WEED RESEARCH IN RICE - LOUISIANA STATE UNIVERSITY

Goals / Objectives
EVALUATE HERBICIDES FOR WEED CONTROL AND RICE TOLERANCE UNDER DRILL-SEEDED AND WATER-SEEDED CULTURE AND THEIR IMPACT ON THE ENVIRONMENT, AND TO ESTABLISH WEED CONTROL PROGRAMS FOR HERBICIDE-RESISTANT RICE LINES FOR LOUISIANA. RESEARCH WILL ALSO EVALUATE EXISTING AND NEW TECHNOLOGIES FOR SHORT AND LONG TERM RED RICE CONTROL IN RICE PRODUCTION. PERSISTENCE OF SOIL APPLIED RICE HERBICIDES WILL ALSO BE EVALUATED FOR CARRYOVER POTENTIAL.

Project Methods
AS NEW HERBICIDES ARE DEVELOPED BY THE AGRICHEMICAL INDUSTRY THEY WILL BE EVALUATED FOR THE EFFECTIVENESS IN CONTROLLING OR SUPPRESSING WEEDS IN WATER-SEEDED AND DRILL-SEEDED RICE. TEST SITES AT THE RICE RESEARCH STATION, WHICH ARE INFESTED WITH MAJOR RICE WEEDS, WILL BE UTILIZED. AS NEW HERBICIDE-RESISTANT RICE CULTIVARS ARE DEVELOPED RESEARCH WILL BE CONDUCTED TO DEVELOP WEED CONTROL PROGRAMS THAT WILL BEST FIT THESE NEW CULTIVARS. RESEARCH WILL BE CONDUCTED THAT DETERMINES THE BEST APPLICATION TIMINGS, RATES, AND POTENTIAL TANK-MIXES FOR MAXIMUM WEED CONTROL WITH THE HERBICIDE-RESISTANT CULTIVARS. THIS PROJECT WILL EVALUATE CURRENT AND NEW TECHNOLOGIES FOR RED RICE MANAGEMENT IN CONTINUOUS RICE CULTURE AND RICE/SOYBEAN/RICE ROTATIONS. CARRYOVER POTENTIAL OF RICE HERBICIDES TO RICE AND OTHER ROTATIONAL CROPS WILL BE EVALUATED. IMAZETHAPYR IS THE TARGET HERBICIDE FOR USE IN THE NEW IMIDAZOLINONE-RESISTANT RICE AND IT HAS THE POTENTIAL TO CARRYOVER TO ROTATIONAL CROPS. IMAZETHAPYR HAS A HALF-LIFE IN SOIL OF 60 TO 90 DAYS, AND CERTAIN ROTATIONAL CROPS MAY HAVE RESTRICTIONS FROM A RECROPPING STANDPOINT. RICE HAS A 40-MONTH RECROPPING RESTRICTION AFTER AN APPLICATION OF IMAZETHAPYR TO A LABELED CROP. IT WILL BE IMPORTANT TO DETERMINE IF A CONVENTIONAL RICE CULTIVAR CAN BE PLANTED AS A ROTATIONAL CROP FOLLOWING AN APPLICATION OF IMAZETHAPYR TO IMIDAZOLINONE RESISTANT RICE.

Progress 05/01/99 to 04/30/04

Outputs
Research was established to evaluate imidazolinone-tolerant rice lines. A field study was conducted at the Rice Research Station to evaluate weed control and water management strategies for drill-seeded Clearfield rice CL-161 variety. Four water management strategies included: a single surface irrigation at planting, surface irrigation as needed prior to permanent flood, maintain saturated prior to permanent flood, and early permanent flood establishment on one- to two-leaf rice. Permanent flood on the first three strategies was established on four- to five-leaf rice. Herbicides treatments consisted of 70 g ai/ha imazethapyr preemergence (PRE) followed by (fb) 70 g/ha imazethapyr mid-postemergence (MPOST) on three- to four-leaf rice or a total POST program of 70 g/ha imazethapyr early-POST (EPOST) on two- to three-leaf rice fb 70 g/ha imazethapyr late-POST (LPOST) on four- to five-leaf rice. At 21 and 49 d after LPOST, control decreased for red rice and barnyardgrass within the surface irrigation at planting and the early permanent flood water-management strategies for the PRE fb MPOST program compared with the total POST program. This research indicates that weed control and rice yield can be increased when soil moisture is maintained under saturated conditions in an imidazolinone-tolerant rice production system. In another study, research focused on broadleaf, grass, and nutsedge control using a single post-flood application of the grass herbicide cyhalofop plus an herbicide with broadleaf activity. Cyhalofop was applied alone at 0.31 kg ai/ha or mixed with 0.03 kg/ha V-10029, 0.04 kg/ha bensulfuron, 0.43 kg/ha triclopyr, 0.28 kg/ha acifluorfen, and 0.28 kg/ha triclopyr plus 1.1 kg/ha propanil. A propanil plus quinclorac mixture at 4.5 and 0.43 kg/ha, respectively, was added for comparison. At 35 days after application, cyhalofop alone, plus bensulfuron or aciflurofen controlled barnyardgrass and Amazon sprangletop 83 to 94%. Cyhalofop plus V-10029 controlled barnyardgrass and Amazon sprangletop 93 and 51%, respectively. Cyhalofop plus V-10029, bensulfuron, or triclopyr plus propanil controlled rice flatsedge 88%, which was comparable with the comparison propanil plus quinclorac. At 49 days after application, cyhalofop alone or mixed with bensulfuron controlled barnyardgrass and Amazon sprangletop 97 to 98%. Cyhalofop plus bensulfuron controlled rice flatsedge 96%, which was comparable to propanil plus quinclorac. Rice grain yields were 5220 to 7370 kg ha-1 with cyhalofop plus all broadleaf herbicide mixes. A study was conducted to evaluate the competitiveness of four currently grown rice lines with red rice in water-seeded production. CL 121, Cocodrie, Drew, and Jasmine were chosen based on different growth habits, days to maturity, and plant height. The tall late maturing, high tillering Jasmine reduced red rice parameters more than the other cultivars.

