Response of Timothy Seed Crops to Plant Growth Regulators
Trinexapac-ethyl (Moddus) and Chlormequat Chloride (Manipulator)
Peace River Region (2020-2023)
Study lead: Calvin Yoder, Forage Seed Specialist
Trials conducted by: SARDA Ag Research and Peace Region Forage Seed Association
Compiled by Calvin L Yoder 1,2, Surendra Bhattarai1 and Talon Gauthier2. March 2025
1SARDA Ag Research. 2Peace Region Forage Seed Association.
Funded by: All the forage seed levy paying growers in Alberta and British Columbia and matching funds from the AAFC AgriScience Program and Results Driven Agriculture Research (RDAR).
Introduction
Plant growth regulators (PGRs) are used regularly on grass seed crops in the main grass seed growing areas throughout the world. They shorten internodes, increase stem thickness, and reduce plant heights which help to reduce lodging. Reducing lodging helps to improve pollination, harvestability and can increase seed yields. Research from Oregon has also shown the growth regulator trinexapac-ethyl to increase the number of seeds/spikelet and seeds/m2 in perennial ryegrass. The use of PGRs on grass seed crops is relatively new in Canada.
The main PGR used on cool season grass seed crops is trinexapac-ethyl (TE). Chlormequat chloride (CCC) is also used to a lesser degree on some species in some countries. Research in New Zealand showed a tank mix of TE+CCC was very effective at increasing grass seed yields. The TE, trade name Moddus (11.3% EC), was registered in 2020 in Canada for use on wheat, barley and oats and is distributed by Syngenta. The CCC, trade name Manipulator (620 EC), was registered in 2018 in Canada for use on wheat, barley, and oats and is distributed by Belchim Crop Protection Canada (Figure 1).
The objective of the study was to determine the effect of TE, CCC and TE + CCC mixture applied at 2-3 node stage and early heading stage on plant height, lodging, seed yield and seed dockage of timothy.
Methods
Trials were conducted on grower fields from 2020 to 2023. Areas with uniform plant stands were selected within each field. Eight site years of data was collected. Age of stands ranged from two to five years old.
Individual plots were staked to an area of 3 m wide by 10 m long. Experiments were laid out in randomized complete block design with four replications. Growth regulator treatments as shown in Table 1 were applied with a 2m handheld boom (4 nozzle TeeJet 80001) pressurized by a propane sprayer. The sprayer and walking speed was calibrated to provide 100 l/ha of water at a pressure of 270 kPa.
Growth regulator treatments were applied at two different growth stages. Stage 1 ranged from 2-node to 3node stage of growth while Stage 2 was at early heading. The two stages of application differed by a minimum of 7 days between dates. Site, application and harvest information is shown in Table 2.
Visual lodging ratings were taken at flowering stage and prior to swathing. Lodging was rated in 1-9 scale (1=erect, 9=flat) (Barry et al. 2003). Harvesting was done by swathing down the middle of each plot with a Zurn 540 High Clearance Tool Carrier and then combining with a WinterSteiger plot combine with a pickup header generally a week after swathing. Harvested area of an individual plot was 15 m2. Samples were dried, cleaned, and weighed to determine seed yield and dockage.
Table 1. Growth regulator treatments applied to timothy seed stands.
*Costs based on 2023 SRP of $440 for a 10 liter jug for Moddus and $270 for a 10 liter jug of Manipulator
Table 2. Site and spray information for growth regulator trials on first year production stands of timothy.
Precipitation during the growing season varied from average to above average in 2020 and 2022 while it was well below average in 2021 and 2023. Lodging was an issue in 2020 and 2022. The effects of plant growth regulators on timothy seed crops averaged over eight sites is shown in Table 3. All PGR treatments reduced plant heights and lodging on timothy (Figures 4 and 5). Tables 3 and 4 and Figures 6 and 7 show the effects of PGRs on seed yields. All PGR treatments increased seed yields.
3. Response of
to plant growth regulators applied at 2-3 node (A) and heading (B) stage averaged over eight sites from 2020 to 2023.
*Lodging ratings are 1 = upright to 9 = flat.
