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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

LB was first reported in plastic covered potatoes on 29 May, a week earlier than in 2001. The first report of late blight in uncovered fields was at 26 June. During the first half of July, late blight was found in most potato districts as far north as to Trøndelag. Warm weather with some wet periods resulted in a high infection pressure early in the season affecting early crops. The disease pressure was very high in some districts during the summer, especially in Hedmark (inland counties).

The disease sources are mainly seed potatoes. Some private gardens with heavy infections of potato late blight may cause infection pressure for commercial production. Oospores as infection source are possible in some situations.

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

In conventional crops late blight normally do not cause yield losses. However on organic farmers the foliar damage normally cause yield losses. Tuber blight might occur, but most cultivars used have high level of tuber blight resistance.

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

Early crops are often unsprayed, or only 1-2 sprays are applied before harvest. The main crops are sprayed 6–-8 times in some regions. In regions with short growing season and low disease pressure 2- 4 sprays are more common. The main fungicide is Shirlan, while Tattoo is used 1 – 2 times during the season. Other fungicides used are Dithane, Acrobat and occasionally Epok.

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

The majority of the main crops are cultivars with medium level of foliar and tuber resistance.

Data for 2002²

The local advisory services in the most important potato areas looked for the first symptoms of late blight. Unsprayed fields were inspected every week. All early findings of late blight were reported in Web-Blight, and were available on the Internet with easy access from the forecast system, VIPS (www.vips-landbruk.no)/. Other elements in VIPS are forecasts based on Førsund rules and Negative prognoses. In these models weather prognoses from The Norwegian Meteorological Institute and historical data from meteorological stations owned by The Norwegian Crop Research Institute, are used.

Since February 21, 2003, Web-blight, an international web-based information and decision support system for potato late blight is bringing day-to-day information on the first occurrences and the development of late blight in Denmark, Norway, Sweden, Finland, Estonia, Latvia, Lithuania and Poland (http://www.web-blight.net)

Resistant potato varieties cultivated: Beate, Peik, Troll.

Source: Global Catalog of Late Blight Resistant Varieties: www.cipotato.org/gilb/Gilb_catalog/principal.htm

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

Resistance to the fungicide Epok has been reported.

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

Both mating types are present, and the proportion of A2 is high at several locations. Most isolates have 4 or more virulence factors. The most common race is 1.3.4.7.10.11. Resistance to metalaxyl is common.

7. Disease risks and/or major needs?

8. Any publications on late blight in the country?  

Bergjord A K and Hermansen A. 2001. Mating types and metalaxyl resistance among isolates of Phytophthora infestans collected during different periods of the growing season. pp 219–232 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, Lellystad, Netherlands.

Bjor, T. Mulelid, K. 1991. Differential resistance to tuber late blight in potato cultivars without R-genes. Potato Research 34:3–8.

Bjor, T. 1987. Testing the resistance of potato genotypes to tuber late blight. Potato Research 30:525–532.

Brurberg, M.B., A. Hannukkala and A. Hermansen. 1999. Genetic variability of Phytophthora infestans in Norway and Finland as revealed by mating type and fingerprint probe RG57. Mycological Research 103(12): 1609-1615.

Dahlberg, J.  Andersson, B. Nordskog, B. & Hermansen, A. 2002. Field survey of oospore formation by Phytophthora infestans. pp 134 in: Lizárraga C (ed), Late blight: Managing the global threat. Proceedings of the Global Initiative on Late Blight Conference, Hamburg, Germany, 11–13 July 2002. International Potato Center, Lima, Peru.

Forsund, E. 1983 Late blight forecasting in Norway 1957–1980. EPPO Bull. 1983. 13(2):255–258.

Forsund, E. Flaatten, H.K. 1958 Experiments of forecasting late blight epiphytotics in Norway. European Potato Journal 1:5–13.

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.

Hansen, J.G., Andersson, B. & Hermansen, A. 1995. NEGFRY – A system for scheduling chemical control of late blight in potatoes. pp 201–208 in: Dowley L J, Bannon E, Cooke L R, Keane T and O’Sullivan E (eds), Phytopthora infestans 150, Proceedings of EAPR-Pathology Section, September 1995 Dublin, Ireland. Boole Press, Ltd., Temple Bar in conjunction with Teagasc, Carlow. Ireland.

Hermansen A, Nordskog and Brurberg M B. 2002. Studies on formation and survival of oospores of Phytophthora infestans in Norway. pp 77–80 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.

Hermansen, A. Hannukkala, A. Hafskjold Naerstad, R. & Brurberg, M.B. 2000. Variation in populations of Phytophthora infestans in Finland and Norway: mating type, metalaxyl resistance and virulence phenotype. Plant Pathology 49:11–22.

Hermansen A, Naerstad R H, Admussen T and Bruberg M-B. 2000. Status of late blight in Norway: Population and control strategies. pp 241–252 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.

Hermansen A, Hannukkala A and Hafskjold R. 1998. Population studies of Phytophthora infestans in Finland and Norway. pp 208–217 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-Special Report no. 3. Applied Research for Arable Farming and Field Production of Vegetables, Lelystad, Netherlands.

Hermansen A and Amundsen T. 1997. Late blight warning in Norway. pp 79–84 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.

Nærstad, R.E.H. 2002. Exploitation of cultivar resistance in potato late blight disease management and some aspects of variation in Phytophthora infestans. Doctor Scientiarum Theses 2002:21, Agricultural University of Norway, ISBN 82-575-0504-8  

9. Is tuber blight an increasing problem?

Tuber blight is not a big problem since most cultivars used have medium to high level of tuber resistance. Tuber blight is mainly a problem in home gardens.

Contact: Arne Hermansen, The Norwegian Crop Research Institute, Plant Protection Centre, Department of Plant Pathology, Høgskoleveien 7, Norway.  Email: arne.hermansen(at)PLANTEFORSK.N

[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 Norway provided by B. Nordskog.