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1. Late blight occurrence and LB severity by major production area in the country. What crops were affected (tomato, potato, others)? Disease sources (seed, cull piles, volunteer plants, soil)? 

Data for 2002²

Late blight occurs on potato and tomato.

On the north-western coasts of Brittany, polythene covered crops suffered the first blight outbreak as early as 10 April. Weather conditions remained very favorable for blight dispersal during April, requiring first fungicide treatments when the polythene was removed. During May, wet conditions favoured blight dispersal, but cold temperatures kept blight pressure low. At harvest, from the end May to mid June, the disease pressure increased with increased temperatures. Early harvested crops escaped tuber blight, but the other remaining crops with infected foliage created inoculum for just emerging ware and seed potato crops in inland Brittany.

Early crops in the north-eastern coast (Saint Malo) escaped blight contamination until harvest in June.

In the north of France, crops were planted 3 weeks earlier than in 2001. Blight was first observed on a dump (15 May), this coincided with the second generation of blight in the DSS. In Ardenne Champagne, blight was first seen in the end of May. In the beginning of June the infection risk increases. The pressure is stronger in Picardy, in Pas-de-Calais, North and Champagne Ardennes. The pressure is lower in the Central Region. In unprotected fields the first symptoms on leaves and stems are seen from 20 June onwards. High temperatures in June decrease the infection pressure, but in July infection pressure again increases. Blight can be found on the edges of most fields in the north of France and Picardy. Infection pressure remains high due to regular rainstorms (20–30 mm). In the beginning of August conditions are dry, but later in August rainstorms again increase the infection pressure in the North and in Picardy. The sporulation potential calculated by the model MILSOL remained very high during the whole of the growing season.

2. LB impact (foliar damage, yield losses, tuber rot occurrences)?

Data for 2002²

In Brittany (north-western France), organic crops planted mid April, escaped major blight pressure. Susceptible cultivars were effectively protected with 4–6 copper-based treatments. In the north of France, many organic fields were 100% destroyed from the end of July. Problems with tuber blight were not recorded. 

In Brittany the incidence of tuber blight was rather low irrespective of production type (early, organic, ware, seed), possibly explained by the use of a fungicide treatment at haulm killing and a new effective desiccant. In the north of France the organic fields were completely destroyed.

3. Fungicide use (amounts, types, etc.)?

Data for 2002²

For early production in Brittany, the number of treatments ranged from 8–12 according to local conditions. Contact fungicides were favored when there was a low blight pressure. Cymoxanil and other translaminar products were applied during high blight pressure. In the north of France, Pas-de-Calais area and Picardy, 12–13 sprays were needed to control blight. In the Ardennes Champagne region, 8–10 sprays were needed. On susceptible varieties, the first spray was on 1 June on other varieties on 8 June. Systemic fungicides provided a protection of new growth during the active growth period. The use of rain-fast fungicides provided a better protection of the foliage and allowed a reduction in the number of treatments. Products containing cymoxanil were used when blight was observed in the field. Fluazinam and cyazofamid are recommended to prevent tuber blight.

4. Other LB control measures (resistant cultivars, forecast systems, none)?

Phytophthora Decision Support Systems (DSSs) validated in different European countries, including France (Hansen et al, 2002). Two epidemiological models , MILSOL and GUNTZ-DIVOUX have been tested in northern France to predict risk periods (Duvauchelle & Dubois, 2000a).

5. LB control effectiveness (fungicide or host resistance failures)? 

6. Pathogen strains (mating type, fungicide resistance, virulence factors, etc)?

The A2 mating type was first detected on tomato in 1995 (Lebreton et al, 1996) and on potato in 1996. (Lebreton et al, 1998).

In Brittany 14 physiological races/pathotypes were detected in 1992, 11 in 1993, 16 in 1994, 15 in 1995 and 15 in 1996 among 38, 47, 48, 52 and 48 isolates, respectively. In northern France, 13 physiological races were found among 38 isolates in 1995 and 10 were found among 48 isolates in 1996 (Lebreton et al, 1998).

Isolates collected in 1996 from northern France and Brittany were predominantly A1 and susceptible to metalaxyl at 92% and 65%, respectively. (Lebreton et al, 1998).

In a study in northern France, 1997–1999, (Emery et al, 2000), the proportion of metalaxyl resistant isolates increased from 10.2% in 1997, 18% in 1998 to 32.3% in 1999. In 1997 4.4% (11 isolates) of the population tested were A2, most from tomato or potato in home gardens. In 1998 only one A2 isolate was detected. It was from tomato in a home garden.

7. Disease risks and/or major needs?

8. Any publications on late blight in the country?  

Andrivon, D. 1994. Races of Phytophthora infestans in France, 1991-1993. Potato Research 37:279–286.

Andrivon D, Lebreton L, Laurent C, Duvauchelle S, 1998. Phytophthora infestans: changing populations. Phytoma, No. 502:28–30.

Andrivon D, Beasse C and Laurent C. 1994. Characterization of isolates of Phytophthora infestans collected in northwestern France from 1988 to 1992. Plant Pathology 43:471–478.

