Weed Control in Sweet Bell Pepper Using Sequential Postdirected Applications of Pelargonic Acid

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  • 1 1Sugarcane Research Unit, Agricultural Research Service, U.S. Department of Agriculture, 5883 USDA Road, Houma, LA 70360
  • 2 2Division of Agriculture Sciences and Natural Resources, Oklahoma State University, Cooperative Extension Service, 1901 S. 9th Street, Durant, OK 74702

Pepper (Capsicum annuum) producers would benefit from additional herbicide options that are safe to the crop and provide effective weed control. Research was conducted in southeastern Oklahoma (Atoka County, Lane, OK) during 2010 and 2011 to determine the impact of pelargonic acid on weed control efficacy, crop injury, and pepper yields. The experiment included pelargonic acid applied unshielded postdirected at 5, 10, and 15 lb/acre, plus an untreated weedy control and an untreated weed-free control. ‘Jupiter’ sweet bell pepper, a tobacco mosaic virus-resistant sweet pepper with a 70-day maturity, was transplanted into single rows on 3-ft centered raised beds with 18 inches between plants (9680 plants/acre) on 28 May 2010 and 27 May 2011, respectively. Weeds included smooth crabgrass (Digitaria ischaemum), cutleaf groundcherry (Physalis angulata), spiny amaranth (Amaranthus spinosus), and yellow nutsedge (Cyperus esculentus). Pelargonic acid was applied postdirected each year in mid-June and then reapplied 8 days later. The 15-lb/acre pelargonic acid treatment resulted in the maximum smooth crabgrass control (56%) and broadleaf weed control (66%) at 1 day after the initial spray treatment (DAIT), and 33% yellow nutsedge control at 3 DAIT. Pelargonic acid at 15 lb/acre provided equal or slightly greater smooth crabgrass and broadleaf (cutleaf groundcherry and spiny amaranth) control compared with the 10-lb/acre application, and consistently greater control than the 5-lb/acre rate and the weedy control. Pelargonic acid was less effective at controlling yellow nutsedge than smooth crabgrass and broadleaf weeds. As the rate of pelargonic acid increased from 5 to 15 lb/acre, yellow nutsedge control also increased significantly for all observation dates. Increasing the pelargonic acid application rate increased the crop injury rating. The maximum crop injury occurred for each application rate at 1 DAIT with 7%, 8.0%, and 13.8% injury for pelargonic acid rates 5, 10, and 15 lb/acre, respectively. There was little or no new crop injury after the second postdirected application of pelargonic acid and crop injury following 3 DAIT for application rates was 2% or less. Only the 15-lb/acre pelargonic acid application produced greater fruit per hectare (4784 fruit/ha) and yields (58.65 kg·ha−1) than the weedy control (1196 fruit/ha and 19.59 kg·ha−1). The weed-free yields (7176 fruit/ha, 178.11 kg·ha−1, and 24.82 g/fruit) were significantly greater than all pelargonic acid treatments and the weedy control. Pelargonic acid provided unsatisfactory weed control for all rates and did not significantly benefit from the sequential applications. The authors suggest the pelargonic acid be applied to smaller weeds to increase the weed control to acceptable levels (>80%).

Abstract

Pepper (Capsicum annuum) producers would benefit from additional herbicide options that are safe to the crop and provide effective weed control. Research was conducted in southeastern Oklahoma (Atoka County, Lane, OK) during 2010 and 2011 to determine the impact of pelargonic acid on weed control efficacy, crop injury, and pepper yields. The experiment included pelargonic acid applied unshielded postdirected at 5, 10, and 15 lb/acre, plus an untreated weedy control and an untreated weed-free control. ‘Jupiter’ sweet bell pepper, a tobacco mosaic virus-resistant sweet pepper with a 70-day maturity, was transplanted into single rows on 3-ft centered raised beds with 18 inches between plants (9680 plants/acre) on 28 May 2010 and 27 May 2011, respectively. Weeds included smooth crabgrass (Digitaria ischaemum), cutleaf groundcherry (Physalis angulata), spiny amaranth (Amaranthus spinosus), and yellow nutsedge (Cyperus esculentus). Pelargonic acid was applied postdirected each year in mid-June and then reapplied 8 days later. The 15-lb/acre pelargonic acid treatment resulted in the maximum smooth crabgrass control (56%) and broadleaf weed control (66%) at 1 day after the initial spray treatment (DAIT), and 33% yellow nutsedge control at 3 DAIT. Pelargonic acid at 15 lb/acre provided equal or slightly greater smooth crabgrass and broadleaf (cutleaf groundcherry and spiny amaranth) control compared with the 10-lb/acre application, and consistently greater control than the 5-lb/acre rate and the weedy control. Pelargonic acid was less effective at controlling yellow nutsedge than smooth crabgrass and broadleaf weeds. As the rate of pelargonic acid increased from 5 to 15 lb/acre, yellow nutsedge control also increased significantly for all observation dates. Increasing the pelargonic acid application rate increased the crop injury rating. The maximum crop injury occurred for each application rate at 1 DAIT with 7%, 8.0%, and 13.8% injury for pelargonic acid rates 5, 10, and 15 lb/acre, respectively. There was little or no new crop injury after the second postdirected application of pelargonic acid and crop injury following 3 DAIT for application rates was 2% or less. Only the 15-lb/acre pelargonic acid application produced greater fruit per hectare (4784 fruit/ha) and yields (58.65 kg·ha−1) than the weedy control (1196 fruit/ha and 19.59 kg·ha−1). The weed-free yields (7176 fruit/ha, 178.11 kg·ha−1, and 24.82 g/fruit) were significantly greater than all pelargonic acid treatments and the weedy control. Pelargonic acid provided unsatisfactory weed control for all rates and did not significantly benefit from the sequential applications. The authors suggest the pelargonic acid be applied to smaller weeds to increase the weed control to acceptable levels (>80%).

As an important fresh-market vegetable crop in the United States, bell pepper domestic consumption (11 lb/person) continues to increase (Wells et al., 2013). The increasing gap between domestic production and U.S. demand provides an opportunity for increased domestic bell pepper production (Wells et al., 2013). There is also an increasing demand by consumers for more naturally produced vegetable crops (Webber et al., 2014). Therefore, producers growing bell peppers for markets that desire the use of more naturally occurring herbicides need alternatives that effectively provide season-long weed control. Although corn gluten meal has shown promise as an early season preemergent herbicide in vegetable production, any uncontrolled weeds can cause serious yield reductions (Webber et al., 2010). In general, there are limited options for control of annual broadleaf weeds in summer vegetables, and both organic and conventional producers would benefit from appropriate herbicides that effectively provide postemergent weed control (Kemble et al., 2013). Previous research with postemergence nonsynthetic contact herbicides in noncrop situations determined that these herbicides must be applied to very young or small weeds if acceptable weed control is expected (Webber et al., 2012a). A potential solution to this would be to increase weed control efficacy on larger weeds and decrease crop injury by using multiple or sequential postdirected herbicide applications (herbicides postdirected sprayed at the base of the crop rather than over-the-top).

Scythe® (Dow AgroSciences, Indianapolis, IN) is a fatty acid based, nonselective, synthetic contact herbicide consisting of 57% pelargonic acid and other related fatty acids. Pelargonic acid is naturally occurring in many plants and animals and present in many foods (U.S. Environmental Protection Agency, 2004). Pelargonic acid injures and kills plants by destroying the cell membranes, causing rapid desiccation of plant tissues (Webber et al., 2014). Chloroplast bleaching is seen within a short time after application (Senseman, 2007). The primary impact is the immediate decrease in intercellular pH with a resulting loss of cell membrane integrity (Senseman, 2007). Although pelargonic acid is not listed as a “certified organic” herbicide, it is seen as a more natural type herbicide for use in sustainable crop production (Webber and Shrefler, 2007).

