Fungicide resistance in populations of the pink rot pathogen in Canada

Transcription

1 Fungicide resistance in populations of the pink rot pathogen in Canada Rick Peters Agriculture and Agri-Food Canada Charlottetown Research and Development Centre 2016 Manitoba Potato Production Days Canad Inns, Brandon, MB

2 Potato Pink Rot Causal Agent: Phytophthora erythroseptica

3 Symptoms - Tuber all underground tissues may be affected (roots, basal stems, stolons, tubers) tubers most commonly infected via stolons (tuber infection via eyes or lenticels in very wet autumns)

4 Management of Pink Rot with Ridomil Gold Mean % Necrosis Trt NB PE NB PE NB PE ON PE ON PE ON BR CK RD F RD IN

5 EC 50 (ppm) Sensitivity of P. erythroseptica to metalaxyl-m 2005 Canadian Survey Field 1 2 Alberta 5 6 Manitoba New Brunswick PEI 7 resistant isolates (14%) out of 49 isolates collected in total 2007: 2 isolates from Quebec = sensitive 1 isolate from NB = resistant

6 Prince Edward Island

7 2012 Pink Rot Survey Resistance of Phytophthora erythroseptica to Ridomil (metalaxyl-m) Prince Edward Island, Canada Total samples = 12 Total isolates = = Ridomil Sensitive = Ridomil Resistant

8 Sensitivity of P. erythroseptica to Ridomil Gold (metalaxyl-m) MHR MMR MS

9 2013 Pink Rot Survey Resistance of Phytophthora erythroseptica to Ridomil (metalaxyl-m) Prov. # samples # isolates % samples MS % samples MR % isolates MS % isolates MR NS PE NB QC ON MB AB BC Total

10 2014 Pink Rot Survey Resistance of Phytophthora erythroseptica to Ridomil (metalaxyl-m) Prov. # samples # isolates % samples MS % samples MR % isolates MS % isolates MR PE NB MB AB Total

11 2014 Alternative Management of Pink Rot Field Trial Cultivar = Shepody Reps = 4 (RCBD) Pathogen Inoculum 9913 (Strain sensitive to metalaxyl-m; Ridomil) 1204 (Strain resistant to metalaxyl-m; Ridomil) Treatments Control Inoculated Control Not Inoculated In-furrow: Orondis (oxathiapiprolin) In-furrow: Phostrol (phosphite) Foliar: Phostrol (phosphite) In-furrow: Serenade (Bacillus subtilis) In-furrow: Ridomil Gold (metalaxyl-m) In-furrow: Presidio (fluopicolide)

12 2014 Alternative Management of Pink Rot Field Trial

13 2014 Alternative Management of Pink Rot Field Trial

14 2014 Alternative Management of Pink Rot Field Trial

15 Tubers from plots inoculated with the pink rot pathogen

16 2014 Alternative Management of Pink Rot Field Trial Results

17 Implications and Next Steps Continue national survey on the incidence of Ridomil resistance in pathogen populations in Canada Data for individual farms can provide the basis for pink rot management decisions More research into alternative disease control strategies is needed Phosphites may play a more important role in the management of pink rot if Ridomil resistance becomes more widespread Other in-furrow treatments to manage pink rot in daughter tubers appear promising

18 Thoughts on Phosphites Foliar programs work very well for pink rot control when applied at the right rates % diseased tubers % disease 0 C PA PA PA PA PA PA X 5X 5X 3X 3X 3X

19 Thoughts on Phosphites Post-harvest programs are excellent at killing pathogen spores when applied soon after harvest % diseased tubers CON P CX C.5X C2X LB PR-RES PR-SEN

20 Significant control of silver scurf with post-harvest phosphite application Tracy Shinners-Carnelley, Peak of the Market, MB

21 Phosphorous acid Year Incidence (%) of silver scurf ~3 months in storage ~6 months in storage Water-treated control Phosphorous Acid Water-treated control Phosphorous Acid average Nora Olsen and team, Idaho

22 Adverse Physiological Effects of Phosphite noted in foliage and with seed used from plants receiving high field rates or in seed treated post-harvest therefore caution: safe rate for seed not yet determined - Plants usually catch up 1-2 weeks after emergence - Significant reduction in marketable yield has been recorded for some varieties in some years

23 Adverse Physiological Effects of Phosphite Khalil Al-Mughrabi, NB - Plants usually catch up 1-2 weeks after emergence - Significant reduction in marketable yield has been recorded for some varieties in some years

24 2013 Trial in Manitoba - Effect of phosphorus acid application on emergence and number of stems Darin Gibson and Donovan Fehr, Gaia Consulting Ltd

25 2013 Trial in Manitoba - Effect of phosphorus acid on potato yield. Yield (cwt/ac) Treatment > 3 oz > 6 oz Total 1 4 app Foliar Confine c c c 2 3 app Foliar Confine ab ab abc 3 2 app Foliar Confine abc ab abc 4 3 app Foliar Phos. 5.8 L/Ha bc bc bc 5 4 app Foliar Phos. 2.9 L/Ha a abc ab 6 Post Harvest Confine a a a 7 Post Harvest Phostrol abc abc abc 8 Untreated Check a a a LSD (P=.05) CV Treatment Prob(F) * * * **, *, # significant at P = 0.01, 0.05, and 0.1 levels, respectively. Darin Gibson and Donovan Fehr, Gaia Consulting Ltd

26 Skin (1 mm) Cortex (1-2 mm) Foliar Application 2 Confine applications 3 Confine applications Medulla (2 mm) Gefu Wang-Pruski, Dalhousie, NS Post-Harvest Application

27 Summary of best approach for phosphite application: Seed Treatment effective at killing spores on seed surfaces but PHYTOTOXIC effects on the developing plants not an option In-Furrow lack of efficacy in a number of trials May also expose cut seed to the product leading to adverse effects

28 Summary of best approach for phosphite application: Foliar Start early! (especially before late blight is found) Control of oomycetes Stimulates plant health and management of other pathogens Need sufficient dose to get disease control (season total of 7-10 L/ac [min. about 2 gallons/ac] is reasonable) 3-4 spaced applications Reduce rates as plants age or in times of stress (drought) Watch the weather to avoid wash-off Risk to seed fields - Still cautious about fields destined for seed (more research is needed on quantity of phosphite in plant tissue that may cause concern and interactions with other nutrients and environmental and crop factors) Post-Harvest Apply at label rate as soon as possible after harvest Manage water volumes Control of silver scurf a bonus Perhaps some risk to seed (conflicting evidence) best mitigated by strict adherence to label rate

29 Acknowledgments Funding Keystone Potato Producers Association Potato Growers of Alberta PEI Potato Board Syngenta Agriculture and Agri-Food Canada

30 Acknowledgments AAFC Charlottetown Rick Peters Bennett Crane Anne MacPhail Kathy Drake Dorothy Gregory Michelle Trenholm Harrington Farm Staff Prince Edward Island Brian Beaton Marleen Clark Alberta Larry Kawchuk Michael Harding Manitoba Tracy Shinners-Carnelley Susan Ainsworth Vikram Bisht Participating Potato Growers and Associations Provincial Government Reps & Diagnostic Clinics Industry Reps

31 Thank you! For more information: Contact Rick Peters: Web site: