Problems with resistance in the UK and how to minimise resistance build up

Transcription

1 Problems with resistance in the UK and how to minimise resistance build up Neil Paveley, ADAS Frank van den Bosch & Bart Fraaije, Rothamsted

2 Substrate Product Enzyme Fungicide

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4 Septoria tritici control strobilurins % control Amistar Swift Acanto Vivid

5 Fungicide resistance cases in Europe Years to first detection of resistance (n=67) 12 Number of cases = single-site inhibitors = multi-site inhibitors FDR time (years) Grimmer et al., 214 Pest Management Science

6 Broad-spectrum systemic modes of action Azoles Strobilurins SDHIs (new generation) 197s 199s 21s Next new mode of action?? Pipeline confidentiality? Regulatory uncertainty?

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8 Septoria percent control Azole septoria activity (full label dose) Proline Opus / Ignite Protectant Prothioconazole Epoxiconazole 1 Variance accounted for = 43.2% Curative 1 Variance accounted for = 62.4%

9 12 1 SDHI sensitivity of laboratory mutants (Zymoseptoria tritici) Sensitivities of laboratory mutants (M. graminicola ) Data from Fraaije et al. (211) Mol Pl Path Sensitivity (ug/ml) IPO323 IRE3 B-C137R B-S221P Boscalid Bixafen Isopyrazam B-S221P B-S221P B-S221T B-R265P B-H267F B-H267L B-H267N B-H267Y B-I269V B-P155L/B-H267Y B-S221P/C-R54G B-H267Y/C-H86S B-D166G/D-D129G B-I13V/D-D129E/D-V154A C-L85P C-N86K C-L85P/DV96A D-I127V D-D129E D-D129T Data from Fraaije et al., 211 Molecular Plant Pathology

10 New UK septoria strains Cumulative frequency (%) Cumulative frequency (%) Azole sensitivity C ,1, EC 5 values (μg ml -1 ) A Herefordshire ,1, EC 5 values (μg ml -1 ) B Hampshire 213 Cumulative frequency (%) Cumulative frequency (%) SDHI sensitivity A C ,1,1,1 1 1 EC 5 values (μg ml -1 ) ,1,1,1 EC 5 values (μg ml -1 ) 1 1 B

11 New UK septoria strains Isolate Azole target site (CYP51) mutations SDHI target site mutations Enhanced active fungicide efflux IPO R14-3 L5S, D134G, V136A, I381V & Y461H A L5S, D134G, V136A, I381V & Y461H SdhC A118G Efflux B L5S, V136C, S188N, A379G, I381V, DEL, N513K & S524T C L5S, S188N, A379G, I381V, DEL & N513K SdhC N148S Efflux FRAC reports: SdhC T79N SdhC W8S

12 Selection governed by: Difference in rate of increase of resistant and sensitive strains Exposure time van den Bosch et al., 211 Plant Pathology van den Bosch et al., Ann. Rev. Phytopath.

13 Dose Fungicide programmes Time of spray Time of spray

14 Consequences for fungicide resistance Increase selection No effect Decrease selection Increase dose Increase number of sprays 6 Split the dose 1 1 Add a mixture partner Van den Bosch et al. (214) Annual Review Phytopathology

15 Number of wheat fungicide treatments UK Percent crops treated at each timing T T1 T2 T3 TX 73 Euro J.Nix Euro J.Nix 214 Defra winter wheat disease survey

16 Septoria in fungicide treated crops UK Septoria leaf 2 (%) Defra winter wheat disease survey

17 Value of disease forecasting? Yes Actual epidemic No Predicted epidemic Yes No True positive False negative False positive True negative Te Beest et al., 29 Plant Pathology

18 Consequences for fungicide resistance Increase selection No effect Decrease selection Increase dose Increase number of sprays 6 Split the dose 1 1 Add a mixture partner Van den Bosch et al. (214) Annual Review Phytopathology

19 Selection for tebuconazole insensitive septoria (Field trials) % insensitive (without V136A) P<.1 Untreated Azole full dose Azole full dose SDHI 1/4 dose Azole full dose SDHI full dose

20 Selection for epoxiconazole insensitive septoria (Inoculated glasshouse experiment) Data courtesy of S. Kildea and colleagues

21 Good septoria control and low selection? Septoria resistance risk Risk from higher dose Risk from more sprays Build mixtures from the foundation up: SDHIs Azoles Multisite High Moderate Low - - Minimum SDHI dose & no. of treatments required to achieve effective control Limit no. of azole treatments Robust azole doses at T1/T2 when mixing with SDHIs Maximise use of multi-sites throughout the spray programme

22 Yield and septoria resistance UK wheat varieties Source: HGCA Recommended list of varieties

23 Variety by fungicide programmes 214 T T1 T2 T3 Nil Untreated Untreated Untreated Untreated Low - Azole + Strob + MS Azole + MS - Mod. Mildewicide + Multi-Site (MS) Azole + Strob + MS SDHI + Azole + MS Azole High Azole + Mildewicide + MS SDHI + Azole + Strob + MS SDHI + Azole + MS Azole

24 Variety by fungicide programmes 214 Mean of 4 trials Crusoe Cubanita Conqueror Yield (tonnes/hectare) Untreated Low Moderate High Fungicide programme

25 Variety by fungicide programmes 214 Mean of 4 trials Gross margin ( /ha at 15/tonne) Crusoe Cubanita Conqueror Untreated Low Moderate High Fungicide programme

26 Selection for tebuconazole insensitive septoria Boxworth 214, GS 65 % insensitive (without V136A) LSD = 8.54 P <.1 Variety No. applications Total dose (units of tebuconazole) Susc Res Res 1.25 Res 2.5 Res 2.75 Int 2.75 Susc 2.75 Susc 2 1. Susc Sampled at growth stage 65, ADAS Boxworth 214

27 Conclusions: Pesticide regulation + Resistance = Loss of control Next new broad-spectrum mode of action several years away Treatment decisions determine fungicide resistance Use alternatives to azoles where the target is - septoria protection (solo multi-sites) - or rusts (strobilurin + morpholine). Use mixtures of modes of action effective against septoria. Disease resistant variety + fungicide = mode of action mixture* Variety resistance makes intensity of spray programme less critical * Growing a disease resistant variety does not remove the label requirement to use an effective mixture of fungicide modes of action

28 Thank you! Acknowledgements: Co-authors Research funders Consortium partners Judith Turner, Fera UK Fungicide Resistance Action Group ADAS colleagues