Impacts
Producers will be able to control red rice and other difficult to control weeds by using imazethapyr herbicide on inidazoline-tolerant rice lines. This technology will increase the amount of profit for producers by decreasing yield losses due to weed competition and reduced dockage due to red rice grains in the harvested crop. The ability to apply cyhalofop with a broadleaf herbicide will allow producers to control both grass and broadleaf weeds with one application. This will reduce the total number of herbicide applications, which in turn reduces time, fuel and water usage, and overall herbicide use will ultimately decline; therefore, allowing producers to be more profitable by decreasing overall inputs, and reducing fixed and variable cost.

Publications

Mudge, C. R., E. P. Webster, W. Zhang and C. T. Leon. 2003. Varietal tolerance to Command in water-seeded rice. Proc. South. Weed Sci. Soc. 56:40.
Pellerin, K. J., E. P. Webster, W. Zhang, and D. C. Blouin. 2003. Herbicide mixtures in water-seeded imidazolinone-resistant rice (Oryza sativa). Weed Technol. 17:836-841.
Tindall, K. V., B. J. Williams, E. P. Webster, and M. J. Stout. 2003. Effects of barnyardgrass density on rice yields. Proc. South. Weed Sci. Soc. 56:306.
Webster, E. P. 2003. Changes in water-seeded rice weed management. Proc. South. Weed Sci. Soc. 56:364.
Webster, E. P., D. Y. Lanclos, and W. Zhang. 2003. Influence of glufosinate on glufosinate-resistant rice (Oryza sativa) on seed weight, seed germination, and seedling vigor. Weed Technol. 17:51:54.
Webster, E. P., C. T. Leon, and W. Zhang. 2003. Weed control and water-management strategies for herbicide-tolerant rice. Weed Sci. Soc. Am. Abstr. 43:39.
Williams, B. J. and E. P. Webster. 2003. Response of annual weeds and Clearfield rice to imazethapyr in broadcast dry-seeded systems. Weed Sci. Soc. Am. Abstr. 43:40.
Zhang, W., E. P. Webster, and D. Y. Lanclos. 2003. Critical period for weed control in glufosinate-resistant rice (Oryza sativa). Proc. Louis. Plant Protect. Assoc. 12:61.
Zhang, W., E. P. Webster, D. Y. Lanclos, and J. P. Geaghan. 2003. Effect of weed interference and weed free duration on glufosinate-resistant rice (Oryza sativa). Weed Technol. 17:876-880.
Zhang, W., E. P. Webster, Leon, C. T. and C. R. Mudge. 2003. Differential response of rice varieties to Command. Proc. South. Weed Sci. Soc. 56:39.
Bryant, K. D., R. L. Nichols, C. T. Allen, N. R. Benson, F. M. Bourland, L. D. Earnest, M. S. Kharboutli, K. L. Smith, and E. P. Webster. 2003. Transgenic cotton cultivars: An economic comparison in Arkansas. J. Cotton Sci. 7:194-204 [Online]. Available at http://journal.cotton.org/2003/issue04/pdf/jcs03i4-7.pdf.
Ellis, J. M., J. L. Griffin, S. D. Linscombe, E. P. Webster. 2003. Rice (Oryza sativa) and corn (Zea mays) response to simulated drift of glyphosate and glufosinate. Weed Technol. 17:452-460.
Dunand, R. T., E. P. Webster, and S. D. Linscombe. 2003. Red rice growth suppression in Clearfield and Liberty Link rice. Proc. South. Weed Sci. Soc. 56:46.
Griffin, R. M., E. P. Webster, W. Zhang, C. T. Leon, and C. R. Mudge. 2003. Tolerance of rice varieties to Command in a drill-seeded system. Proc. Louis. Plant Protect. Assoc. 12:60.
Lanclos, D. Y., E. P. Webster, W. Zhang, and S. D. Linscombe. 2003. Response of glufosinate-resistant rice (Oryza sativa) to glufosinate application timings. Weed Technol. 17:157:160.
Leon, C. T., E. P. Webster, and W. Zhang. 2003. Post-flood cyhalofop tank-mixtures for rice weed control. Weed Sci. Soc. Am. Abstr. 43:2.
Leon, C. T., E. P. Webster, and W. Zhang. 2003. Post-flood rice weed control options. Proc. Louis. Plant Protect. Assoc. 12:58.
Mudge, C. R., E. P. Webster, W. Zhang and C. T. Leon. 2003. Potential safeners for Command in water-seeded rice. Proc. South. Weed Sci. Soc. 56:302.
Leon, C. T., E. P. Webster, W. Zhang and C. R. Mudge. 2003. Aim programs for drill seeded rice (Oryza sativa). Proc. South. Weed Sci. Soc. 56:54.
Mudge, C. R., E. P. Webster, W. Zhang and C. T. Leon. 2003. Evaluation of Command impregnated on fertilizer in water-seeded rice. Proc. Louis. Plant Protect. Assoc. 12:43.
Zhang, W., E. P. Webster, and D. C. Blouin. 2003. Effect of clomazone rates and timings on rice (Oryza sativa) and barnyardgrass (Echinochloa crus-galli). Weed Sci. Soc. Am. Abstr. 43:39.