Dubois L, Duvauchelle S and Pinchon V. 1998. Integrated control trial against mildew in potatoes using resistant cultivars and the models MILSOL and GUNTZ-DIVOUX. pp 63–64 in: First transnational workshop on biological, integrated and rational control: status and perspectives with regard to regional and European experiences, 21–23 January 1998, Lille, France.

Duvauchelle S. 1999. Attempt of perfecting an integrated control in the potato production. pp 142–154 in: Schepers H and Bouma E (eds), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 9–13 September 1998, Uppsala, Sweden, PAV-Report no. 5. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Duvauchelle S and Dubois L. 2001. The evolution of the foliar late blight resistance of the cultivar – Two years of trials in northern France (1999–2000) — The main results. pp 239–244 in: Westerdijk K and Schepers H T A M (eds), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 6–10 September 2000, Munich, Germany, PAV-Special Report no. 7. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Duvauchelle S and Dubois L. 2000a. Supervising the control against the potato late blight using model MILSOL combined with the varietal resistance: a synthesis of 5 trials carried out in northern France. pp 108–116 in: Schepers H (ed), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 29 September – 2 October 1999, Oostende, Belgium, PAV-Report no. 6. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Duvauchelle S and Dubois L. 2000b. Investigation on the varietal resistance. pp 276–279 in: Schepers H (ed), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 29 September – 2 October 1999, Oostende, Belgium, PAV-Report no. 6. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Duvauchelle S and Dubois L. 1999. The epidemic development of Phytophthora infestans in northern France in 1998. pp 256–257 in: Schepers H and Bouma E (eds), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 9–13 September 1998, Uppsala, Sweden, PAV-Report no. 5. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Duvauchelle S and Dubois L. 1998. Epidemic development of Phytophthora on ware potatoes production in northern France. pp 203–207 in: Schepers H and Bouma E (eds), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 24–27 September 1997, Carlow Ireland, PAV-Report no. 3. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Duvauchelle S and Dubois L. 1997. Models used in France in the warning systems. pp 135–147 in: Bouma E and Schepers H T A M (eds), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 30 September – 3 October 1996, Lelystad, The Netherlands, PAV-Report no. 1. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Emery D, Dubois L and Duvauchelle S. 2000. Status of Phytophthora infestans in northern France since 1997: Mating type, resistance to metalaxyl. pp 280–286 in: Schepers H (ed), Proceedings of the Workshop on the European network for development of an Integrated Control Strategy of potato late blight, 29 September – 2 October 1999, Oostende, Belgium, PAV-Special Report no. 6. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Hansen J G, Kleinhenz B, Jörg E, Wander J G N, Spits H G, Dowley L, Rauscher E, Michelante D, Dubois L and Steenblock T. 2002. Results of validation trials of Phytophthora DSSs in Europe, 2001. pp 231–242 in: Westerdijk C E and Schepers H T A M (eds), Proceedings of the Sixth Workshop of an European Network for development of an Integrated Control Strategy of potato late blight, 26–30, September 2001 , Edinburgh, Scotland, PPO-Special Report no. 8. Applied Plant Research BV, Wageningen, Netherlands.

Lebreton L, Lucas JM, Andrivon D, 1999. Aggressiveness and competitive fitness of Phytophthora infestans isolates collected from potato and tomato in France. Phytopathology, 89:679–686.

Lebreton L, Laurent C, Andrivon D, 1998. Evolution of Phytophthora infestans populations in the two most important potato production areas of France during 1992-96. Plant Pathology, 47:427–439.

Lebreton L and Andrivon, D.1998. French isolates of Phytophthora infestans from potato and tomato differ in phenotype and genotype. European Journal of Plant Pathology 104:583–594.

Lebreton, L. Duvauchelle, S. Andrivon, D. 1996. Occurrence in France and Belgium of A2 mating type isolates of Phytophthora infestans in 1995. pp 262–263 in: Abstracts of conference papers, posters and demonstrations, 13th Triennial Conference of the European Association for Potato Research, 14–19 July 1996, Veldhoven, The Netherlands. Wageningen, The Netherlands.

9. Is tuber blight an increasing problem?

Data for 2002²

In Brittany, the incidence of tuber blight was rather low irrespective of production type (early, organic, ware, seed), possibly explained by the use of a fungicide treatment at haulm killing and a new effective desiccant

In the north of France, many organic fields were 100% destroyed from the end of July. Problems with tuber blight were not recorded.

Comments, additions and corrections are very welcome. Please contact us at GILB(at)cgiar.org

[2] Schepers, H T A M. 2003. The development and control of Phytophthora infestans in Europe in 2002. pp 9–22 in: Westerdijk C E and Schepers H T A M (eds), Proceedings of the Seventh Workshop of an European Network for development of an Integrated Control Strategy of potato late blight, 2–6, October 2002 , Pozan, Poland, PPO-Special Report no. 9. Applied Plant Research BV, Wageningen, Netherlands. Information regarding the late blight epidemic in 2002 in France provided by C. Chatot and L. Dubois.