Sorghum Diseases in India

Sorghum Diseases in Western Africa
M.D. Thomas 1
Abstract
In western Africa sorghum (Sorghum bicolor) is attacked by several fungi, bacteria, viruses, and
by the parasitic weed Striga hermonthica. Sorghum is grown mainly in the Sudanian Zone (500-
1000 mm rainfall) and in the northern Guinean Zone (1000-1200 mm rainfall). Some sorghum is
also grown in the Sahelian Zone (400-500 mm rainfall). The importance of any of the sorghum
diseases depends to a large extent on the zone in which the crop is grown. In local and introduced
genotypes alike, diseases such as gray leaf spot and leaf anthracnose are more prevalent in the
northern Guinean and Sudanian zones; sooty stripe and long smut occur more frequently in the
Sudanian Zone. Grain mold is found mostly in introduced genotypes which mature during periods
of relatively high rainfall. Oval leaf spot, zonate leaf spot, leaf blight, head smut, and covered smut
occur at low levels in both the northern Guinean and Sudanian Zones. Head smut is a particular
problem in farmers' fields. Striga hermonthica occurs abundantly in all zones and attacks all
genotypes. Preliminary data indicate that symptoms of gray leaf spot first appear between flowering
and 10 days after in Burkina Faso. The progress of the disease is slow and exceeds 75% leaf area
infected only at maturity. In contrast, symptoms of leaf anthracnose appear early, the disease
progresses rapidly, and kills top leaves during grain formation. Soil shading with groundnut
suppressed Striga in farmers' fields.
Introduction
Sorghum [Sorghum bicolor (L) Moench] is grown
widely in many countries in semi-arid western
Africa. In several of these countries, sorghum
can be regarded either as the staple food or the
second most important source of energy for the
population. Most of the sorghum is grown in the
Sudanian Zone (500-1000 mm rainfall) and the
northern Guinean Zone (1000-1200 mm rainfall).
Some sorghum is also grown in the southern
Sahelian Zone (400-500 mm rainfall).
In western Africa sorghum is attacked by
several fungi, bacteria, viruses, and the parasitic
weed Striga hermonthica (Del.) Benth (Table 1).
The situation with nematodes is not quite clear
and there appears to be no report of nematode
infection of sorghum in western Africa. There is
variation in incidence and severity of the dis­
1. Principal Sorghum Pathologist, ICRISAT. B.P, 910, Bobo-Dioulasso, Burkina Faso.
eases according to the agroecological zones
mentioned above. Thus, the importance of any
one of the sorghum diseases in western Africa
depends to a large extent on the zone where
the crop is growing. Importance is also related
to whether a disease occurs on local landraces
or on introduced genotypes. There appears to
be "pockets" within western Africa for the
occurrence of some diseases. For example,
symptoms of downy mildew and virus-like
symptoms have been reported in some countries
(Tyagi 1980, Zummo 1984), whereas in
many countries these two categories of symptoms
are absent, or at least have not been reported.
In general the importance of a disease
is related to several other factors, such as the
progress of the disease during the different
growth stages of the host and the effect of the
disease on grain yield.
Thomas, M.D. 1992. Sorghum diseases in western Africa. Pages 25-29 in Sorghum and millets diseases: a second world review,
(de Milliano, W.A.J., Frederiksen, R.A., and Bengston, G.D., eds). Patancheru, A.P. 502 324, India; International Crops Research
Institute for the Semi-Arid Tropics. (CP 733).
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