CV - coefficient of variance
a,b,c - results followed by the same letter do not significantly differ (p = 0.001, Student-Newman-Keuls)
Figure 4. Response of plant height of timothy to growth regulators applied at 2-3 node (A) and heading (B) stage averaged over eight sites from 2020 to 2023.
Table 4. Response of seed yield of timothy to growth regulators applied at 2-3 node (A) and heading (B) stage averaged over eight sites from 2020 to 2023.
Lodging Score (1=upright, 9=flat)
a,b,c; A,B,C - results followed by the same letter do not significantly differ (p = 0.001)
Treatment
Figure 5. Response of lodging (1=upright and 9=flat) at flowering stage of timothy to growth regulators applied at 2-3 node (A) and heading (B) stage averaged over eight sites from 2020 to 2023.
Seed Yield (kg/ha)
a,b,c - results followed by the same letter do not significantly differ (p = 0.001)
Treatment
Figure 6. Response of seed yield of timothy to plant growth regulators applied at 2-3 node (A) and heading (B) stage averaged over eight sites from 2020 to 2023.
Average Check Yield = 654 kg/ha
Figure 7. Response of seed yield (percent of check) of timothy to plant growth regulators applied at 2-3 node (A) and heading (B) stage averaged over five stands under average to above average moisture conditions (2020 and 2022) Percent of Check
Summary and Recommendations
• The applications of PGRs to established timothy were generally effective at reducing plant heights and lodging, especially when applied at the 2-3 node stage. All PGRs significantly reduced the plant height as compared to the check but TE and TE+CCC at both stages of application were more effective at reducing plant heights than CCC.
• Seed yields were significantly increased by the application of PGRs, particularly when applied at the 23 node stage. Seed yields ranged from 86 to 138% of the check depending on the field, growth regulator type and stage of application. Although all PGRs applied at 2-3 node stage were effective in increasing seed yield, CCC at the 2-3 node stage application showed higher than the check yield at all of the sites ranging from 101% to 122% with an average increase of 10% seed yield over the check.
• Increases in seed yield over the check for PGRs applied at the 2-3 node stage averaged over five sites where moisture conditions were average to above average were 119% (TE1x), 114% (CCC1x) and 116% (TE+CCC). Average check seed yields of the five sites was 654 kg/ha.
• Further studies should be conducted to fine tune rates, timing, and stage of application with PGR mixtures on timothy plant heights, lodging and seed yields. Studies should also be conducted to evaluate the effects of tank mixing the growth regulators with herbicides as the stage of applications are quite similar.
References
Belchim Crop Protection Canada – Manipulator Product Label. https://manipulatorpgr.belchimcanada.com/wpcontent/uploads/2023/06/Label-English.pdf
Berry, P. M., Spink, J., Sterling, M.,&Pickett, A. A. (2003).Methods for rapidly measuring the lodging resistance of wheat cultivars. Journal of Agronomy and Crop Science, 189(6), 390–401. https://doi.org/10.1046/j.09312250.2003.00062.x
Syngenta – Moddus Product Label. https://assets.syngenta.ca/pdf/ca/labels/Moddus_33930_en_ pamphlet. pdf
Yoder, C., and SARDA. 2023. Effects of Growth Regulators and Herbicides on Timothy - Sunset House 2023. ARM DAT File.
Yoder, C., and SARDA. 2022. Effects of Growth Regulators on Timothy - Sunset House 2022. ARM DAT File
Yoder, C., and SARDA. 2022. Effects of Growth Regulators on Timothy - Guy 2022. ARM DAT File
Yoder, C., and SARDA. 2022. Effects of Growth Regulators on Timothy - Whitemud 2022. ARM DAT File
Yoder, C., and SARDA. 2021. Effects of Growth Regulators and Fungicides on Timothy - Whitemud 2021. ARM DAT File
Yoder, C., and SARDA. 2021. Effects of Growth Regulators and Fungicides on Timothy - Sunset House 2021. ARM DAT File
Yoder, C., and SARDA. 2020. Effects of Growth Regulators on Timothy – Sunset House 2020. ARM DAT File
Yoder, C., and SARDA. 2020. Effects of Growth Regulators on First Year Timothy Seed Crop - Whitemud 2020. ARM DAT File
Yoder, C., and SARDA. 2019. Effects of TE and CCC Growth Regulators on Established Timothy - Sunset House 2019. ARM DAT File
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