Pendimethalin as a Delayed Preemergence Herbicide in Rice

Bulletin 1064 -- November 1996

Joe E. Street
Plant Physiologist
Delta Research and Extension Center
Stoneville, Mississipppi

Dendra J. Lanham
Research Assistant I
Delta Research and Extension Center Stoneville, Mississippi

   

This research was supported in part by the Mississippi Rice Promotion Board and American Cyanamid Company.

Published by the Office of Agricultural Communications, Division of Agriculture, Forestry, and Veterinary Medicine, Mississippi State University. Edited by Keith H. Remy, Senior Publications Editor. Cover designed by Garland Carey, Student Artist.

Introduction
Materials and Methods
Results and Discussion
Literature Cited
Table 1.
Table 2.
Table 3.
Table 4.




Introduction

      Weeds that have traditionally caused few problems have become more important during the past decade because of continued use of propanil (Stam®) and the introduction of new short-statured, short-season rice cultivars.

      Annual grass species found in the southern states, such as barnyardgrass [Echinochloa crus-galli (L.) Beauv.] and bearded sprangletop [Leptochloa fascicularis (Lam.) Gray], cause serious problems in rice fields. In comparison to bearded sprangletop, barnyardgrass matures later and is more competitive in rice (3). It is taller than bearded sprangletop and has larger leaves and stems. Full-season competition from barnyardgrass can cause up to 70% yield reduction while sprangletop can cause up to 36% yield loss (12). Carey, et al. (2) noted that bearded sprangletop interference with Lemont for 63, 70, and 130 days after rice emergence resulted in 11, 21, and 50% yield reductions, respectively. Even though losses from sprangletop are not as high as from barnyardgrass, it is considered a hard-to-control weed because of inadequate control from propanil applications (5, 10, 12, 13).

      Thiobencarb (Bolero®) is the only residual herbicide currently being used for preemergence rice applications in fields with a sprangletop history (3). Most rice yield reductions are caused by interference of multiple species rather than a single species. Therefore, rice production is increased when all weeds are controlled (11).

      Quinclorac (Facet®) was registered for rice use in the United States in 1992, with applications ranging from preemergence to postemergence. It can be applied preemergence to dry soil (PRE-D), preemergence to moist soil (PRE-M), and early or late postemergence (EPOST/ LPOST) without causing rice injury (14, 15). Applications at 0.38 or 0.5 lb ai/A preemergence to dry or moist soil provided greater than 80% control of barnyardgrass without injuring rice (15).

      Dinitroanaline herbicides, such as trifluralin (Treflan®) and pendimethalin (Prowl®), are commonly used in several crops for residual control of annual grasses (4). As a group, they are selective preemergence herbicides that prevent weeds from emerging through the soil surface.

      Pendimethalin is a low-volatile and low-mobile dinitroanaline containing low water solubility properties (7, 9). Cultivation practices, moisture conditions, soil temperature, and soil type influence herbicide persistence (7). Pendimethalin is most persistent in silty clay soil and persists longer when it is soil incorporated rather than applied to the surface (7, 18). Surface applications have breakdowns ranging from 75 to 80% after 7 days (7).

      Disintegration of this herbicide occurs best in flooded, anaerobic conditions rather than in aerobic conditions, with degradation enhancement occurring when increased soil moisture is paired with high temperatures (8). One study reported a 35% reduction of pendimethalin without leaching when rain occurred the first day after application (7).

      Preemergence application of pendimethalin has been successful in both conventional and no-till corn (1). Application of 1.0 lb ai/A resulted in less than 15% injury to corn while providing 90% control of large crabgrass (6). On the other hand, severe sorghum injury occurred when treated soil remained wet at the time of emergence. However, crop injury was not noted when soil remained dry and sorghum emerged quickly (1).

      Pendimethalin has been effectively used in rice since 1981 as a residual herbicide when tank-mixed with propanil. Street (16) reported postemergence applications of propanil tank-mixed with pendimethalin resulted in control of barnyardgrass and bearded sprangletop, whereas propanil used alone did not provide adequate sprangletop control. Postemergence applications of pendimethalin plus propanil have been shown to attain 95% barnyardgrass control and 90% control of sprangletop without causing rice injury (14).

