Epidemiology of alien pests in Finnish. agriculture recent case studies. MTT, Agrifood Research Finland

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1 Epidemiology of alien pests in Finnish agriculture recent case studies Asko Hannukkala MTT, Agrifood Research Finland Plant Production Research PKA, Agroecology and Plant Protection in Field Crops

2 Epidemiology of alien pests in Finnish agriculture recent case studies Potato late-blight (Phytophthora infestans) Replacement of an old well established pathogen by new type of population Potato Mop Top Virus (furovirus PMTV) Introduction of a pathogen fit in Nordic climate from neighbouring countries Black leg and soft rot (Erwinia chrysanthemi) Acclimatization of a sub-tropical pathogen to Nordic climate

3 Potato late blight a devastating potato disease

4 Potato late blight First migration in 1840s 1847

5 Potato late blight First migration in 1840s consequences The Irish Famine Onset of mycological research Onset of Plant Pathology Resistance breeding Development of plant protection products End of 1800s 1980s: certain balance between the host and pathogen, effective disease management practises Pathogen: Clonal lineage, only one mating type (sex) A1, no sexual reproduction, limited genetic variation

6 Potato late blight Epidemiology 1840s 1980s Selection towards low or moderate aggressiveness

7 Potato late blight Second world wide migration in 1980s New A1 and A2 mating type population replaced the old clonal A1 population => sexual reproduction 1976? Efter Fry t al, "Historical and Resent Migrations of Chronology, Pathways, and Implications Plant Disease 1993 Vol 77 No 7

8 Potato late blight Second world wide migration in 1980s % of Isolates 100 % Occurrence of A1 a nd A2 27 mating types i n % 80 % 80 % 60 % 60 % 40 % 40 % 20 % 20 % 0 % 0 % DK FIN N SE Mating type A2 A12 A1 A2 A12 A1

9 Potato late blight Sexual reproduction A1 A2 Pathogen independend of host selection towards aggressive strains

10 Potato late blight Second world wide migration - consequences Three earliest blight observations No of days from 1st of July 1,0 80 0,8 60 1= early epidemic 0=late epidemic 0,6 40 0, ,2 0, obs pred

11 Potato late blight Second world wide migration - consequences The Sales average of blight number fungicides of applications for hectares Tattoo Acrobat WG Epok 600 EC Ridomil MZ Shirlan Maneba Dithane

12 Potato Mop Top Virus (furovirus PMTV) TRV PMTV PVY NTN

13 Potato Mop Top Virus (furovirus PMTV) Adapted to cool climate Relatively common in Nordic countries and Scotland Transmitted by powdery scab (Spongospora subterranea) Symptoms developed after cold treatment Year 1975 disaster for domestic potato (seed production) For 1976 lots of imported low quality seed and PMTV Survives in soil for at least ten years inside resting spores of powdery scab In practise infested soil can never be recovered unless potato is not grown for years

14 PMTV and powdery scab Powdery scab

15 PMTV survey ten years after its introduction Starch potato production

16 % o ir e ile v ia m u k u lo ita V E N L A K A R D A L T O M P P A R IK E A B L U E C O N G O B IN T J E R E D S T A R R A P ID O P U I K U L A C O L U M B O L A D Y C L A I R E K U R A S P R E M IE R E L A D Y C R I S T L F O N T A N E B E L L O N A A P P E L L M A T I L D A Aika noston jälkeen mukuloita yhteensä 2 viikkoa viikkoa oireellisia pos. tulos PCR:llä S A V A S A T U R N A V A N G O G H V I C T O R I A L A D Y F E L IC I A P O S M O A S T E R I X V E L O X S E R E S T A H J A N T I M O

17 Fight against Mop Top Zero tolerance in seed production for spraying symptoms Latent infections 15 % of certified seed lots symptomless carriers of the disease Certified seed 2005

18 Black leg and soft rot caused by Erwinia spp. Erwinia carotovora subsp. atroseptica Erwinia carotovora subsp. Carotovora Well established black leg and soft rot pathogens in cool climate

19 Black leg and soft rot caused by Erwinia spp. Similar symptoms caused by Erwinia chrysanthemi in sub-tropical and tropical climate Early 2000s Ech took over in the Netherlands

20 The three species can be distinguished by their DNA-sequences

21 Ech was first found in Finland in 2004 and in 2005 it was relatively common in stems 60 % 50 % 40 % 30 % 20 % 10 % 0 % Eca Ecc Ech

22 And in tubers 60 % 50 % 40 % 30 % 20 % % 0 % 2 Eca Ecc Ech

23 What has happened? we do not know The last few seasons have been warmer than the average, but not sub-tropical Some adaptation in Ech towards cooler climate must have happened What are the consequences? We do not know either Once again we have a new disease to learn to live with It is the challenge for plant protection research and each year we get something new, just to mention pink rot in 2006 that has never before caused any trouble in our climate!

24 Thank you for your attention!