Evaluating the Potential Hormetic Effect of Herbicides on Sugar Beet

1. Evaluating the Potential Hormetic Effect of Herbicides on Sugar Beet Don W. Morishita, Joel Felix, Joey Ishida, Rabecka Hendricks, Kathrin LeQuia, Alexis Thompson

2. Introduction • Sugar beet yields continue to increase • Processing capacity becoming a limiting factor • Desire to increase sugar yield without increasing root yield • Growth regulators • Herbicides as hormetic agents • Hormesis- dose response phenomenon characterized by low dose stimulation and high dose inhibition (Calabrese and Baldwin) • Plants- positive response to low dose exposure to environmental agents; high dose is inhibitory or toxic

3. Introduction • Glyphosate on sugarcane • Registered for use to increase sucrose content as a pre-harvest application • Apply 0.14 to 0.42 lb ae/A (157 to 470 g ae ha-1) 3 to 7 weeks before harvest of ratoon cane only. • Sulfometuron on sugarcane • Increased sucrose content at 0.14 to 0.28 oz ai/A (10 to 20 g ai ha-1). • Simazine on corn and wheat • Increased protein content

4. Introduction • Glyphosate increased barley grain yield and fresh weight • Growth regulator herbicides- anecdotal evidence of hormetic effect from drift onto sensitive crops

5. Objective • Evaluate multiple herbicides applied at sub-lethal rates during the growing season to determine hormesis potential

6. Materials and Methods • Locations- • UI Kimberly Research & Extension Center • OSU Malheur Experiment Station • Varieties- • Idaho- SX1534RR • Oregon- BTS 27RR20 • Irrigation- • Idaho- sprinkler • Oregon- furrow

7. Materials and Methods • Herbicides evaluated- Group 2 ALS inhibitor • Florasulam (1X = 0.21 oz ai/A [15 g ha-1]) • Turf, wheat, barley • Triazolopyrimidine • Rimsulfuron (1X = 0.25 oz ai/A [18 g ha-1]) • Potato, stone and pome fruit trees • Sulfonylurea

8. Materials and Methods • Herbicides evaluated- Group 2 Synthetic auxin • Fluroxypyr (1X = 0.175 lb ae/A [196 g ha-1]) • Wheat, barley, oat • Carboxylic acid • MCPA (1X = 0.33 lb ae/A [370 g ha-1]) • Wheat, barley, oat, other crops • Phenoxy acetic acid • Proportional rates used- • 0, 0.01, 0.1, 1, and 10% of the 1X rates

9. Materials and Methods • Experimental design • 4 by 4 factorial randomized complete block • 4 herbicides • 4 herbicide rates • 6 replications • Data analysis • Crop injury • Sugar beet root and sucrose yield, % sugar, nitrates, conductivity • Dose-response regression analysis • Used Proc GLIMMIX in SAS 9.4 • Means separated at α = 0.05 using Least Square Means

10. Results

11. Results • Crop injury minimal in both years at Oregon • Mostly <10% 7 DAA. • 2017- 17% injury with fluroxypyr at 10% rate 7 DAA • 2018- none observed • Crop injury in Idaho • 2017- 32% injury with fluroxypyr at 10% rate 7 DAA 2018- all injury ranged from 1-9% 7 DAA

12. Results • Nitrates and Conductivity • Unaffected by all treatments • Yield and sugar content response • Unable to model dose-response with any of the herbicides used • Used analysis of variance

13. Analysis of Variance

14. Sucrose Yield a a b b

15. Sucrose Yield a a a ab b

16. Sugar Content a ab b b

17. Sugar Content a a a a b

18. Summary and Conclusions • Several herbicides have been documented to have hormetic effect on various crop species. • Injury was negligible on root or sucrose yield or sugar content. • No single herbicide or rate stood out alone to provide higher sucrose yield or higher sugar content. • Rimsulfuron offers the greatest promise. • Only one application timing considered. • May be worth looking at other application timing(s).

19. Questions?