      Preemergence applications of pendimethalin have been known to injure emerging rice (3). Sensitivity to pendimethalin could be related to mesocotyl length, which varies among cultivars and could make some varieties more susceptible to injury. Sullivan reports some varieties are more tolerant to preemergence applications of pendimethalin because they have shorter mesocotyls (17). One suspected reason for this is subsequent development of the coleoptile node 0.5-inch or more below the treated soil surface. More susceptible varieties possess mesocotyls that are more elongate and allow the coleoptile node to develop at the soil surface and sustain more injury from the herbicide. Semidwarf rice cultivars often have a short mesocotyl, which may allow them to escape injury (17).

      The objective of this study was to evaluate pendimethalin as a preemergence or delayed preemergence herbicide, applied alone, or in tank mixtures with quinclorac (Facet) for use in rice.




Materials and Methods

      Experiments were conducted at the Delta Branch Experiment Station, Stoneville, Mississippi, in 1992 and 1993. Soil type was Sharkey clay (Vertic Haplaquept) with 1.2% organic matter content and pH of 7.4. Plots were 8 feet wide by 15 feet long. In 1992, plots were overseeded with barnyardgrass prior to final land preparation and immediately prior to seeding rice. Lemont rice was drill-seeded 0.75-inch deep in 8-inch rows at a seeding rate of 90 lb/A. Standard rice production practices were used to maximize yield. Test design was a randomized complete block replicated four times.

      Pendimethalin was applied as a preemergence herbicide at 1 and 2 lb ai/A one day before flushing. Delayed preemergence applications were made 1, 4, and 7 days after flushing at a rate of 1 and 2 lb ai/A. Tank mixtures of pendimethalin plus quinclorac (1 + 0.38 lb ai/A) were included along with thiobencarb (4 lb ai/A) as standards. Herbicides were applied with a CO2-pressurized backpack sprayer delivering 20 GPA (gallons per acre) carrier volume at a pressure of 26 psi. Stand counts were made 2 weeks after treatment each year.

      In 1992, rice injury and barnyardgrass control were rated 2 and 4 weeks after treatment. In 1993, only rice injury ratings were taken because of the removal of the barnyardgrass variable. Ratings were visually estimated on a scale of 0 to 100%, with 0 indicating no injury or weed control and 100 indicating dead rice or complete weed control. Data for each year were subjected to analysis of variance procedures and means were separated using the Waller-Duncan multiple range test (P= 0.05). There was a significant year by treatment interaction, thus data are presented by year.




Results and Discussion

      Overseeding with barnyardgrass allowed effective evaluation of control by pendimethalin applied preemergence and delayed preemergence. At 2 weeks after treatment, barnyardgrass control was > 96% with pendimethalin when applied alone or mixed with quinclorac (Table 1). Residual control of barnyardgrass was 86% at 4 weeks after treatment with preemergence applications of pendimethalin, while residual control from delayed preemergence applications ranged from 68% to 82% (Table 1). All delayed preemergence applications of pendimethalin + quinclorac consistently provided 94 to 96% residual barnyardgrass control at 4 weeks after treatment (Table 1). Thiobencarb controlled barnyardgrass up to 63% by 4 weeks after treatment for all timings (Table 1).

      Rice injury was primarily stunting and yellowing. In 1992, preemergence (1 day before flushing) application of pendimethalin caused significant injury and was greater than injury caused by delayed preemergence application in most cases. When rated 2 weeks after treatment, application of 1 lb ai/A pendimethalin at 1, 4, or 7 days after flushing caused < 15% rice injury; however, at 4 weeks after treatment, rice had recovered and little or no injury was observed (Table 2). Application of 2 lb ai/A, which would simulate overlap areas, caused 29% injury when applied 7 days after flushing and this injury persisted at the 4 weeks after treatment rating (Table 2). Application of 2 lb ai/A pendimethalin to moist soil (1 or 4 days after flushing) injured rice 15 and 20%, respectively (Table 2).

