ProMED 
http://www.promedmail.org

Source: The Indian Express [summ. Mod.DHA, edited]
https://indianexpress.com/article/cities/chandigarh/full-blown-late-blight-attack-damages-potato-crop-punjab-9073844/

Days after the experts from Punjab Agricultural University (PAU) had cautioned farmers against late blight disease in potato crops, a full-blown attack by the disease has affected more than 50% of potato fields. Crops have suffered extensive damage leading to heavy losses, despite some farmers spraying fungicides recommended by PAU. In several districts, potatoes were rotting in the field before farmers could harvest them. Farmers do not expect to be compensated by the government.

PAU scientists cautioned farmers against using unrecommended varieties, as they are highly susceptible to this disease, which could lead to early crop loss. Maintaining proper spacing between plants within the canopy was another key aspect. Adequate spacing promotes better aeration and helps mitigate the risk of late blight development. They suggested the prompt destruction of infected crop residues to prevent spread of the disease to nearby fields. Instead of overhead sprinklers, they encouraged the use of drip irrigation where feasible and emphasised daytime irrigation so that foliage dries before nightfall and the risk of disease development is minimised.

[Byline: Divya Goyal]

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Communicated by:
ProMED

[Late blight of potato (PLB) and tomato is caused by the fungus-like organism (oomycete) _Phytophthora infestans_ and can cause 100% crop loss. The pathogen can also affect some other solanaceous crops. In potato, it affects leaves as well as tubers; in tomato, it causes lesions and rotting of leaves, stems and fruits. The disease is favoured by cool, moist conditions. It can spread rapidly within a crop and destroy it within a few days. Under favourable conditions, epidemics in tomatoes may be even more rapid than in potatoes.

The pathogen is spread by plant material (including potato seed tubers, tomato transplants, plant debris, volunteer crop plants), mechanical means (including human and insect activities), wind and water. Disease management requires an integrated approach; it may include removal of pathogen reservoirs, crop rotation, preventative fungicide treatments of planting material, as well as fungicide sprays of crops. Farm saved or uncertified seed tubers have often been reported as sources of PLB outbreaks. Certified clean planting stock and management strategies for fungicide resistance of the pathogen are considered vital to control late blight outbreaks. Commercial crop cultivars vary in susceptibility to late blight. Development of resistant cultivars is being counteracted by the adaptability of the pathogen.

Late blight is considered an increasing problem worldwide. Considerable variation in aggressiveness between different pathogen strains has been observed, but more virulent strains are emerging frequently. The presence of both A1 and A2 mating types of the pathogen increases the chances of strains with additional fungicide resistances and increased yield losses developing.

Pictures
Late blight on potato:
https://onvegetables.com/wp-content/uploads/2018/08/Potato-late-blight-No-halo.jpg,
https://www.thompson-morgan.com/static-images/tandm/static-articles/how-to-stop-potato-blight/what-is-potato-blight.jpg,
http://farm1.static.flickr.com/81/281344513_74bbffe5fe.jpg and
http://cdn.phys.org/newman/gfx/news/2013/keepingpacew.jpg (resistant vs. susceptible cultivars)
Late blight on tomato:
http://ipm.illinois.edu/ifvn/volume15/images/tomato_late_blight.jpg
Microscopy of PLB infected cells:
http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/brightfield/images/potatoblight.jpg

Links
Information on late blight:
https://gd.eppo.int/taxon/PHYTIN (with photo gallery),
https://doi.org/10.1079/cabicompendium.40970,
https://cropscience.bayer.co.uk/threats/diseases/potato-diseases/late-blight/,
https://cipotato.org/press_room/blogs/combating-late-blight/,
https://www.gov.mb.ca/agriculture/crops/plant-diseases/print,mgmt-late-blight-potatoes.html and
https://www.hutton.ac.uk/research/departments/cell-and-molecular-sciences/epidemiology
_P. infestans_ taxonomy & synonyms:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=232148 and
http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=232148
- Mod.DHA