Sorghum Diseases in India

In recent years, the government has attempted
to increase sorghum production through
the creation of a sorghum research program directed
toward the development of improved cultivars
and cultivation practices.
In a socioeconomic study of sorghum production
in the southern parts of the Honduras,
De Walt (1982) found that the constraints to sorghum
production were many, but among these
was no mention of diseases. This reflects an ignorance
on the part of the subsistence farmer, as
he blames only visible pests (mainly insects) for
damage seen on his plants. If these farmers are
asked to name the major constraints on their sorghum
crop, they will talk about insect pests,
which to them include what we know as diseases.
The vast majority of subsistence farmers cultivate
marginal lands. Quite often, they sow on
hilly slopes. Soil fertility is generally low. Little
attention is given to sorghum fields through the
growing season. Consequently, and in addition
to the limitations dictated by the restricted gene
pool within traditional landraces, yields are low
and well below the world average (FAO 1985;
Navarro 1979; SRRNN 1984).
Sorghum is sown according to several different
cropping schemes, although the majority of
farmers sow sorghum in association with maize.
This is done in different ways and several spatial
arrangements can be found. There are several
pathogens, such as Peronosclerospora sorghi, the
causal agent of sorghum downy mildew that
have the ability to cause disease both in maize
and in sorghum. Sorghum is also sown without
intercropping with maize (De Walt and De Walt
1984; SRRNN 1984).
If sorghum production is to increase in the
Honduras, it is essential to document the importance
of sorghum diseases. The role of these diseases
in relation to low yields must be determined.
Means by which these losses can be reduced
is a major priority. Whether landrace cultivars
are going to be improved or replaced by
new higher-yielding introductions (Guiragossian
1983) is of paramount concern, because
little is gained by the use of otherwise welladapted
high-yielding sorghums if disease-management
strategies are unavailable or not
practiced.
Since the vast majority of sorghum growers
sow on marginal land and experiment stations
operated by the Ministry of Agriculture are lo­
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cated in fertility valleys where fields are flat, information
generated by such experiment stations
often does not reflect the realities of
growing sorghum on hillsides and other poor
soils (Chambers and Ghildyial 1985). For this
reason, the experiments reported here were conducted,
when possible, in farmers' fields.
The areas where sorghum is grown, as described
by Nolasco (1983), are in Choluteca,
Vella, El Paraiso, Limpira, Francisco Morazan,
and Olancho. Most of it is grown in Choluteca
and Valle (Fig. 1).
Throughout the 3-year period 1983-85,21 sorghum
diseases were identified (Table 1). Diseases
found in all areas were acremonium wilt,
anthracnose, gray leaf spot, grain molds, ladder
spot, leaf blight, loose smut, maize dwarf mosaic,
rust, sugarcane mosaic, and zonate leaf
spot. Some diseases did not occur in all areas.
Downy mildew was not observed in Valle and
Choluteca. Maize chlorotic dwarf was seen only
in one location in El Paraiso. Oval leaf spot was
not found in Valle or Francisco Morazan. Other
diseases, namely bacterial stripe, charcoal rot,
covered smut, head blight, and sheath blight,
occurred with less frequency and were observed
in Choluteca, where the majority of the work
was carried out. Head blight was also observed
in El Paraiso. Charcoal rot was only seen on improved
cultivars.
In the Comayagua area, downy mildew, ladder
spot, gray leaf spot, and rust were highest in
severity and prevalence in 1985.
In Francisco Morazan, rust, gray leaf spot,
and ladder spot diseases were highest in disease
index values (severity x prevalence). In El Paraiso,
gray leaf spot and rust disease were highest.
For Valle and Choluteca, the diseases with highest
index values in 1985 were gray leaf spot and
oval leaf spot.
Maize Dwarf Mosaic and
Acremonium Wilt
Acremonium wilt (AW) is caused by the fungus
Acremonium strictum W. Gams. It was only recently
reported and described in the Americas
(Frederiksen 1986), This vascular disease was
found wherever sorghum was observed for diseases.
The same is true for maize dwarf mosaic
(MDM), a systemic disease caused by the maize
dwarf mosaic virus (MDMV). The host range for