Late blight in 2012 status report

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Harriet Lambert
5 years ago
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Louise Cooke AFBI, Northern Ireland Moray Taylor

1 Late blight in 2012 status report David Cooke Alison Lees Allison Chapman Julie Squires & Louise Sullivan Louise Cooke AFBI, Northern Ireland Moray Taylor Fera Blight scouts, Potato Council, Scottish Government

cf 1034 at same time in 2011) 335 outbreaks to date (183 in 2011) first outbreak Cornwall early

2 2012 summary to date Dry planting but subsequently very wet. Blight active early with extreme disease pressure Many Smith Periods up until July 11 th (5587 cf 1034 at same time in 2011) 335 outbreaks to date (183 in 2011) first outbreak Cornwall early May (cf Fife 28 th June 2011) Herefordshire by 16 th May Scottish Borders 30 th May SSR fingerprinting completed on 55 samples

3 GB P. infestans 2011 population update Isolate no

4 Regional distribution of genotypes England & Wales (n=75) Scotland (n=341)

competition experiments show 13_A2 dominates 6_A1 and others 50 40 30 20 6_A1

5 Average lesion size (mm 2 ) Effect of temperature on different P. infestans genotypes 6_A1 more aggressive than 13_A2 at higher temperatures Field competition experiments show 13_A2 dominates 6_A1 and others _A1 13_A Day Degrees ( C/days)

windows of opportunity for infection than currently realised Recent study also

6 Infection (%) Low temperature infection Approx. 50% of isolates infected at 6 C Not specific to particular genotypes More windows of opportunity for infection than currently realised Recent study also examining interaction of temperature and different time periods at high humidity Temperature ( C)

7 Green33 status (as per Feb 2012) Fluazinam was less effective against a green33 isolate compared to a blue13 isolate in an artificially inoculated field experiment under very high disease pressure and long spray intervals in Lelystad in 2011 The cause (reduced sensitivity, increased aggressiveness...?) not yet known The link between green33 and reduced effectiveness of fluazinam not established and under investigation. Lineage defined by WUR group (Wageningen) where it comprised 20% of popn in SSR profile shared with D. Cooke in October 2011 GB population screened for presence of green33 and only two isolates found. These are from volunteer potatoes in a carrot crop in Norfolk sampled in early October Amongst samples collected during (BayerCropScience & Syngenta) and fingerprinted at JHI green33 was found only in NL Close collaboration between EU scientists allowing good communication and shared findings Kessel, Evenhuis & Schepers (Wageningen UR, NL)

8 Green33 sensitivity testing update A collection of green33, 13_A2 and other isolates have now been tested at Plant Research International (Wageningen, NL) to evaluate the EC50 to fluazinam A wide range of sensitivity to fluazinam exists in the Phytophthora infestans population. For example, all 13_A2 isolates tested were highly sensitive to very low doses. Amongst isolates of green33 some were more sensitive than others; the isolate from the 2011 Dutch field trial was amongst the least sensitive. Trials suggest that, in the absence of fluazinam, green33 is less competitive than 13_A2 and it may have been the higher usage patterns in the Netherlands that resulted in the green33 type becoming established. Green33 is sensitive to all other fungicides. Best practice guidelines should be followed with Shirlan comprising no more than 50% of blight sprays in a season. Mark Bullen (Syngenta) and Kessel, Evenhuis & Schepers (Wageningen UR, NL)

Green33 status (Aug 2012 update) Green33 found in NR21 (Norfolk) in early October 2011 We have focussed on testing samples from the earliest outbreaks in this area and have detected no green33

9 Green33 status (Aug 2012 update) Green33 found in NR21 (Norfolk) in early October 2011 We have focussed on testing samples from the earliest outbreaks in this area and have detected no green33 (33_A2) amongst 50 samples tested to date 2011 NR11 28 Jun 6_A1 NR10 22 Jun 6_A1 NR10 26 Jun 6_A1 & 13_A2 NR10 4 Jul 6_A1 NR29 2 Jul 13_A2 PE20 26 Jun 6_A1 PE20 3 Jul 6_A1 CT7 13 Jun CT7 14 Jun 13_A2 13_A2 Jersey samples (Howard Hinds) 6_A1, 13_A2, 1_A1

10 Oospores The primary inoculum for a few GB outbreaks each year appears to be derived from oospores. Warm wet springs increase the risk of oospore germination. Recent dry/cool springs has decreased the threat in GB Danish industry (Nielsen, Hansen & Bødker, 2011) reported an early and severe start to 2011 blight season that coincided with rainfall events in May & high infection pressure in Late May- June. Ridomil worked well to keep such infection in check. Oospores could still cause problems to the GB industry should weather conditions be suitable early in the season. Long rotations - the best strategy to counter threat of oospores

6_A1 From such recombinants come successful clonal types with traits that make blight more difficult to

11 The oospore threat in other parts of Europe 13_A2 Dominant clonal types plus a collection of diverse novel genotypes - the result of sexual recombination. 6_A1 From such recombinants come successful clonal types with traits that make blight more difficult to manage (e.g. 13_A2, 6_A1 and 33_A2) Nordic populations similarly diverse Geert Kessel, Trudy van den Bosch et al PRI Wageningen Euroblight meeting Russia Oct 2011

Less pathogen diversity in NW Europe (2008-10) 13_A2 still present in many areas (less due to reduced Metalaxyl use?

12 Less pathogen diversity in NW Europe ( ) 13_A2 still present in many areas (less due to reduced Metalaxyl use?) A high proportion of novel misc types particularly in East New clonal genotypes in East and NL Active collaboration among EU scientists helps industry Thanks to Bayer and Syngenta, Howard Hinds, Vangelis Vellios n=350

13 Conclusions Late blight severe in 2012 but robust regimes with a range of active ingredients are enabling effective management P. infestans able to infect below 10 o C but Smith Periods still offer a good indication of disease activity No evidence spread of green33 genotype in early infections in GB. Follow Syngenta best practice advice for Shirlan Population change can be driven by new genotypes that emerge from germinating oospores. Maintain long rotations and manage discard piles and volunteers to minimise all primary inoculum.

14 Ongoing/planned work Completing the isolation and genotyping of GB 2012 samples European and global population diversity in collaboration with industry and other partners Studies on the interaction between pathogen genotype, aggressiveness and response to temperature and humidity for blight outbreak prediction using modified Smith period criteria for improved decision support Longer-term prediction/modeling of epidemic progress of different genotypes to optimise management to minimise emergence of new virulences or fungicide resistance Ongoing testing of pathogen effector diversity for long-term strategies of breeding durable resistance

Changes in epidemiology and population structure of P. infestans in Finland

FOURTEENTH EUROBLIGHT WORKSHOP LIMASSOL CYPRUS 12-15 MAY 2013 153 PPO SPECIAL REPORT NO 16 2014, 153-158 Changes in epidemiology and population structure of P. infestans in Finland 1847-2011 HANNUKKALA