Optimizing the use of curative fungicides

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2 James Hutton Institute, 3 University of Edinburgh Leading the

1 Optimizing the use of curative fungicides Kyran Maloney 1, Neil Havis 1, David Cooke 2, Gary Loake 3, & Ruairidh Bain 1 1 SRUC, 2 James Hutton Institute, 3 University of Edinburgh Leading the way in Agriculture and Rural Research, Education and Consulting

2 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Preliminary conclusions Future plans

3 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Preliminary conclusions Future plans

Aim: produce a simple decision aid to support growers.

4 Introduction Curative fungicides active after infection, but before symptoms. Increasingly used in spray programs. Aim: produce a simple decision aid to support growers. Start point: Hutton Criteria. End point: curative effect lost.

5 Scottish fungicide use: modes of action * *Data collated from SASA, Pesticide Usage in Scotland surveys

6 Scottish fungicide use: actives with curative rating* *Data collated from SASA, Pesticide Usage in Scotland surveys

7 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Preliminary conclusions Future plans

General approach Experiments use fungicide

8 General approach Experiments use fungicide with good curative rating: fluopicolide + propamocarb Full label dose (1.6 L / ha) Used pathogen isolates from current GB lineages. Used important varieties Different foliar blight resistances. Logged and / or controlled temperature.

9 Components of research Field Trials Data for decision aid Quantify pre-symptomatic biomass via qpcr Controlled bioassays Temperature data & growth models

10 Components of decision aid Previous fungicide Decision aid for growers P. infestans genotype Cultivar foliar resistance rating Temperature (data & growth models)

11 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Preliminary conclusions Future plans

Procedure: Artificially inoculated plants, leaves or discs.

12 Controlled bioassays Purpose: Explore how curative control changes as pathogen develops. Data used in decision aid. Procedure: Artificially inoculated plants, leaves or discs. Incubated. Samples treated 4 hours intervals. Returned to incubator. Symptoms assessed.

13 Disc infection in relation to delay in application of fungicide Isolate: 10290A Genotype: 7_A1 yy = ee (xx ) R 2 = 0.78 (p < 0.01)

14 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Preliminary conclusions Future plans

15 Field trials Several field trials: Staggered inoculations and/or curative spray times. Use of different varieties. Temperature logged. Use separate trials to build and later validate decision aid.

Start point of decision aid Variety Resistance Rating King Edward 3 Cara

16 Small plants field trial Small plants grown, range of resistances. Exposed to natural inoculum in high risk conditions. Start point of decision aid Variety Resistance Rating King Edward 3 Cara 5 Sarpo Mira 7 Plants treated curatively. Plants then incubated and assessed for presence of lesions.

17 Cultivar resistance & curative fungicide treatment Disease development time: 43 hours lesion count (log transformed): Treatment: F = 17.98, df = 1, p < 0.01 Cultivar : F = 32.33, df = 2, p < 0.01 T*C: F = 3.36, df = 2, p = 0.05

18 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Preliminary conclusions Future plans

Thermal time (or similar). Currently collecting data for parameters.

19 Temperature Very important factor: Affects pathogen growth. Known to modify curative window. Rates of development included in aid. Thermal time (or similar). Currently collecting data for parameters. Example Temperature Function Developmental min = 10 o C Developmental max = 30 o C Optimum = 20 o C

20 Pathogen development Use qpcr to quantify P. infestans DNA. Explore pre-symptomatic development. Frozen samples from latent period. Collected across experiments with different modifying factors.

21 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Preliminary conclusions Future plans

Quantitative resistance extends curative window on tested

22 Preliminary conclusions On susceptible cultivars, curative control rapidly declines hrs post infection. Quantitative resistance extends curative window on tested cultivars. Temperature and biomass data will allow comparisons between experiments.

23 Presentation overview Introduction Structure of the project Experimental work Bioassays Field trials Modifying factors Conclusions so far Future plans

24 Current / future work More repeats of controlled bioassays. Include more cultivars with range of resistances. Finalise temperature model. Field trials 2017 explore role of previous fungicide application. Assemble decision aid!

References + Acknowledgments References Nielsen, B.J., and Bødker, L. (2002). Field Experiments with preventive and curative control of potato late blight. PPO-Spec. Rep. 8, 211. Bugiani, R.

25 References + Acknowledgments References Nielsen, B.J., and Bødker, L. (2002). Field Experiments with preventive and curative control of potato late blight. PPO-Spec. Rep. 8, 211. Bugiani, R., Antoniacci, L., and Trevisan, I. (2010). Curative effect of fungicides against tomato late blight. In Schepers HTAM, Ed. Proceedings of the Twelfth EuroBlight Workshop. PPO Special Report No. 14, pp Genet, J., Jaworska, G., Geddens, R., Shepherd, C., and Bain, R. (2001). Effect of temperature on the curative and Anti-sporulant action of cymoxanil for control of Phytophthora infestans. In: Westerdijk, C.E., and Schepers, H.T.A.M, Eds. Proceedings of the fifth workshop on the European network for development of an integrated control strategy of potato late blight. PAV-Special Report no. 7, Lees, A.K., Sullivan, L., Lynott, J.S., and Cullen, D.W. (2012). Development of a quantitative real-time PCR assay for Phytophthora infestans and its applicability to leaf, tuber and soil samples. Plant Pathol. 61, Acknowledgements This work is funded by an AHDB Potatoes PhD studentship. Many thanks to staff at JHI for provision of P. infestans isolates, and to SRUC staff at both Edinburgh and Auchincruive sites for assistance with designing and conducting experiments.

26 Leading the way in Agriculture and Rural Research, Education and Consulting

Strategies for integrated deployment of host resistance and fungicides to sustain effective blight control

Strategies for integrated deployment of host resistance and fungicides to sustain effective blight control Alison Lees, David Cooke, Peter Skelsey James Hutton Institute Faye Ritchie, Aldwyn Clarke, Neil