Previous field studies determined that pelargonic acid applied at 5, 10.8, and 16.7 lb/acre as Scythe® at 3%, 6.5%, and 10% (v/v) at 100 gal/acre was effective as a broadcast postemergence contact herbicide when applied to small annual weeds (Webber and Shrefler, 2007). Webber et al. (2012b) determined that the application volume could be reduced from 100 to 40 gal/acre in postdirected applications in spring transplanted onion (Allium cepa) and still maintain good weed control with pelargonic acid applied at 5, 10, and 15 lb/acre. Unfortunately, crop injury and significant reduction in onion yields were observed with pelargonic acid application rates compared with the weed-free control.

Pelargonic acid in commercial formulations has potential as a nonselective postemergent contact herbicide for weeds in vegetable crops if application method and rate can be customized to individual crops to maintain weed control efficacy without reducing yields due to crop injury (Webber and Shrefler, 2007; Webber et al., 2005, 2012a, 2014). Research was conducted to determine the impact of sequential postdirected applications of pelargonic acid on weed control efficacy, crop injury, and yields in bell pepper.

Materials and methods

The experiments were conducted in 2010 and 2011 at the Oklahoma State University, Lane Agricultural Center, Lane, OK (lat. 34°17′N, long. 95°57′W) on a Bernow fine-loamy, siliceous, thermic Glossic Paleudalf soil. Before planting, the soil was fertilizedand prepared following Oklahoma Cooperative Extension Service recommendations (Motes et al., 1994). The experiment was a randomized complete block design with five treatments and four replications repeated across 2010 and 2011. ‘Jupiter’ sweet bell pepper, a tobacco mosaic virus-resistant sweet pepper with a 70-d maturity, were transplanted into single rows on 3-ft centered raised beds with 18 inches between plants (9680 plants/acre) on 28 May 2010 and 27 May 2011, respectively. Plots consisted of four 36-inch rows in plots 12 ft wide by 30 ft long. Soil moisture was maintained during the experiment by rainfall supplemented with overhead irrigation for a combined total of 55 cm of water from planting to harvest each year. All other required cultural practices, including insect and disease control, were completed according to Oklahoma State University recommendations (Motes et al., 1994).

Weed control treatments consisted of sequential applications of pelargonic acid applied at 5, 10, and 15 lb/acre, an untreated weedy control, and an untreated weed-free control. Weed-free plots were maintained by hand hoeing. Pelargonic acid was postdirected applied without shields [40 gal/acre, 0.4 gal/min (XR8004VS nozzle; Spraying Systems, Wheaton, IL)] to the base of the pepper plants on 16 June 2010 and 2011, 19 and 20 d after transplanting (DAT), respectively, and then reapplied 8 d later (24 June 2010 and 2011). No pepper flowers were present during either application. Although ‘Jupiter’ sweet bell pepper typically grows 60 to 90 cm tall, the lower leaves were inadvertently sprayed during both applications. At the time of initial applications, smooth crabgrass was 8 to 10 cm tall, cutleaf groundcherry was 5 cm tall, spiny amaranth was 8 to 10 cm tall, and yellow nutsedge was 10 to 15 cm tall. Smooth crabgrass represented 60% of the weed cover, while cutleaf groundcherry and spiny amaranth represented 35% and 3% of weed cover, respectively. Yellow nutsedge represented less than 2% of the weed cover.

Weed control and crop phytotoxicity ratings were collected at 1, 3, 7, 9, 11, 16, 21, and 28 DAIT (17 June to 13 July 2010 and 2011). Weed control ratings represent the percent weed control for a treatment compared with the weedy control. A visual rating system of 0% to 100% was used, 0% representing no weed control and 100% representing complete weed control. The visual ratings were focused on the percentage groundcover that the weed control produced. For crop response to the treatments, a 0% to 100% visual rating system was used in which 0% represented no crop injury (necrosis) and 100% represented crop death. The visual ratings were based on visual damage to the crop leaves. Weed control and crop injury data were converted using an arcsine transformation to facilitate statistical analysis and mean separation to normalize data within the parameters suggested by Ahrens et al. (1990). Marketable pepper fruit were harvested on 12 Aug. 2010 (76 DAP) and 11 Aug. 2011 (76 DAP). Marketable fruit was determined by using U.S. Department of Agriculture standards (USDA, 2005). Only mature, green, unblemished fruit that were at least 2.5 inches long and 2.5 inches in diameter were determined to be marketable, which could include U.S. Fancy, U.S. No. 1, and U.S. No. 2 (USDA, 2005). All fruit in these three grades were combined to provide a total marketable yield in pounds per plot and total marketable yield (kilograms per hectare). All data (weed control ratings, crop injury and fruit yields) were subjected to analysis of variance (SAS version 9.2; SAS Institute, Cary, NC) and mean separation using least significant difference with P = 0.05.

Results and discussion

There were no significant year-by-treatment interactions for weed ratings (Tables 13), crop injury ratings (Table 4), or yield data (Table 5); therefore, the data presented are averaged across 2010 and 2011.

Table 1.

Smooth crabgrass control as a result of sequential postdirected applications of pelargonic acid (PA) applied at 5, 10, and 15 lb/acre in bell pepper averaged across years in 2010 and 2011, at Lane, OK.

Table 1.
Table 2.

Broadleaf (cutleaf groundcherry and spiny amaranth) weed control as a result of sequential postdirected applications of pelargonic acid (PA) applied at 5, 10, and 15 lb/acre in bell pepper averaged across years in 2010 and 2011 at Lane, OK.

Table 2.
Table 3.

Yellow nutsedge control as a result of sequential postdirected applications of pelargonic acid (PA) applied at 5, 10, and 15 lb/acre in bell pepper averaged across years in 2010 and 2011 at Lane, OK.

Table 3.
Table 4.

Bell pepper injury as a result of sequential postdirected applications of pelargonic acid (PA) applied at 5, 10, and 15 lb/acre averaged across years in 2010 and 2011 at Lane, OK.

Table 4.
Table 5.

Impact of sequential postdirected applications of pelargonic acid (PA) applied at 5, 10, and 15 lb/acre on marketable bell pepper fruit number and yield averaged across years in 2010 and 2011 at Lane, OK.

Table 5.

Weed control.

Control of smooth crabgrass, 56% (Table 1), and broadleaf weeds (cutleaf groundcherry and spiny amaranth), 66% (Table 2), peaked with the 15-lb/acre application rate at 1 DAIT, while yellow nutsedge peaked at 3 DAIT with 33% control (Table 3). Smooth crabgrass control decreased for all application rates from initial weed control ratings at 1 DAIT until 9 DAIT (Table 1), 1 d after the sequential application, where smooth crabgrass control peaked a second time and then tended to decrease through the remainder of the weed control ratings. In general, the broadleaf weed control ratings follow the same trend as the smooth crabgrass weed control ratings, with the exception that the 5- and 10-lb/acre applications reached their greatest control at 9 DAIT, 1 d after the sequential treatment (Table 2). Yellow nutsedge had the greatest inconsistencies among the different application rates and rating times (Table 3). The 5-lb/acre rate peaked at 3 DAIT (10%) and decreased from that point until the end of the ratings. The 10-lb/acre rate followed the typical trend of peaking at 1 DAIT (15%), decreasing at the 3 (9%) and 7 (8%) DIAT ratings, and producing a second peak at 9 DAIT (10%). The 15-lb/acre rate tended to follow the 10-lb/acre trend but with a slight delay, first peaking at 3 DAIT (33%), decreasing though the 9 DAIT rating (22%), and producing a second peak at 11 DAIT (28%). Pelargonic acid provided unsatisfactory weed control for all pelargonic acid rates and did not significantly benefit from the sequential applications (Tables 1, 2, and 3). Although Webber et al. (2014) showed good (>80%) control of the same grass (smooth crabgrass, 8 to 15 cm tall) and broadleaf (cutleaf groundcherry at 5 to 8 cm tall and spiny amaranth at 5 to 8 cm tall) weed species in yellow squash (Cucurbita pepo), we suggest the pelargonic acid be applied to smaller weeds to increase the weed control to acceptable levels (80% to 90%).