Progress 01/01/02 to 12/31/02

Outputs
In 2002, research was established to evaluate imidazolinone-tolerant rice lines. A field study was conducted at the Rice Research Station to evaluate weed control and water management strategies for drill-seeded Clearfield rice. Four water management strategies included: a single surface irrigation at planting, surface irrigation as needed prior to permanent flood, maintain saturated prior to permanent flood, and early permanent flood establishment on one- to two-leaf rice. Permanent flood on the first three strategies was established on four- to five-leaf rice. Herbicides treatments consisted of `CL-161' rice treated with 70 g ai/ha imazethapyr preemergence (PRE) followed by (fb) 70 g/ha imazethapyr mid-postemergence (MPOST) on three- to four-leaf rice or a total POST program of 70 g/ha imazethapyr early-POST (EPOST) on two- to three-leaf rice fb 70 g/ha imazethapyr late-POST (LPOST) on four- to five-leaf rice. At 21 and 49 d after LPOST, control decreased for red rice and barnyardgrass within the surface irrigation at planting and the early permanent flood water-management strategies for the PRE fb MPOST program compared with the total POST program. However, control decreased for Amazon sprangletop for the total POST program compared with PRE fb MPOST program. Rice treated with imazethapyr in a total POST program under the saturated water-management strategy resulted in a higher yield compared with the PRE fb MPOST program in the other water management strategies. However, no difference was observed within the saturated water-management strategy. This research indicates that weed control and rice yield can be increased when soil moisture is maintained under saturated conditions in an imidazolinone-tolerant rice production system. In another study, research focused on broadleaf, grass, and nutsedge control using a single post-flood application of the grass herbicide cyhalofop plus an herbicide with broadleaf activity. Cyhalofop was applied alone at 0.31 kg ai/ha or mixed with 0.03 kg/ha V-10029, 0.04 kg/ha bensulfuron, 0.43 kg/ha triclopyr, 0.28 kg/ha acifluorfen, and 0.28 kg/ha triclopyr plus 1.1 kg/ha propanil. A propanil plus quinclorac mixture at 4.5 and 0.43 kg/ha, respectively, was added for comparison. At 35 days after application, cyhalofop alone or plus triclopyr or bensulfuron controlled barnyardgrass, Amazon sprangletop, and broadleaf signalgrass more than 82%. Cyhalofop plus V-10029 controlled barnyardgrass, Amazon sprangletop, and broadleaf signalgrass 91, 74, and 97%, respectively. Cyhalofop plus V-10029, bensulfuron, or triclopyr plus propanil generally controlled rice flatsedge and yellow nutsedge more than 75%, which was comparable to the comparison propanil plus quinclorac. Cyhalofop plus any herbicide controlled hemp sesbania at least 96%. At 49 days after application, cyhalofop alone or mixed with bensulfuron controlled barnyardgrass, Amazon sprangletop, and broadleaf signalgrass 93 to 96%. Cyhalofop plus bensulfuron controlled rice flatsedge, yellow nutsedge, and hemp sesbania 90 to 95%, which was comparable to propanil plus quinclorac. Rice grain yields were 4704 to 7100 kg/ha.

Impacts
Producers will be able to control red rice and other difficult to control weeds while producing a crop of rice with the herbicide imazethapyr. This technology will increase the amount of profit for producers by decreasing yield losses due to weed competition and reduced dockage due to the lack of red rice grains in the harvested crop. The ability to apply cyhalofop with a broadleaf herbicide will allow producers to control both grass and broadleaf weeds with one application. This will reduce the total number of herbicide applications, which in turn reduces time, fuel and water usage is reduced, and overall herbicide use will ultimately decline; therefore, allowing producers to be more profitable by decreasing overall inputs, and reducing fixed and variable cost.

