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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

The epidemic started on 22 May in a field that was flooded 10 days previously. As weather conditions were very favorable at the end of May and, especially, at the beginning of June, blight could spread very fast. This wet period was followed by hot and dry weather until the end of June, which reduced the speed of the epidemic. During July the infection pressure was low to moderate (rain in the first part of July) and the beginning of August was again very wet. The western and central parts of Switzerland were more affected than the eastern part, but in the eastern part late blight was recorded already in June, compared to July in 2001.

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

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

Data for 20022

5–6 fungicide treatments were carried out (mean value of 141 PhytoPRE participants). On average they used 2 sprays with a contact fungicide and 3 sprays with a translaminar fungicide. Systemic fungicides are rarely recommended; therefore hardly any sprays (0.3) with such a fungicide were recorded.

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

Data for 20022

PhytoPRE, an internet-based [www.phytopre.ch] information and decision support system (DSS), has been validated and implemented. Warnings are sent to growers based on weather information, cultivar resistance and history of fungicide applications.

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

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

The A2 mating type of P. infestans found out of Mexico for the first time, isolated from potato in two locations in Switzerland (Hohl & Usken, 1984).

The frequency of A2 was 4% in both 1990 (n = 134) and 1994 (n = 166) (Gisi et al, 1995).

104 isolates of P. infestans from 61 potato fields were tested for virulence. 11 physiological races/pathotypes were identified: 4.10.11 (1%); 1.3.4.7 (1%); 1.3.4.7.11 (2%) and 1.3.4.10.11 (1%). The remaining seven pathotypes (making up 95% of the isolates tested) had 6–8 virulence genes, including all known R genes except 9. Pathotype 1.3.4.7.10.11 was present at 65% (Gisi et al, 1995).

The proportion of oxadixyl resistant isolates was about 50% (1988–1990) with 50% sensitive. During 1992–1994, about 70% of the isolates tested were resistant and 10–20% were intermediate (Gisi et al, 1995).

7. Disease risks and/or major needs?

8. Any publications on late blight in the country?  

Forrer H R, Gujer H U and Fried P M. 1993. Phytopre: A comprehensive information and decision support system for late blight in potatoes. pp. 173–181 in: Secher B J M, Rossi V and Battilani P (eds), Proceedings of the workshop on computer based DSS on crop protection, 23—26 November, Parma, Italy. Commission of the European Communities, Danish Institute of Plant and Soil Science, Ministry of Agriculture, Lyngby, Denmark.

Gisi U, Iten F and Ohl L. 1995. Changes in sensitivity to fungicides and epidemiological behaviour of Phytophthora infestans field isolates. pp 142–147 in: Dowley L J, Bannon E, Cooke L R, Keane T and O’Sullivan E (eds), Phytophthora infestans 150, Proceedings of EAPR-Pathology Section, September 1995 Dublin, Ireland. Boole Press, Ltd., Temple Bar in conjunction with Teagasc, Carlow. Ireland.

Gujer H U, Friend P M and Forrer H R. 1995. Prediction of the onset of late blight epidemics. pp 364–365 in: Dowley L J, Bannon E, Cooke L R, Keane T and O’Sullivan E (eds), Phytophthora infestans 150, Proceedings of EAPR-Pathology Section, September 1995 Dublin, Ireland. Boole Press, Ltd., Temple Bar in conjunction with Teagasc, Carlow. Ireland.

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. Resutls 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.

Hohl HR, Iselin K, 1984. Strains of Phytophthora infestans from Switzerland with A2 mating type behaviour. Transactions of the British Mycological Society 83:529–530.

Kleinhenz B and Jörg E. 2000. Results of Validation Trials of Phytophthora DSS in Europe in 1999. pp 180–190 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.

Nuninger, C. Steden, C. Staub, T. 1995. The contribution of metalaxyl-based fungicide mixtures to potato late blight control. pp 122–129 in: Dowley L J, Bannon E, Cooke L R, Keane T and O’Sullivan E (eds), Phytophthora infestans 150, Proceedings of EAPR-Pathology Section, September 1995 Dublin, Ireland. Boole Press, Ltd., Temple Bar in conjuntion with Teagasc, Carlow. Ireland.

Ruckstuhl M and Forrer H R. 1999. Validation of MISP model for the control of potato late blight by means of sporangial movement and leaf disease assessment. pp 155–163 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-Special Report no. 5. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Steenblock T, Forrer H R and Fried P M. 2002. www.phytopre.ch: the internet based decision support system (DSS) PhytoPRE+2000 to control late blight on potatoes in Switzerland. pp 183–192 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.

Steenblock T and Forrer H R. 2001. Developing PhytoPRE + 2000: An Internet based information system for late blight control in Switzerland. pp 271–284 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.

Steenblock T, Ruckstuhl M and Forrer H R. 2000. Validation of the MISP model for the control of potato late blight in Switzerland form 1996 to 1999. pp 222–234 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.

9. Is tuber blight an increasing problem?

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 Switzerland provided by T. Musa-Steenblock.