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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)?

Potato is one of the most important cash crops. The production is mainly for the fresh market. Late blight is the main limiting factor in the highlands

Due to year-round cultivation of potato and other solanaceaous crops, the pathogen can easily survive. Un-harvested tubers also act as a source of inoculum. 

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

Losses can range from 10–15% in the hilly areas of Nuwara Eliya and Welimada

Most farmers spend from US$ 200 to 300 per ha to control the disease.

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

Most farmers use fungicides regularly with 12–15 sprays in the wet season and six to eight in the dry season. Knapsack sprayers, (power or hand operated) are used

Recommended fungicides to control LB (K P Somachandra,Regional Agricultural Research and Development Centre, 2000, report for GILB South and West Asia Linkage Group) 

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

The two resistant varieties, Sita and Krushi, were released for cultivation about 15 years ago. However, these varieties are unpopular because they have a 4 1/2 month vegetative period and seed is unavailable.

Late blight resistance screening of tuber families from CIP resulted in the selection of lines 241, 245 and 246, originating from the CIP 34-8 progeny, which have remained resistant under both heavy rainfall and drier weather conditions.

Cultural practices such as high ridging, destruction of infected crop residues, crop rotation, use of healthy seed materials and avoidance of staggered cultivation are also used.

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

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

The P. infestans population is mainly A1 — the A2 mating type has been found only on imported seed of potato cultivars Maranka and Agria in one location.

According to two surveys conducted in the highlands, the P. infestans physiological races have increased in complexity from one to five avirulence genes in 1996 to four to eight in 1998. In Rahangala, a physiological race with nine avirulence genes was found in 1996 and in 1998 all 11 known avirulence genes were detected. 

7. Disease risks and/or major needs?

8. Any publications on late blight in the country?  

GILB Annual Report 2000. 2001. pp 7–9 GILB Linkage Groups, Southwest Asia. International Potato Center (CIP), Lima, Peru.

Katsube T, de Vaz C R. 1976. Races of Phytophthora infestans in Sri Lanka. Annals Phytopathological Society of Japan 43:590-592

9. Is tuber blight an increasing problem?

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