Publications

Levy, R. J., Jr., E. P. Webster, and S. D. Linscombe. 2002. Impact of cultural practices on imazethapyr in LA rice production. Proc. South. Weed Sci. Soc. 55:18.
Pellerin, K. J., E. P. Webster, C. T. Leon, and W. Zhang. 2002. NewPath combinations in water-seeded rice. Proc. Louis. Plant Protect. Assoc. 12:42.
Pellerin, K. J., E. P. Webster, C. T. Leon, and W. Zhang. 2002. Potential of imidazolinone-tolerant rice and imazethapyr under different rice seeding methods. Rice Tech. Wrkg. Grp. 29:169.
Pellerin, K. J., E. P. Webster, W. Zhang, and C. T. Leon. 2002. Imazethapyr programs in water-seeded-rice. Proc. South. Weed Soc. 55:17.
Shaw, D. R., A. Rankins, M. W. Shankle, S. M. Schraer, C. A. Smith, G. P. Murphy, C. H. Tingle, T. A. Baughman, and E. P. Webster. 2002. Benefits of buffer strips for protection of surface water. Weed Sci. Soc. Am. Abstr. 42:90
Tindall, K. V., E. P. Webster, and M. J. Stout. 2002. Potential impact of Liberty-Link rice on rice water-weevil. Proc. South. Weed Sci. 55:117.
Webster, E. P., C. T. Leon, W. Zhang, and K. J. Pellerin. 2002. Herbicide options in water-seeded rice. Rice Tech. Wrkg. Grp. 29:165.
Webster, E. P., C. T. Leon, W. Zhang, and K. J. Pellerin. 2002. Command use in water-seeded rice. Proc. South. Weed Sci. Soc. 55:37.
Webster, E. P., K. J. Pellerin, C. T. Leon, and W. Zhang. 2002. Herbicide programs in imidazolinone-tolerant rice (Oryza sativa). Weed Sci. Soc. Am. Abstr. 42:35.
Williams, B. J. and E. P. Webster. 2002. Evaluation of systems for broadcast dry-seeding Clearfield rice. Rice Tech. Wrkg. Grp. 29:159.
Zhang, W. and E. P. Webster. 2002. Shoot and Root Growth of Rice (Oryza sativa) in Response to Bispyribac-sodium. Weed Technol. 16:768-772.
Dunand, R. T., E. P. Webster, and S. D. Linscombe. 2002. Gibberellic acid and crop injury in Clearfield rice. Proc. South. Weed Sci. Soc. 55:117.
Guice, J. B., P. H. Bruno, A. M. Harden, J. S. Harden, S. D. Linscombe, E. P. Webster, and B. J. Williams. 2002. Weed control and crop tolerance in a water-seeded Clearfield rice production system. Rice Tech. Wrkg. Grp.29:169.
Lanclos, D. Y., E. P. Webster, and W. Zhang. 2002. Glufosinate tank-mix combinations in glufosinate-resistant rice (Oryza sativa). Weed Technol. 16:659:663.
Langston, V. B., R. B. Lassiter, D. M. Simpson, R. K. Mann, F. L. Baldwin, J. A. Kendig, A. Klosterboer, M. E. Kurtz, K. Smith, R. E. Strahan, R. E. Talbert, E. P. Webster, and B. J. Williams. 2002. Grass control with post-flood applications of cyhalofop-butyl in dry seeded rice. Proc. South. Weed Sci. Soc. 55:213
Zhang, W., E. P. Webster, and M. P. Braverman. 2002. Influence of rice (Oryza sativa) herbicides on carryover of rotational crop herbicides to rice. Weed Technol. 16:340-345.
Zhang, W., E. P. Webster, C. T. Leon, and K. J. Pellerin. 2002. Bispyribac-sodium applications on shoot and root growth of rice (Oryza sativa). Weed Sci. Soc. Am Abstr. 42:36.
Zhang, W., E. P. Webster, C. T. Leon, and K. J. Pellerin. 2002. Evaluation of Regiment (bispyribac-sodium) for weed control in rice. Rice Tech. Wrkg. Grp. 29:166.
Zhang, W., E. P. Webster, C. T. Leon, K. J. Pellerin, and S. D. Linscombe. 2002. Response of rice varieties to bispyribac-sodium applications. Proc South. Weed Sci. Soc. 55:116.
Zhang, W., E. P. Webster, C. T. Leon, and K. J. Pellerin. 2002. Weed control programs with Regiment. Proc. Louis. Plant Protect. Assn. 12:68.
Leon, C. T., E. P. Webster, K. J. Pellerin, and W. Zhang. 2002. Liberty tank-mixtures for rice weed control. Proc. South. Weed Soc. 55:16.
Leon, C. T., E. P. Webster, W. Zhang, and K. J. Pellerin. 2002. Effect of broadleaf herbicide tank-mixes, application rate, and timing on Ricestar efficacy. Rice Tech. Wrkg. Grp.29:154.
Leon, C. T., E. P. Webster, W. Zhang, and K. J. Pellerin. 2002. Grass control with Ricestar and broadleaf herbicide combinations. Proc. South. Weed Soc. 55:196.
Leon, C. T., E. P. Webster, W. Zhang, and K. J. Pellerin. 2002. Grass control with Ricestar plus broadleaf herbicide tank-mixtures. Proc. Louis. Plant Protect. Assoc. 12:69.
Leon, C. T., E. P. Webster, W. Zhang, and K. J. Pellerin. 2002. Imazethapyr application rates and timings in an imidazolinone-tolerant rice (Oryza sativa L.) system. Weed Sci. Soc. Am. Abstr. 42:35.

Progress 01/01/01 to 12/31/01

Outputs
In 2001, at the Rice Research Station near Crowley LA, research was established to evaluate imidazolinone-tolerant rice lines. Clearfield rice, tolerant to the imidazolinone family of herbicides, was developed at the Rice Research Station and is being evaluated for potential in an overall weed control program. A study was established to determine weed control with imazethapyr at 88 g ai/ha applied preemergence followed by 70 g ai/ha bensulfuron, 0.35 kg ai/ha triclopyr, 5 kg ai/ha propanil plus molinate, 28 g ai/A carfentrazone, 0.84 kg ai/ha acifluorfen plus bentazon, 53 g ai/ha halosulfuron, or 22 g ai/ha bispyribac-sodium tank-mixed with 52 g/ha imazethapyr early postemergence. Results indicate that imazethapyr preemergence followed by propanil plus molinate, bensulfuron, carfentrazone, acifluorfen plus bentazon, or halosulfuron tank-mixed with imazethapyr early postemergence controlled both red rice and other grass and broadleaf weeds above 90% with no reduction in rice yield compared to a standard treatment. In another study research focused on different carriers for clomazone application in water-seeded rice. Clomazone at 0.45 kg ai/ha was applied preplant incorporated (PPI), surface prior to planting (SURFACE), early pegging (EPEG), and late PEG (LPEG) with a CO2-pressurized backpack sprayer set to deliver 140 L/ha. The same rate was impregnated on three different fertilizers and applied at 170 kg/ha at the EPEG and LPEG timings. The three fertilizers used were ammonium sulfate, urea, and a 50:50 blend of ammonium sulfate and urea. EPEG treatments were applied when green leaf tissue had emerged from the seed and the root had begun to extend downward into the soil. The LPEG treatments were applied approximately 5 days later. At 10 d after LPEG (DALPEG), barnyardgrass control was 83 to 95% with all EPEG treatments and 55 to 80% with all LPEG clomazone treatments. Rice flatsedge control was less than 70% for all treatments at 10 DALPEG. Halosufuron at 1.0 oz/A was applied to control rice flatsedge and other escaped broadleaf weeds after the initial rating. At 70 DALPEG, clomazone PPI and LPEG applied with the CO2-pressurized backpack sprayer and an EPEG application of clomazone impregnated on a 50:50 blend of ammonium sulfate and urea fertilizer controlled barnyardgrass 69 to 81%. All other clomazone treatments controlled barnyardgrass 86 to 95% regardless of carrier. Amazon sprangletop control was 95% when treated EPEG with clomazone applied with the CO2-pressurized backpack sprayer at 15 GPA at 70 DALPEG. Control decreased to 70 to 85% with all other EPEG treatments. Delaying initial application to the LPEG timing resulted in Amazon sprangletop control of 54 to 80%. At 10 DALPEG, all EPEG applications of clomazone impregnated on fertilizer injured rice 13 to 21%, and rice treated LPEG was injured 20 to 26%. Rice yield reflected the reduced barnyardgrass control with clomazone applied with a CO2-pressurized backpack sprayer at the PPI and LPEG timings. Rice yield increased when treated with clomazone impregnated on ammonium sulfate or the 50:50 blend applied EPEG and LPEG.

Impacts
For the first time, rice producers will be able to control red rice while producing rice with the herbicide imazethapyr. The use of clomazone in water-seeded rice will allow the control of grass weeds at a reduced cost. Both of these technologies will make rice production more profitable for producers in Louisiana.

Publications

Baughman, T. A., Shaw, D. R., Webster, E. P., and Boyette, M. 2001. Effect of cotton tillage systems on the off-site movement of fluometuron, norflurazon, and sediment in runoff. Weed Technol. 15:186-189.
Dunand, R. T., Webster, E. P., Linscombe, S. D., and Masson, J. A. 2001. Impact of gibberellic acid on crop tolerance of imidazolinone tolerant rice. Proc. South. Weed Sci. Soc. 54:44.
Ellis, J. M., Griffin, J. L., Jones, C. A., Webster, E. P., and Godley, J. L. 2001. Effect of carrier volume on crop response to simulated drift of glyphosate and glufosinate. Proc. South. Weed Sci. Soc. 54:150.
Ellis, J. M., Griffin, J. L., Webster, E. P., and Godley, J. L. 2001. Crop response to simulated drift of glyphosate and glufosinate using constant and proportional spray volumes. Weed Sci. Soc. Am. Abstr. 41:44.
Lanclos, D.Y., Webster, E. P., Griffin, J. L., and Ellis, J. M. 2001. Response of glufosinate-resistant rice to glufosinate in Louisiana. Weed Sci. Soc. Am. Abstr. 41:44.
Lanclos, D. Y., Webster, E. P., and Pellerin, K. J. 2001. Response of Liberty-Link rice to glufosinate application timings. Proc. South. Weed Sci. Soc.54:12.
Levy, R. J., Jr., Webster, E. P., and Linscombe, S. D. 2001. Integrating imidazolinone-tolerant rice in Louisiana production practices. Proc. South. Weed Sci. Soc. 54:166.
Masson, J. A. and Webster, E. P. 2001. Use of imazethapyr in water-seeded imidazolinone-tolerant rice (Oryza sativa). Weed Technol. 15:103-106.
Masson, J. A., Webster, E. P., and Williams, B. J. 2001. Flood depth, application timing, and imazethapyr activity in imidazolinone-tolerant rice (Oryza sativa). Weed Technol. 15:315-319.
Oliver, L. R., Teem, D. H., Walker, R. H., Shaw, D. R., and Webster, E. P. 2001. A 20-year overview of southern weed contest. Proc. South. Weed Sci. Soc.54:22-30.
Pellerin, K. J., Webster, E. P., and Lanclos, D. Y. 2001. NewPath applied alone or in combination with other rice herbicides. Proc. South. Weed Sci. Soc.54:42.
Pellerin, K. J., Webster, E. P., and Masson, J. A. 2001. Broadspectrum weed control with NewPath combinations in rice. Proc. South. Weed Sci. Soc.54:181.
Webster, E. P. and Masson, J. A. 2001. ALS-inhibiting herbicides on imidazolinone-tolerant rice (Oryza sativa). Weed Sci. 49:652-657.
Zhang, W., Webster, E. P., and Selim, H. M. 2001. Efficacy of imazethapyr as affected by soil moisture content. Weed Technol. 15:355-359.