Pepper foliar injury.

Although the sequential postdirected application of pelargonic acid at 15-lb/acre rate resulted in the greatest weed control, it also produced the greatest crop injury (13.8%) at 1 DAIT (Table 4). Crop injury for all application rates decreased from their peaks at 1 DAIT to their lowest values at 28 DAIT, with only slight numerical increases following the sequential treatments at 9 DAIT (Table 4). In contrast, Webber et al. (2014) reported the greatest injury to yellow squash accrued at 9 DAIT with injury peaks at 1 and 9 DAIT for all applications rates (5, 10, and 15 lb/acre). It appears the differences in crop architecture between bell pepper’s initial more erect stance compared with yellow squash’s more bushy horizontally spreading canopy may account for less pepper injury from the pelargonic acid applications. There also may be a greater sensitivity to pelargonic acid for yellow squash compared with bell pepper, or at least, the varieties tested. Further research could determine if there is a crop or variety difference for pelargonic acid sensitivity and the factors effecting crop injury.

Pepper yields.

Pepper plants treated with pelargonic acid at 15 lb/acre yielded greater (4784 fruit/ha and 59 kg·ha−1) than pepper plants treated with pelargonic acid at 5 lb/acre (598 fruit/ha and 12.5 kg·ha−1) and 10 lb/acre (1196 fruit/ha and 13.8 kg·ha−1) (Table 5). The 15-lb/acre rate of pelargonic acid had significantly greater fruit/ha and kg·ha−1 than the weedy control (1196 fruit/ha and 19.6 kg·ha−1), while the 5- and 10-lb/acre rate produced equal or less than the weedy control. The weed-free treatment produced greater yields (7176 fruit/ha and 178.1 kg·ha−1) than any of the pelargonic acid treatments. The weed-free treatment also produced the heaviest average fruit weight (24.8 g/fruit) compared with the 5-, 10-, and 15-lb/acre treatments (21.0, 11.5, and 12.6 g/fruit, respectively) and the weedy control (16.4 g/fruit) (Table 5). The 5-lb/acre pelargonic acid rate produced 50% less fruit (598 fruit/ha) than the weedy control (1196 fruit/ha) in spite of producing 26%, 23%, and 10% maximum greater grass (1 DAIT), broadleaf (1 DAIT), and nutsedge (3 DAIT) control, respectively (Tables 13). This decrease in fruit per hectare with increased weed control with the 5-lb/acre application rate is a clear indication of the detrimental impact of the early herbicide injury (7%) with the postdirected application of pelargonic acid at 5 lb/acre (Table 4). The 10-lb/acre pelargonic acid rate produced the same number of fruit (1196 fruit/ha) than the weedy control (1196 fruit/ha), while providing initial weed control ratings of 38% grass (Table 1), 44% broadleaf (Table 2), and 15% nutsedge (Table 3) control with 8% crop injury (Table 4) at 1 DAIT. It was only when the 15-lb/acre rate provided 56% grass (Table 1), 66% broadleaf (Table 2), and 31% nutsedge (Table 3) control with 13.8% crop injury (Table 4) did a pelargonic acid application produced greater fruit per hectare (4784 fruit/ha) and yields (58.65 kg·ha−1) than the weedy control (1196 fruit/ha and 19.59 kg·ha−1) (Table 5).

Conclusions

The sequential application of pelargonic acid at 5, 10, and 15 lb/acre produced poor grass (≤56%), broadleaf (≤66%), nutsedge (≤33%) control, and significant crop injury, which resulted in reduced fruit production (fruit per hectare), yields (kilogram per hectare), and fruit weights (grams per fruit). The 15-lb/acre pelargonic acid rate should benefit sustainable crop producers by producing four times the fruit production (fruit per hectare) and 3 times the yield (kilogram per hectare) than the weedy control. The authors suggest that pelargonic acid be applied to smaller weeds to increase the weed control to acceptable levels (80% to 90%). The use of a hooded sprayer may also reduce crop injury without a significantly decrease in weed control. Another option would be the use of a suitable preemergence herbicide to reduce the weed population and height before the postemergence application of pelargonic acid.

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Literature cited

  • Ahrens, W.H., Cox, D.J. & Budhwar, G. 1990 Use of the arcsine and square root transformation for subjectively determined percentage data Weed Sci. 38 452 458

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  • Kemble, J.M., Ivors, K., Louws, E.J., Jennings, K.M. & Walgenbach, J.F. 2013 Southeastern U.S. 2013 vegetable crop handbook. Vance Publ., Lincolnshire, IL

  • Motes, J.E., Criswell, J.T. & Damicone, J.P. 1994 Pepper production. Oklahoma Coop. Ext. Serv., Fact Sheet HLA-6030

  • Senseman, S.A. (ed.). 2007. Herbicide handbook. 9th ed. Weed Sci. Soc. Amer., Lawrence, KS

  • U.S. Department of Agriculture 2005 United States standards for grades of sweet peppers. 27 June 2014. <http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5050318>

  • U.S. Environmental Protection Agency 2004 Pesticides: Regulating pesticides. Pelargonic acid (217500). 30 Sept. 2009. <http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_217500.htm>

  • Webber, C.L. III & Shrefler, J.W. 2007 Pelargonic acid weed control: Concentrations, adjuvants, and application timing. Proc. 26th Hort. Ind. Show. Ft. Smith, AR. p. 145–148

  • Webber, C.L. III, Shrefler, J.W., Brandenberger, L.P. & Davis, A.R. 2012a AXXE® (pelargonic acid) and Racer® (ammonium nonanoate): Weed control comparisons, p. 158–161. In: L. Brandenberger and L. Wells (eds.). 2011 Vegetable weed control studies. Oklahoma State Univ., Div. Agr. Sci. Natural Resources, Dept. Hort. Landscape Architecture MP-162

  • Webber, C.L. III, Shrefler, J.W., Brandenberger, L.P. & Davis, A.R. 2012b Pelargonic acid as a post-directed herbicide for onions. Proc. 2012 Hort. Ind. Show. Tulsa, OK. p. 148–151

  • Webber, C.L. III, Shrefler, J.W. & Langston, V.B. 2005 Weed control with pelargonic acid (2004) Lane, Oklahoma, p. 32–33. In: L. Brandenberger and L. Wells (eds.). 2004 Vegetable weed control studies. Oklahoma State Univ., Div. Agr. Sci. Natural Resources, Dept. Hort. Landscape Architecture MP-162

  • Webber, C.L. III, Shrefler, J.W. & Taylor, M.J. 2010 Influence of corn gluten meal on squash plant survival and yields HortTechnology 20 696 699

  • Webber, C.L. III, Taylor, M.J. & Shrefler, J.W. 2014 Weed control in squash (Cucurbita pepo L.) using sequential postdirected applications of pelargonic acid HortTechnology 24 25 29

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  • Wells, H.F., Thornsbury, S. & Bond, J. 2013 U.S. Department of Agriculture: Vegetable and pulses outlook. 27 June 2014. <http://usda.mannlib.cornell.edu/usda/ers/VGS//2010s/2013/VGS-03-29-2013.pdf>

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Contributor Notes

We thank Buddy Faulkenberry, Research Technician (USDA, ARS), for his leadership, field work, and data processing; Michael Mobbs and Conner Garison, student workers (USDA, ARS), for their field work and data entry; and Tony Goodson (OSU), Jaquie Pruit (OSU), and Lacey Howery (OSU) for assistance with field work.

