.

Date: January 3, 2008
Source: The Daily Star [edited]
<http://www.thedailystar.net/story.php?nid=17606>

Vast areas of potato fields in Nilphamari are attacked with early blight and late blight diseases due to dense fog and chilly cold.
With expectations of good prices from potato as in last year [2007], farmers deployed all their resources to have a good yield, but the prospects have dashed their hopes.

During visits to potato fields in Itakhola, Tupamari and Ramnagar villages in Sadar upazila [sub-district]; Balagram and Golna in Jaldhaka; Kalikapur, Nitai and Bahagli in Kishoreganj and Gayabari and Khalisha-chapani in Dimla, potato plants in many fields were seen dying with their stems rotten and leaves shrunk. Farmer Hasanul Islam in Tupamari village in Sadar upazila said he sowed potato on 4 bighas
[0.54 ha] of land. Plants on one bigha [0.13 ha] are dying due to attack by the diseases. Adjoining fields will also be attacked soon, he said. Tayeb Ali of Monthena village in Kishoreganj said his 2 bighas [0.26 ha] of potato have already been attacked with stem rot disease. The plants are dying rapidly. They said the diseases spread rapidly from one field to another.

Farmers in most affected areas alleged that despite repeated appeals, block supervisors seldom visit their affected potato fields to give proper advice on how to protect the crop. When contacted, a block supervisor seeking anonymity said he is under pressure from higher authorities to oversee fertilizer distribution.

Deputy Director of District Agriculture office, Eunus Ali, said early blight and late blight diseases may attack potato fields when the temperature drops to 8 C and the weather remains damp for days due to dense fog. However, he said he did not get any report of attack by early blight or late blight diseases in potato fields. "If there is any attack, it would be negligible."

Crop specialist of the Agriculture Extension Department (AED) in Nilphamari, Osman Gani, said fungicide can be sprayed in fields as a precaution against the diseases if damp weather continues for over one week. AED sources said the target of potato cultivation in the district was 16 000 hectares. But enthusiastic farmers who got high prices last year [2007] exceeded the target. Potato has been sown on a record 22 000 hectares this year [2008], they said.

--
Communicated by:
ProMED-mail <promed@promedmail.org>

[There are 2 major leaf blights of potato.

Early blight

Early blight is caused by the fungus _Alternaria solani_. Symptoms of dark spots usually develop 1st on the older leaflets of mature plants, spreading to the younger leaves under favorable weather conditions. Spots enlarge causing early senescence of leaflets and yield reduction. The fungus may also cause lesions on tubers. This pathogen can often be recovered from healthy-looking leaf tissue prior to the onset of tubers but causes no visible symptoms until potatoes approach maturity. The disease occurs over a wider range of climatic conditions than late blight (see below). The fungus is spread with infected plant material (including tubers), by mechanical means, and by wind and rain. Most rapid progress of the disease occurs during periods of alternating wet and dry weather. Early blight is often more severe when the potato crop has been under stress of poor nutrition, injury, insect damage, drought, or other types of stress.
Cultivars with reduced susceptibility are available, and fungicides are used for disease management.

Late blight

Late blight is caused by the fungus _Phytophthora infestans_, which can also infect other solanaceous crops such as tomato or eggplant.
It is one of the most important potato diseases worldwide with reported yield losses of up to 75 percent. It affects leaves as well as tubers and is favoured by cool, moist conditions. The fungus is spread by plant material (including seed tubers), wind and water, and solanaceous weeds can serve as pathogen reservoirs. Other fungi and bacteria often invade blight-infected tubers resulting in total tuber breakdown. Late blight is a concern in many countries because new and even more virulent strains continue to emerge. Some of these can destroy a potato plant in a matter of hours and a complete crop within days. Disease management includes preventative fungicide treatments of seed tubers as well as fungicide sprays of crops.