Progress 01/01/00 to 12/31/00

Outputs
In 2000, at the Rice Research Station near Crowley LA, research was established to evaluate herbicide resistant/tolerant rice lines. Clearfield rice, tolerant to the imidazolinone family of herbicides, was developed at the Rice Research Station and is being evaluated for potential in an overall weed control program. A study was established to determine weed control with imazethapyr at 88 g ai/ha applied preplant incorporated or preemergence followed by 70 g ai/ha bensulfuron, 0.35 kg ai/ha triclopyr, 5 kg ai/ha propanil plus molinate, 28 g ai/A carfentrazone, 0.84 kg ai/ha acifluorfen plus bentazon, 53 g ai/ha halosulfuron, or 22 g ai/ha bis-pyribac sodium early postemergence followed by 52 g/ha imazethapyr late postemergence. Results indicate that imazethapyr preplant incorporated or preemergence followed by propanil plus molinate or bis-pyribac sodium early postemergence followed by imazethapyr late postemergence controlled both grass and broadleaf weeds above 90% with no reduction in rice yield compared to a standard treatment. Liberty-Link rice, resistant to the herbicide glufosinate, also has been evaluated in rice production systems. Glufosinate is a non-selective herbicide used primarily for non-crop areas, and it has activity on most weeds commonly present in rice fields including red rice. Transformed glufosinate-resistant Cypress and Bengal rice lines were treated with single applications of 0.84 kg ai/ha glufosinate at seven-day intervals throughout the growing season to evaluate rice tolerance at different growth stages. Transformed Cypress and Bengal treated at 2, 7, 14, 49, and 56 days after emergence (DAE) had increased injury compared with the nontreated. The same lines treated at 21, 28, 35, and 42 DAE had little to no injury. Yield from the Bengal line decreased with the 56 DAE application treatment. Seed were collected after harvest from each treatment and 100 count seed weights, percent germination at 5, 13, 19, 22, and 25 C, and seedling vigor were determined on the collected seed. Results indicate no difference was observed on any of these parameters evaluated. Studies also were conducted on evaluating herbicides for control of grass weeds in rice. Fenoxyprop plus safener, cyhalofop, and BAS-625 were evaluated at three rates and three application timings. The application timings were early postemergence, mid-postemergence, and late postemergence. Results indicate fenoxyprop applied early postemergence or mid-postemergence controlled barnyardgrass, broadleaf signalgrass, and Amazon sprangletop 80 to 90%. Cyhalofop and BAS-625 must be applied early postemergence in order to obtain acceptable control of grass weeds. This research will help producers choose weed control programs that could greatly reduce their herbicide inputs on production rice in Louisiana and directly reduce the amount of herbicides applied to production rice fields.

Impacts
These technologies will affect all aspects of rice production. Rice producers will have more flexibility to integrate more productive, economical, and environmentally positive practices. Weed control cost, number of herbicide applications, and amount of active ingredient will be reduced in production rice.

