063 lb ai/A to 70% at 0.125 lbs ai/A. Higher herbicide sorption likely decreased control on the clay relative to the silt loam. However, control was generally inadequate from the targeted use rate of 0.063 lbs ai/A, regardless of soil. POST applications at the 2-3-leaf barnyardgrass stage at any of the tested rates provided 83% or greater barnyardgrass and 75% or greater red rice control on the silt loam. On the clay, 0.125 and 0.094 lbs ai/A provided greater than 80% barnyardgrass control. Sequential applications were generally similar to single POST applications. No crop injury was observed.

Study 5. Ricestar provided 79 and 86% control of 2- to 3-leaf and 4- to 5-leaf barnyardgrass at the 0.12 and 0.16 lbs ai/A rates, respectively. Ricestar provided 70% or less control of 6- to 8-leaf and 10- to 14-leaf barnyardgrass at both rates. Ricestar averaged 5 to 20% weaker than Whip 360 at respective rates and timings. At 0.125 lbs ai/A, Clincher provided 60% control of 2- to 3-leaf barnyardgrass, while all other timings were less. At 0.188 lbs ai/A, Clincher provided 69% control of 2- to 3-leaf barnyardgrass and lower control at later timings. Aura, at 0.067 lbs ai/A, provided poor (<60%) barnyardgrass control at all four timings. At 0.094 lbs ai/A control was 70% for 2- to 3-leaf and 4- to 5-leaf barnyardgrass and decreased at later timings.

Study 6. Ricestar alone provided 80% control of barnyardgrass while control was 40% or less with Permit or Aim tank mixtures. Other mixtures provided control similar to Ricestar alone. Clincher alone provided 50% control of barnyardgrass while control was 70 to 85% with Blazer, Grandstand, Aim, and Stam tank mixtures. However, statistically all mixtures provided control similar to Clincher alone. Aura alone provided 28% control of barnyardgrass while control was 70% with Grandstand. All other mixtures were similar Aura alone.

In general yields reflected weed control ratings. There was a yield reduction with the Ricestar and Clincher + Permit treatments. Yields were generally similar among the Aura treatments with exception of Aura + Blazer which yielded higher than other treatments.

Study 7. Scepter, Matrix and Staple provided less than 80% control of barnyardgrass and red rice. Split applications of Raptor and Lightning provided greater than 90% control of both grasses. Accent provided approximately 80% control of both grasses.

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