      In 1993, pendimethalin applied preemergence at 1 or 2 lb ai/A injured rice 45 and 63%, respectively, at 2 weeks after treatment (Table 2). Injury was still evident at 4 weeks after treatment. When applied 1, 4, or 7 days after flushing, pendimethalin at 1 lb ai/A did not significantly injure rice. However, 2 lb ai/A caused significant injury at 4 weeks after treatment when applied 1 day after flushing (31%) and 7 days after flushing ( 23%) (Table 2). No significant injury was observed with thiobencarb or the tank mixture of pendimethalin and quinclorac at any application timing.

      When applied preemergence in 1992, both rates of pendimethalin reduced rice stands (Table 3). Rice stand was also reduced when pendimethalin was applied at 1 lb ai/A 4 or 7 days after flushing (Table 3). However, when 1 lb ai/A pendimethalin was tank-mixed with quinclorac, rice stand was not reduced at any delayed preemergence application timing as compared to the untreated control. Thiobencarb applied at 1 and 7 days after flushing did not reduce rice stand at any application (Table 3). In 1993, rice stand was reduced by pendimethalin when applied 1 day before flushing at both rates and at 1 day after flushing when applied at 2 lb ai/A when compared to thiobencarb applied 1 or 7 days after flushing but not the untreated control (Table 3). No other treatment reduced rice stand in 1993 at any application timing.

      In 1992, rough rice yields generally reflect weed control and thus the effect of pendimethalin on yield was difficult to assess (Table 4). All treatments resulted in yields greater than the untreated control. Rice yields were higher with treatment of pendimethalin plus quinclorac than treatment with pendimethalin alone at 1 lb ai/A applied 4 or 7 days after flushing (Table 4). Reduced yields could have resulted from reduced stands with pendimethalin application at 1 or 7 days after flushing. Initial injury from pendimethalin did not translate to reduced yields in 1992.

      In 1993, barnyardgrass was not present; thus, the untreated control yield was 8,190 lb/A, which was higher than the yields from preemergence treatment with pendimethalin but not thiobencarb (Table 4). Rice yields were similar with all treatments applied at 1, 4, or 7 days after flushing.

      In summary, these data show that pendimethalin at 1 lb ai/A provides good barnyardgrass control when applied delayed preemergence without significant rice injury. Pendimethalin applied preemergence prior to flushing may cause significant rice injury and yield reduction.