Publications

McClelland, M. R., J. L. Barrentine, K. J. Bryant, and E. P. Webster. 2000. Roundup Ready cotton in conservation tillage. Proc. South. Weed Sci. Soc. 53:238.
Morris, S. N., E. P. Webster, K. J. Pellerin, and J. A. Masson. 2000. Rice weed control with glyphosate. Proc. South. Weed Sci. Soc. 53:216.
Bollich, P. K., E. P. Webster, M. E. Salassi and G. G. Giesler. 2000. Liberty Link and Arrosolo weed control programs in conventional and stale seedbed rice. Proc. South. Weed Sci. Soc. 53:41.
Lanclos, D. Y., E. P. Webster, and S. N. Morris. 2000. Response of glufosinate-resistant rice to glufosinate. Proc. South. Weed Sci. Soc. 53:231.
Levy, R. J., Jr., E. P. Webster, S. D. Linscombe, and W. Zhang. 2000. Evaluation of cultural practices and imazethpyr application timings in Clearfield rice. Proc. South. Weed Sci. Soc. 53:18.
Masson, J. A., E. P. Webster, S. N. Morris. 2000. Weed control and imidazolinone tolerant rice response to imazethapyr application timings. Proc. South. Weed Sci. Soc. 53:17.
Shaw, D. R., W. H. Morris, E. P. Webster, and D. B. Smith. 2000. Spray volume and droplet size effects on common cocklebur (Xanthium strumarium) control. Weed Technol. 14:321-326.
Viator, B. J., J. L. Griffin, E. P. Webster, J. M. Ellis, and E. P. Richard, Jr. 2000. Potential atrazine resistance in red morningglory and herbicide alternatives in Louisiana sugarcane. Proc. South. Weed Sci. Soc. 53:8.
Webster, E. P, J. A. Masson, and W. Zhang. 2000. Imazethapyr rates and timings in water-seeded rice. Weed Sci. Soc. Am. Abstr. 40:112.
Webster, E. P., D. R. Shaw, T. A. Baughman, C. E. Snipes, and C. T. Bryson. 2000. Influence of cultivation timing on pyrithiobac performance in cotton. Weed Technol. 14:116-121.
Zhang, W. and E. P. Webster. 2000. Activity of imazethapyr on rice weeds at different soil moistures. Proc. South. Weed Sci. Soc. 53:178.
Zhang, W., E. P. Webster, and M. P. Braverman. 2000. Effect of rotational crop herbicides on water- and drill-seeded rice (Oryza sativa). Weed Sci. 6:755-760.
Zhang, W. and E. P. Webster. 2000. Efficacy of imazethapyr applied preplant incorporated or postemergence for rice weed control as affected by soil moisture. Weed Sci. Soc. Am. Abstr. 40:341.

Progress 01/01/99 to 12/31/99

Outputs
Glufosinate-resistant transformed rice lines of Cypress and Bengal were treated with single applications of 0.84 kg/ha glufosinate at 7 day intervals throughout the growing season to evaluate rice tolerance at different growth stages. Little to no injury was observed when the lines were treated at 21 to 42 days after treatment; however, significant injury occurred when treated prior to 21 days after treatment or after 42 days after treatment. Rice yield followed the same trends as injury. A study was conducted to evaluate weed control and crop response with glufosinate at different application timings and flood depths. Glufosinate was applied at the rice stages of 2-3 leaf, 4-5 leaf, and 5-leaf to 1 tiller at 0.42 and 84 kg/ha. Flood depths of 5, 10, and 20 cm were established prior to initial applications. Results indicate rate and flood depth had little effect on red rice control with glufosinate. When heavy weed pressure exists control measures with glufosinate should be accomplished by 2 to 3 weeks after emergence and maintained weed-free for the remainder of the growing season. A weed control study was established to evaluate tank mixtures of glufosinate and other rice herbicides. Results indicate that glufosinate tank-mixed with propanil or propanil plus molinate increased control of barnyardgrass, broadleaf signalgrass, yellow nutsedge, and Indian jointvetch compared with glufosinate alone or other tank-mixes. Data indicates that control was achieved 3-5 days faster with propanil tank-mixes. This research will help producers to determine the best application timing, flood depths, tank-mix partners, and rates of glufosinate in a glufosinate-resistant rice production system to maximize weed control and rice yield. Weed control with imazethapyr was evaluated in a water-seeded system. Imazethapyr was applied at 70, 105, and 140 g ai/ha preplant incorporated, surface application prior to flooding, spraying directly on pre-germinated seed, and at pegging in order to evaluate weed control and imidazolinone-tolerant rice response. Red rice and barnyardgrass control did not differ with any application timing; however, Indian jointvetch control was below 80% for all treatments and evaluation dates. Other herbicides will be needed to control broadleaf weeds in an imidazolinone-tolerant rice production system. Unacceptable rice injury occurred when the imidazolinone-tolerant rice was treated at pegging. A flood depth study was conducted evaluating weed control and crop response with 140 g/ha imazethapyr at different application timings and flood depths with imidazolinone-tolerant rice. Results indicate that flood depth had no effect on weed control or crop injury. However, delaying initial application to 3-4 leaf or 5 leaf to 1 tiller resulted in excessive injury and a reduction in rice yield. Imidazolinone-tolerant rice will change rice production in Louisiana and make it more profitable for the producer. Several other experimental herbicides were evaluated for weed control and crop response. Data indicates that many of these products will be beneficial to the rice producers of Louisiana.

Impacts
This research will benefit the rice producers in Louisiana by allowing them to choose the most profitable weed control program for their needs. Rice weed control programs in the next few years will consist of a broad selection of herbicides with the potential of less active ingredient applied per acre. In conclusion, rice production will be more profitable to producers and consumers as a direct result of this research.

