Sorghum Diseases in India

Zonate leaf spot, a disease incited by Gloeocercospora
sorghi, may, on a regional basis, be the
third most prevalent of the foliar diseases. It is a
serious problem in Dominican Republic and
Panama (Escobedo et al. 1979; Perez Duverge et
al 1984; Jimenez 1984; Wall 1980; Meckenstock
and Wall 1987). A higher incidence of zonate leaf
spot was recorded in fields where sorghum was
sown alone than in sorghum intercropped with
maize (Wall 1986). This foliar disease is most
commonly found on the older leaves and
sheaths, but it can reach epidemic proportions
under favorable conditions and attack all foliage.
A 14% loss in yield was measured under
high disease severity levels (Meckenstock and
Wall 1987).
Ramulispora sorghicola, causal agent of oval
leaf spot, first reported on herbarium samples
from Haiti in 1960 (Harris 1960) had not been
recorded on the American mainland. Now it can
be found in certain areas of El Salvador and the
Honduras, reaching higher severity levels than
other foliar diseases and causing defoliation
(Wall 1986).
Anthracnose (Colletotrichum graminicola) can
affect all aerial parts of the sorghum plant
(Frederiksen 1986). In Guatemala, where it is
considered an important disease (Escobedo et al.
1979), the pathogen can be found sporulating on
infected individual grains of susceptible sorghum
panicles (Frederiksen 1986). The foliar
stage of the disease can be found on young
plants early in the growing season. In the authors'
experience, anthracnose usually becomes
less important as the crop matures and the rains
subside and other foliar diseases, such as gray
leaf spot and rust, become more prevalent. Anthracnose
is favored by hot and humid conditions.
In Panama, for instance, it is one of the
most important problems in sorghum production
(Jimenez 1984). Johnsongrass is a wild host
of this disease, as well.
Incidence of leaf blight (Exserohilum turcicum)
usually is low but every now and then it can
flare up to noticeable levels. Again, johnsongrass
is one of its hosts. This disease has been
serious in certain parts of Mexico in recent years.
Many imported sorghum-sudan hybrids, grown
for forage, are particularly susceptible to leaf
blight in Central America.
Another species of Cercospora (C. fusimacutaws),
causing ladder leaf spot, has been described
recently on sorghum (Wall et al. 1987). It
is not as widespread as gray leaf spot, but occurrence
has been reported from the United States
of America to Brazil. Resistance to this disease,
apparently independent of that to G sorghi, has
been observed. Symptoms differ from those of
gray leaf spot mainly in the scalariform pattern
of the lesions Bacterial leaf stripe (Pseudomonas
andropogonis), also found in many sorghum-producing
areas, is of minor importance. In breeding
nurseries, certain cultivars show a marked
susceptibility to this disease.
Sheath blight, caused by Scterotium rolfsii, has
been observed in the Honduras and El Salvador,
but is of minor importance.
Systemic diseases
Maize dwarf mosaic virus (MDMV) and sugarcane
mosaic are aphid-transmitted virus diseases
found throughout Central America. They
are also spread by mechanic transmission. They
can hardly be distinguished by symptoms alone;
in fact, the two can occur together. The first
is common on johnsongrass and other wild
grasses; the second one can be found on
sorghum where sugarcane is also grown. In a
comparison of healthy vs diseased sorghum,
MDMV-infected plants had 52% less yield than
healthy plants (Meckenstock and Wall 1987).
These virus diseases also occur on maize.
Maize chlorotic dwarf, another virus disease,
has been reported in a remote area of the Honduras.
Unlike those previously mentioned, this
virus is transmitted by leaf-hoppers (Graminella
sp), and is not known to be mechanically transmitted.
At this time, this disease is of no significant
importance.
Sorghum downy mildew (SDM), caused by
Peronosclerospora sorghi, is an important disease
of maize and of sorghum. It is found in southeastern
Guatemala, and in several sorghum-producing
areas of El Salvador, the Honduras, and
Dominican Republic (Castellanos et al. 1982;
Wall 1980; Fernandez and Meckenstock 1987;
Perez Duverge et al. 1984). Fortunately, this disease
is absent in some important sorghum production
areas, such as the southern departments
of the Honduras.
Oospores of P. sorghi are carried with sorghum
seed; they can also be found in the glumes
that remain attached to the few seeds occasionally
formed on systemically infected plants
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