Stem rot

The 3rd disease mentioned above, stem rot (also called white mold), is caused by the fungus _Sclerotinia sclerotiorum_. This soil-borne fungus is among the most nonspecific, omnivorous and successful of plant pathogens and is present worldwide in a wide range of climates.
Almost 400 host species are known, including crops such as cabbage, common bean, citrus, celery, coriander, melon, squash, soybean, tomato, lettuce, and cucumber. Symptoms on potato include rapid wilting and death of vines leading to yield losses of varying severity. The fungus can survive in soil as hard black sclerotia and is also spread by infected plant material. Disease management includes cultural practices and fungicide applications.

Different perceptions of the seriousness of agricultural problems by politicians and farmers appear to occur repeatedly in Bangladesh (see previous ProMED post no. 20071030.3524 on rice diseases in this country). There is no doubt that the farmers are facing serious hardship, however, the national system to respond to crop disease outbreaks appears to be lacking.

Maps
Bangladesh:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/bangladesh_pol96.jpg>  and <http://healthmap.org/promed?v=23.8,90.3,5>
Districts and cities:
<http://www.mapsofworld.com/bangladesh/bangladesh-political-map.html>
Upazilas:
<http://en.wikipedia.org/wiki/Upazila>

Pictures:
Early blight lesions on potato leaf:
<http://www.ag.ndsu.edu/pubs/plantsci/hortcrop/pp1084-4.gif>
Potato late blight, tuber symptoms:
<http://www.sciencedaily.com/images/2007/01/070102132649.jpg>
Potato late blight, leaf symptoms:
<http://www-biol.paisley.ac.uk/bioref/Chromista/potato_blight.jpg>
Potato stem rot symptoms:
<http://ipmnet.org/plant-disease/image.cfm?RecordID=307>

Links
Description of potato late and early leaf blights:
<http://www.ag.ndsu.edu/pubs/plantsci/hortcrop/pp1084w.htm>
Late blight information, history, and background:
<http://www.apsnet.org/online/feature/lateblit/>,  and <http://www.olympusmicro.com/micd/galleries/brightfield/potatoblight.html>
Management of potato diseases including early and late blights:
<http://archives.eppo.org/EPPOStandards/PP2_GPP/pp2-02-e.doc>
Late blight information and resources via:
<http://www.potato.org.uk/department/knowledge_transfer/fight_against_blight/advice_blight.html>
_A. solani_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=444460>
_P. infestans_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=232148>
Information on stem rot of potato:
<http://ipmnet.org/plant-disease/disease.cfm?RecordID=911>
Information on _S. sclerotiorum_:
<http://www.extento.hawaii.edu/kbase/Crop/Type/s_scler.htm>  and <http://www.cals.ncsu.edu/course/pp728/Sclerotinia/S_sclerotiorum.html>
_S. sclerotiorum_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=212553>
AED:
<http://www.dae.gov.bd/>
- Mod.DHA]

[see also in the archive:
2007
----
Late blight, potato - India (02): (Punjab, W Bengal) 20071221.4099 Late blight, potato - UK: new strains 20071207.3939 Late blight, potato - India: (Punjab), alert 20071116.3715 Fungal diseases, vegetable crops - Canada: cucumber, potato 20070730.2442 Late blight, potato & vegetable fungal diseases - Europe 20070708.2174 Late blight, potato - India, UK 20070509.1491
2006
----
Late blight, potato - India (Kashmir) 20060424.1200 Late blight, potato - USA (AK), Bangladesh 20060324.0911
2003
----
Late blight, potato - Papua New Guinea 20030306.0554
2002
----
Potato late blight, potato - Canada (Newfoundland) 20020818.5091
2001
----
Sclerotinia shoot blight, grapevine - Chile 20011103.2724 Phytophthora infestans, potato late blight - Russia 20010620.1177 2000
----
Potato late blight, global research efforts 20001031.1903 Potato late blight: global initiative 20000516.0765
1996
----
Potato late blight: global threat 19960617.1123]

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