Publications

Webster, E. P., F. L. Baldwin, and T. L. Dillon. 1999. The potential for clomazone use in rice (Oryza Sativa). Weed Technol. 13:390-393.
Webster, E. P., K. J. Bryant, and L. D. Earnest. 1999. Weed control and economics in conventional and glyphosate-tolerant soybean (Glycine max). Weed Technol. 13:586:593.
Baughman, T. A., E. P. Webster, J. W. Sij, Jr., and D. G. Bordovsky. 1999. Effect of postemergence topical applications of Roundup on Roundup cotton yields. Orlando, FL: National Cotton Council. Proc. Beltwide Cotton Conf. p. 731.
Bond, J. A., J. L. Griffin, E. P. Webster, J. M. Ellis, D. A. Peters, and J. L. Godley. 1999. Weed control in IR corn as affected by adjuvant and application timing. Proc. Louis. Plant Protection Assn. 9:26.
Bond, J. A., J. L. Griffin, E. P. Webster, J. M. Ellis, D. A. Peters, and J. L. Godley. 1999. Weed control in IR corn as affected by adjuvant and application timing. Proc. South. Weed Sci. Soc. 52:29.
Ellis, J. M., J. L. Griffin, S. L. Linscombe, E. P. Webster, and J. L. Godley. 1999. Crop response to Roundup Ultra and Liberty simulated drift. Proc. South. Weed Sci. Soc. 52:59.
Ellis, J. M., J. L. Griffin, S. L. Linscombe, E. P. Webster, and J. L. Godley. 1999. Soybean and rice response to Roundup Ultra and Liberty simulated drift. Proc. Louis. Plant Protection Assn. 9:41.
Ellis, J. M., J. L. Griffin, and E. P. Webster. 1999. Corn response to simulated drift of glyphosate and glufosinate. Weed Sci. Soc. Am. Abstr. 39:2.
Ellis, J. M., J. L. Griffin, and E. P. Webster. 1999. Weed control in Roundup Ready soybeans with and without soil applied herbicides. Proc. Louis. Plant Protection Assn. 9:21.
Lanclos, D.Y., E. P. Webster, J. L. Griffin, S. D. Linscombe, and J. A. Masson. 1999. Evaluation of glufosinate applied at intervals on glufosinate-resistant rice. Proc. Louis. Plant Protection Assn. 9:22.
Lanclos, D.Y., E. P. Webster, J. L. Griffin, S. D. Linscombe, and W. Zhang. 1999. Tolerance of glufosinate-resistant rice lines to glufosinate. Weed Sci. Soc. Am. Abstr. 39:11.
Lanclos, D. Y., E. P. Webster, and W. Zhang. 1999. Glufosinate-resistant rice lines treated with glufosinate at intervals throughout the season. Proc. South. Weed Sci. Soc. 52:213.
Masson, J. A., E. P. Webster, and D. Y. Lanclos. 1999. Application timings of imazethapyr in water-seeded culture. Proc. Louis. Plant Protection Assn. 9:33.
Masson, J. A., E. P. Webster, and S. N. Morris. 1999. Rice Response to imazethapyr application timings in water-seeded culture. Proc. South. Weed Sci. Soc. 52:235.
Masson, J. A., E. P. Webster, and S. N. Morris. 1999. Evaluation of imazethapyr on imidazolinone-resistant rice. Proc. South. Weed Sci. Soc. 52:18.
Morris, S. N., E. P. Webster, and D. Y. Lanclos. 1999. Evaluation of Facet DF at different application timings. Proc. South. Weed Sci. Soc. 52:17.
Morris, S. N., E. P. Webster, and W. Zhang. 1999. Application timings for rice herbicides with soil activity. Proc. Louis. Plant Protection Assn. 9:34.
Viator, B. J., J. L. Griffin, E. P. Webster, and E. P. Richard, Jr. 1999. Potential red morningglory (Ipomoea coccinea) resistance to atrazine. Proc. Louis. Plant Protection Assn. 9:225.
Viator, B. J., J. L. Griffin, E. P. Webster, and E. P. Richard, Jr. 1999. Potential red morningglory (Ipomoea coccinea) resistance to atrazine. Proc. South. Weed Sci. Soc. 52:178.
Webster, E. P., J. A. Masson, and W. Zhang. 1999. Imazethapyr application rates and timings in water-seeded rice culture. Weed Sci. Soc. Am. Abst. 39:320.
Webster, E. P., W. Zhang, D. Y. Lanclos, J. A. Masson, and S. N. Morris. 1999. Experimental herbicides for weed control in rice. Proc. South. Weed Sci. Soc. 52:16.
Zhang, W., E. P. Webster, J. L. Griffin, and D. Y. Lanclos. 1999. Effect of a glufosinate application on hybridization potential for glufosinate-resistant rice lines to red rice. Weed Sci. Soc. Am. Abstr. 39:10.
Zhang, W., E. P. Webster, J. L. Griffin, and D. Y. Lanclos. 1999. Hybridization potential from glufosinate-resistant rice lines to red rice (Oryza sativa) as affected by glufosinate treatment. Proc. Louis. Plant Protection Assn. 9:54.
Zhang, W., E. P. Webster, J. A. Masson, and J. L. Griffin. 1999. Hybridization potential of glufosinate resistant lines to red rice (Oryza sativa). Proc. South. Weed Sci. Soc. 52:232.