Sydney NSW, Australia
For your information


ProMED-mail is a program of the

Source: Leadership [summ. Mod.DHA, edited]

Potato farmers in Plateau state have suffered great losses due the destruction of their crops by late blight. They called on the state government to urgently look into the problem. Many hectares potato crops have been lost to the deadly blight over the years.

Virtually all potato farms in Plateau North and Central have been destroyed this 2022 cropping season. The losses will also have a negative effect on yields of other crops, because farmers buy fertiliser for these with the money they make from potato sales.

[byline: Achor Abimaje]
communicated by:

[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 and 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. In Europe, regional differences in pathogen population diversity no longer exist; increasingly virulent strains have been reported to emerge mainly on potato (see previous ProMED posts in the archives), but recently also on tomato (ProMED post 20180611.5850443).

In Nigeria, PLB has been present since at least 1978, but its severity was reported to have increased dramatically from around 2012. In 2018, a survey was conducted to determine the local pathogen population. The investigation identified _P. infestans_ strain 33_A2 for the 1st time in Nigeria and on the African continent (ProMED post 20200103.6868372), with all locally grown crop cultivars showing susceptibility. Previously, this strain had been found to have been imported with seed potatoes to India (ProMED-mail post 20180418.5755980). This suggests the introduction of 33_A2 to Africa in the same way and stresses yet again the importance of reliable national biosecurity diagnostic and certification systems.

Nigeria: and,616
Nigerian states:
Africa, overview:

Late blight on potato:,,, and (resistant vs. susceptible cultivars)
Late blight on tomato:
Microscopy of PLB infected cells:

Information on late blight: (with photo gallery),,,,,mgmt-late-blight-potatoes.html, and
First report of PLB 33_A2 in Nigeria:
_P. infestans_ taxonomy & synonyms: and
Global Initiative on Late Blight:
- Mod.DHA]


No responses yet...