Mention of trade names or commercial products in this article is solely for the purpose of providing scientific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap. The article cited was prepared by a USDA employee as part of his/her official duties. Copyright protection under U.S. copyright law is not available for such works. Accordingly, there is no copyright to transfer. The fact that the private publication in which the article appears is itself copyrighted does not affect the material of the U.S. Government, which can be freely reproduced by the public.

Corresponding author. E-mail: Webber@ars.usda.gov.

  • Ahrens, W.H., Cox, D.J. & Budhwar, G. 1990 Use of the arcsine and square root transformation for subjectively determined percentage data Weed Sci. 38 452 458

    • Search Google Scholar
    • Export Citation
  • Kemble, J.M., Ivors, K., Louws, E.J., Jennings, K.M. & Walgenbach, J.F. 2013 Southeastern U.S. 2013 vegetable crop handbook. Vance Publ., Lincolnshire, IL

  • Motes, J.E., Criswell, J.T. & Damicone, J.P. 1994 Pepper production. Oklahoma Coop. Ext. Serv., Fact Sheet HLA-6030

  • Senseman, S.A. (ed.). 2007. Herbicide handbook. 9th ed. Weed Sci. Soc. Amer., Lawrence, KS

  • U.S. Department of Agriculture 2005 United States standards for grades of sweet peppers. 27 June 2014. <http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5050318>

  • U.S. Environmental Protection Agency 2004 Pesticides: Regulating pesticides. Pelargonic acid (217500). 30 Sept. 2009. <http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_217500.htm>

  • Webber, C.L. III & Shrefler, J.W. 2007 Pelargonic acid weed control: Concentrations, adjuvants, and application timing. Proc. 26th Hort. Ind. Show. Ft. Smith, AR. p. 145–148

  • Webber, C.L. III, Shrefler, J.W., Brandenberger, L.P. & Davis, A.R. 2012a AXXE® (pelargonic acid) and Racer® (ammonium nonanoate): Weed control comparisons, p. 158–161. In: L. Brandenberger and L. Wells (eds.). 2011 Vegetable weed control studies. Oklahoma State Univ., Div. Agr. Sci. Natural Resources, Dept. Hort. Landscape Architecture MP-162

  • Webber, C.L. III, Shrefler, J.W., Brandenberger, L.P. & Davis, A.R. 2012b Pelargonic acid as a post-directed herbicide for onions. Proc. 2012 Hort. Ind. Show. Tulsa, OK. p. 148–151

  • Webber, C.L. III, Shrefler, J.W. & Langston, V.B. 2005 Weed control with pelargonic acid (2004) Lane, Oklahoma, p. 32–33. In: L. Brandenberger and L. Wells (eds.). 2004 Vegetable weed control studies. Oklahoma State Univ., Div. Agr. Sci. Natural Resources, Dept. Hort. Landscape Architecture MP-162

  • Webber, C.L. III, Shrefler, J.W. & Taylor, M.J. 2010 Influence of corn gluten meal on squash plant survival and yields HortTechnology 20 696 699

  • Webber, C.L. III, Taylor, M.J. & Shrefler, J.W. 2014 Weed control in squash (Cucurbita pepo L.) using sequential postdirected applications of pelargonic acid HortTechnology 24 25 29

    • Search Google Scholar
    • Export Citation
  • Wells, H.F., Thornsbury, S. & Bond, J. 2013 U.S. Department of Agriculture: Vegetable and pulses outlook. 27 June 2014. <http://usda.mannlib.cornell.edu/usda/ers/VGS//2010s/2013/VGS-03-29-2013.pdf>

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