Literature Cited

  1. Brown, S. M., J. M. Chandler, J. E. Morrison, Jr., and D. C.Bridges. 1987. Placement techniques for preemergence applicationsof pendimethalin in grain sorghum (Sorghum bicolor). Weed Sci. 35:678-681.
  2. Carey, F. V. III., R. J. Smith, Jr., and R. E. Talbert. 1994. Interference duration of bearded sprangletop (Leptochloa fascicularis) in rice (Oryza sativa). Weed Sci. 42:180-183.
  3. Guy, C. Jr., F. Baldwin, and R. Helms. 1994. Rice weed control. p. 28-29. in R. Helms, ed. Rice Production Handbook. Coop. Ext. Serv. Print Shop, Little Rock, AR.
  4. Jordan, D., A. Burns, and J. Barnes. 1994. Rice weed control research in northeast Louisiana. La. Agric. Exp. Stn., St. Joseph, LA.
  5. Khodayari, K., P. Natstasi, and R.J. Smith, Jr. 1989. Fenoxaprop for grass control in dry seeded rice (Oryza sativa). Weed Tech. 3:131-135.
  6. Rhodes, G.N., Jr., R.N. Hayes, W.A. Krueger, R.F. Montgomery, and T.C. Mueller. 1995. Preemergence corn herbicides are more similar than different. Proc. SWSS. 48:83.
  7. Savage, K.E., and T.E. Jordon. 1980. Persistence of three dinitroanaline herbicides on the soil surface. Weed Sci. 28:105-110.
  8. Savage, K.E. 1978. Persistence of several dinitroanaline herbicides as affected by soil moisture. Weed Sci. 26:465-471.
  9. Schleicher, L.C., P.J. Shea, R.N. Stouggaard, and D.R. Tupy. 1995. Efficacy and dissipation of dithiopyr and pendimethalin in perennial ryegrass (Lolium perenne) turf. Weed Sci. 43:140-148.
  10. Smith, R.J., Jr. 1988. Weed control in water- and dry-seeded rice, Oryza sativa. Weed Tech. 2:242-250.
  11. Smith, R.J., Jr. 1988. Weed thresholds in southern U.S. rice, Oryza sativa. Weed Tech. 2:232-241.
  12. Smith, R.J., Jr. 1983. Competition of bearded sprangletop (Leptochloa fascicularis) with rice (Oryza sativa). Weed Sci.31:120-123.
  13. Smith, R.J., Jr. 1975. Herbicides for control of Leptochloa panicoides in water-seeded rice. Weed Sci. 23:36-39.
  14. Stauber, L.G., P. Nastasi, R.J. Smith, Jr., A.M. Balatazar, and R.E. Talbert. 1991. Barnyardgrass (Echinochloa crus-galli) and bearded sprangletop (Leptochloa fascicularis) control in rice (Oryza sativa). Weed Tech. 5:337-344.
  15. Street, J.E. and T.C. Mueller. 1993. Rice (Oryza sativa) weed control with soil applications of Facet. Weed Tech. 7:600-604.
  16. Street, J.E., M.E. Kurtz, E.P. Richard, Jr., and T.C. Miller. 1983. Pendimethalin for grass control in rice. MAFES Res. Highlights 46:7-8, Feb. 1983.
  17. Sullivan, K.L., and M.G. Merkele. 1980. Differential response of various sorghum varieties to preemergence application of pendimethalin. Proc. SWSS 33:46.
  18. Zimdahl, R.L., P. Catizone, and A.C. Butcher. 1984. Degradation of pendimethalin in soil. Weed Sci. 32:408-412.

NOTE: Tolerance or exemption from tolerance has not been established for all uses of pesticides reported here. Pesticides were used in accordance with EPA Experimental Use Regulations. Information included is not to be construed either as a recommendation for use or as an endorsement of a specific product by Mississippi State University or the Mississippi Agricultural and Forestry Experiment Station.




Table 1. Barnyardgrass control in rice with pendimethalin in 1992.

Barnyardgrass

Control2
Timing1 Herbicide Rate 2 WAT 4 WAT

lb ai/a %

Untreated 0 0 e 0 j
1 DAY BEFORE FLUSH
PRE

Pendimethalin 1 99 a 86 abc

Pendimethalin 2 99 a 86 abc

Thiobencarb 4 91 d 56 ghi
1 DAY AFTER FLUSH
D-PRE

Pendimethalin 1 98 ab 73 def

Pendimethalin 2 99 a 79 cde

Pendimethalin + Quinclorac 1 + 0.38 99 a 94 ab

Thiobencarb 4 91 d 53 hi
4 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 96 bc 68 efg

Pendimethalin 2 99 a 81 bcd

Pendimethalin + Quinclorac 1 + 0.38 99 a 96 a

Thiobencarb 4 94 c 63 fgh
7 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 98 ab 71 def

Pendimethalin 2 98 ab 82 bcd

Pendimethalin + Quinclorac 1 + 0.38 99 a 94 ab

Thiobencarb 4 91 d 50 hi
1PRE=preemergence; D-PRE=delayed preemergence.
2Means followed by the same letter are not significantly different according to Waller-Duncan's Multiple Range test (P= 0.05)




Table 2. Effect of pendimethalin on rice injury in 1992 and 1993.

