Taro leaf blight, Nigeria

November 2015. A post from the Daily Truth (Nigeria) about cocoyam farming in Katsina province on the border with Niger. Cocoyam farming in Katsina State is gradually being phased out as agricultural research institutes are yet to provide the farmers with a solution to the leaf blighted disease affecting the crop for about 5 years now. In the last two decades, Katsina State, particularly its southern part was a major producer of cocoyam in commercial quantity which is transported to the famous Illela international market in Sokoto, north-eastern states and Niger Republic.

To start with members were confused by the photo and the name cocoyam. The photo in the article is Xanthosoma, but it is a stock photo used by the newspaper, perhaps because cocoyam is a generic name in Africa for taros of all kinds, certainyl Colocasia and Xanthosoma.

Members were concerned that this seems to be an on-going story across West Africa for many years with countries calling for resistant varieties. these already exist in the Pacific, in PNG and Samoa. The truth is something different: the varieties have been sent to West African countries in several years ago, but they are not reaching farmers. There are several reasons for this: (i) there are not the distribution networks available; (ii) farmers prefer the eddoe type of taro and the ones that have been bred for resistant in the Pacific are dasheens, (iii) breeding programmes do not exist to take the Pacific taro and make the hybridisations that are needed.

ProMED has done a note on the disease in Nigeria and that is posted below.

ProMED LEAF BLIGHT TARO _NIGERIA

Date: Wed 18 Nov 2015
Source: Daily Trust [edited]
<http://www.dailytrust.com.ng/news/agriculture/disease-killing-cocoyam-farming-in-katsina/120164.html>Disease killing cocoyam in Katsina
———————————-
Cocoyam [taro] farming in Katsina State is gradually being phased out
as agricultural research institutes are yet to provide the farmers
with a solution to the leaf blight disease affecting the crop for
about 5 years now [see ProMED-mail post
http://promedmail.org/post/20101216.4451]. Katsina, particularly its
southern part, was a major producer of cocoyam which was transported
to the north-eastern states and Niger Republic.

A farmer said, “With the growing devastation of the leaf blight
disease, we can no longer continue with cocoyam farming. We are yet to
find a lasting solution to the leaf blight affecting the crop.” He
stressed the need for agricultural institutions to come up with new
improved seedlings of cocoyam and a reliable solution to the disease.

An agricultural expert and agro-allied product dealer said the disease
can be managed with appropriate systemic or non-systemic fungicides.
“Resistant varieties are the most effective method of controlling the
disease. Symptomatic leaves should be removed to reduce the spread to
the tubers. Cocoyam should be planted in well-draining soils,” he
advised.

[Local] markets are now dominated with potatoes, yam and cereals with
a few bags of cocoyam already affected by the disease.

[Byline: Idris Mahmud]

—
Communicated by:
ProMED-mail
<[email protected]>

[Taro [_Colocasia esculenta_] leaf blight caused by the fungus-like
organism _Phytophthora colocasiae_ was 1st reported in Java in the
early 1900s. Since then, it was found in various parts of Asia and the
Pacific, and in 2010, it was also reported for the 1st time from
Africa (see ProMED-mail post
http://promedmail.org/post/20100715.2365). Both leaves and tubers of
the crop are used, and taro blight results in yield losses of 30-50
per cent or even total crop losses. The disease also reduces the
quality of the harvest.

Symptoms include purple-brown water-soaked lesions on leaves oozing a
clear yellow liquid; lesions enlarge and eventually destroy entire
leaves in 10-20 days, leading to reduced photosynthesis and vigour of
the plant. Disease development and spread are favoured by free water
collecting on older leaves, high temperatures and high humidity. The
pathogen can be spread by wind, splashing rain and mechanical means
(including insects and human activities). Spores survive in plant
material for several weeks, and, therefore, infected planting material
(seed tubers) is a common means of pathogen spread over long distances
and between seasons.

Varying levels of disease intensity in different areas have led to the
suggestion that different strains of _P. colocasiae_ may exist, in
addition to differences in the genetic background of local taro
varieties. Some of these strains appear to be able to infect some
other aroid crops (for example _Alocasia_ species) as well, but
further information is needed on whether non-aroid crops like yam
(_Dioscorea_ species) and cassava (_Manihot esculenta_) could be
affected by these pathogens.

Disease management using an integrated approach has been successful in
the Pacific, including cultural methods (such as crop rotation,
intercropping), fungicides as sprays or treatments for seed tubers,
phytosanitation and use of cultivars with reduced levels of
susceptibility. Programmes specific to different areas for the
assessment of taro blight resistance levels of local cultivars have
been set up by some countries.

In Nigeria, a resistance breeding programme has been established in
2011 by the National Root Crops Research Institute (NRCRI; see
ProMED-mail post http://promedmail.org/post/20110422.1253). However,
breeding of resistant crop varieties, followed by field testing and
eventual multiplication for release to farmers usually takes many
years.

Maps
Nigeria:
<http://worldatlas.com/webimage/countrys/africa/lgcolor/ngcolor.htm>
Nigerian states:
<http://media.premiumtimesng.com/wp-content/files/677x533xnigeria_map_m_104046032.gif.pagespeed.ic.A4Q8ve7feg.png>
Africa (overview):
<http://www.lib.utexas.edu/maps/africa/africa_pol97.jpg>

Pictures
Taro leaf blight symptoms:
<http://staging.pestnet.org/Portals/32/Images/Disease/1067-Taro%20leaf%20blight/1067a-TLB.jpg>,
<http://www.ediblearoids.org/portals/0/taropest/lucidkey/taropest/media/Html/Fungi/Pcolocasiae/Phytophthoracolocasiae20GJ.jpg>
and
<http://www.extento.hawaii.edu/kbase/view/files/pictures/Img0007.jpg>
(compared with healthy leaf)
_P. colocasiae_ zoospores:
<http://www.forestryimages.org/images/768×512/5390071.jpg>

Links
Information on _P. colocasiae_:
<http://www.extento.hawaii.edu/kbase/crop/type/p_coloc.htm> and
<http://www.ediblearoids.org/portals/0/taropest/lucidkey/taropest/media/Html/Fungi/Pcolocasiae/Pcolocasiae3.htm>
Taro leaf blight, disease and impact:
<http://www.fao.org/DOCREP/005/AC450E/ac450e06.htm#b2-4.2%20Taro%20Leaf%20Blight>,
<http://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Pages/TaroLeafBlight>
(with pictures),
<http://www.papuaweb.org/dlib/tema/ubi/paiki-1996-taro-leaf-blight.pdf>
and
<http://www.spc.int/tarogen/Documents/Misc_Publications/TLBimpact2.pdf>
_P. colocasiae_ disease cycle:
<http://www.ediblearoids.org/portals/0/taropest/lucidkey/taropest/media/Html/Fungi/Pcolocasiae/lifecycle.jpg>
_P. colocasiae_ taxonomy:
<http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=232219>
NRCRI:
<http://www.nrcri.gov.ng>
– Mod.DHA

A HealthMap/ProMED-mail map can be accessed at:
<http://healthmap.org/promed/p/1321>.]

[See Also:
2014
—-
Leaf blight, taro – India: (HP)
http://promedmail.org/post/20140904.2747184
2011
—-
Leaf blight, taro – Nigeria: update
http://promedmail.org/post/20110422.1253
2010
—-
Leaf blight, taro – Africa: 1st rep. West Africa
http://promedmail.org/post/20101216.4451
Undiagnosed disease, taro – Cameroon
http://promedmail.org/post/20100715.2365]
………………………………………….sb/dha/je/ml
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