Rice Injury 2

1992 1993
Timing1 Herbicide Rate 2 WAT 4 WAT 2 WAT 4 WAT

lb ai/a %

Untreated 0 0 f 0 c 0 c 0 e
1 DAY BEFORE FLUSH
PRE

Pendimethalin 1 28 ab 11 b 45 b 43 ab

Pendimethalin 2 35 a 25 a 63 a 53 b

Thiobencarb 4 5 ef 0 c 0 c 0 e
1 DAY AFTER FLUSH
D-PRE

Pendimethalin 1 13 cde 0 c 6 c 8 de

Pendimethalin 2 15 cd 3 bc 38 b 31 bc

Pendimethalin + Quinclorac 1 + 0.38 8 def 0 c 1 c 0 e

Thiobencarb 4 3 f 0 c 0 c 3 e
4 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 13 cde 0 c 0 c 9 de

Pendimethalin 2 20 bc 10 b 0 c 6 e

Pendimethalin + Quinclorac 1 + 0.38 8 def 0 c 0 c 5 e

Thiobencarb 4 0 f 0 c 0 c 8 de
7 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 15 cd 6 bc 1 c 9 de

Pendimethalin 2 29 a 22 a 4 c 23 cd

Pendimethalin + Quinclorac 1 + 0.38 18 c 4 bc 0 c 4 e

Thiobencarb 4 3 f 0 c 0 c 1 e
1PRE=preemergence; D-PRE=delayed preemergence.
2Means followed by the same letter are not significantly different according to Waller-Duncan's Multiple Range test (P= 0.05).




Table 3. Effect of pendimethalin on stand of rice in 1992 and 1993.

Rice Stand2
Timing1 Herbicide Rate 1992 1993

lb ai/a plant/m row

Untreated 0 57 ab 25 ab
1 DAY BEFORE FLUSH
PRE

Pendimethalin 1 38 cde 14 b

Pendimethalin 2 28 e 14 b

Thiobencarb 4 61 a 23 ab
1 DAY AFTER FLUSH
D-PRE

Pendimethalin 1 42 b-e 21 ab

Pendimethalin 2 39 cde 14 b

Pendimethalin + Quinclorac 1 + 0.38 43 b-e 28 ab

Thiobencarb 4 53 abc 36 a
4 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 36 cde 26 ab

Pendimethalin 2 35 de 22 ab

Pendimethalin + Quinclorac 1 + 0.38 47 a-d 24 ab

Thiobencarb 4 63 a 22 ab
7 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 38 cde 28 ab

Pendimethalin 2 42 b-e 27 ab

Pendimethalin + Quinclorac 1 + 0.38 47 a-d 28 ab

Thiobencarb 4 51 a-d 29 a
1PRE=preemergence; D-PRE=delayed preemergence.
2Means followed by the same letter are not significantly different acording to Waller-Duncan's Multiple Range test (P= 0.05).




Table 4. Effect of pendimethalin on yield of rice in 1992 and 1993.

Rice Yield2
Timing1 Herbicide Rate 1992 1993

lb ai/a lb/a

Untreated 0 3,570 g 8,190 ab
1 DAY BEFORE FLUSH
PRE

Pendimethalin 1 7,070 de 6,945 d

Pendimethalin 2 7,340 bcd 7,057 cd

Thiobencarb 4 7,030 de 8,384 a
1 DAY AFTER FLUSH
D-PRE

Pendimethalin 1 7,355 bcd 8,070 ab

Pendimethalin 2 7,330 cd 7,780 abc

Pendimethalin + Quinclorac 1 + 0.38 7,975 abc 8,075 ab

Thiobencarb 4 6,462 e 8,035 ab
4 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 7,246 cd 8,495 a

Pendimethalin 2 7,160 de 7,730 a-d

Pendimethalin + Quinclorac 1 + 0.38 8,540 a 8,300 ab

Thiobencarb 4 6,985 de 8,100 ab
7 DAYS AFTER FLUSH
D-PRE

Pendimethalin 1 6,815 de 7,780 abc

Pendimethalin 2 7,355 bcd 7,595 bcd

Pendimethalin + Quinclorac 1 + 0.38 8,095 ab 7,855 ab

Thiobencarb 4 5,575 f 8,165 ab
1 PRE=preemergence; D-PRE=delayed preemergence.
2 Means followed by the same letter are not significantly different according to Waller-Duncan's Multiple Range test (P= 0.05).   

A black line that separates the body text from footer information
Return to MSUcares Home