Sorghum Diseases in India

fall on the ground remain viable for 7 months
(Futrell and Webster 1966). Singh (1964) and Futrell
and Webster (1966) hypothesize that ascospores
and conidia may infect collateral hosts
that flower prior to sorghum, and conidia in the
honeydew of collateral hosts provide fresh inoculum
to initiate primary infection in sorghum.
This has not been documented.
Within 5-12 days after infection in sorghum,
the pathogen produces millions of conidia, in
honeydew, to infect spikelets that flower subsequently
in the same panicle or in different panicles.
The pathogen spreads rapidly, probably
carried by flies, bees, and other insects (Futrell
and Webster 1966) and rain splashes. However,
insects may facilitate pollination, and that in
turn reduces infection.
In wet conditions Cerebella overgrows honeydew
and sclerotial production is arrested
(Futrell and Webster 1966), but in dry weather
well-differentiated sclerotia are produced and
the honeydew forms a hard white crust. In the
next season, ascospores are produced from sclerotia
(Singh 1964); conidia are produced from
dried honeydew (Futrell and Webster 1966) or
germinating sclerotia (C.S. Sangitarao and B.N.
Ghoderao, Punjabrao Krishi Vidyapeeth, Akola,
India, personal communication 1981). The sexual
and asexual spores may infect collateral hosts or
they may infect sorghum to complete the disease
cycle, but what actually occurs is still unknown.
Demonstration, in the absence of sorghum, of
inoculum production in collateral hosts through
several seasons would help clear up this matter.
The role of wild sorghums in the disease cycle
needs investigation.
Host range
Several workers have examined the host range
of Spacelia sorghi; their reports are listed in
Table 1. Except for that of Ramakrishnan (1947),
others are based on artificial inoculation, but in
none of the experiments was an adequate noninoculated
control maintained. Cross inoculation
tests to prove pathogenicity of isolates were
performed only by Reddy et al. (1969) on Pennisetum
typhoides, by Sundaram et al. (1970) on
P. orientale x P. typhoides, and by Sundaram and
Singh (1975) on Ischaemum pilosum. Some workers
reported Cenchrus ciliaris, Panicum maximum,
and P. typhoides as hosts of S. sorghi, whereas
other workers failed to confirm these. Futrell
and Webster (1966) reported maize to be a collateral
host and subsequently Chinnadurai and
Govindaswamy (1971a) found maize ovaries replaced
by fungal stromata containing conidia
that did not ooze out. Futrell and Webster (1966)
also reported that pearl millet ovaries are killed
by S. sorghi and do not support the fungal
stromata. Clearly, more studies are required—
not only to determine the collateral hosts but
also to elucidate their roles in the disease cycle.
Control
Several strategies for the control of sorghum ergot
have been advocated. Quarantine has been
effective in excluding the pathogen from countries
where ergot is not found. Australia and
USA, for example, are countries with strict quarantine
regulations against the entry of the pathogen
on seeds.
Several researchers in India have shown, under
experimental conditions, the utility of early
sowing to avoid ergot (Singh 1964, Sangitrao et
al. 1979; Anahosur and Patil 1982). Early sowing
was invariably required to avoid the disease.
Singh (1964) thought that an advantage similar
to that of early sowing might be achieved by
using early-maturing varieties and hybrids, but
early-maturing cultivars sown early are likely to
suffer from grain molds.
Sundaram (1968) suggested sowing pathogen-free
seed by steeping seeds in 5% salt solution
to remove sclerotia (C.S. Sangitrao and B.N.
Ghoderao, Punjabrao Krishi Vidyapeeth, Akola,
India, personal communication 1981). Removal
of collateral hosts in and around fields and
rouging of infected plants are other cultural
methods of control (Sundaram 1968). Ensuring
availability of pollen during flowering reduces
pearl millet ergot (Thakur et al. 1983), but evidence
of its practicability for large-scale use in
sorghum is lacking.
Fungicides were reported to control ergot
(Gangadharan et al. 1976; Anahosur 1979), but is
considered impractical, ineffective, and noneconomical
except in small plots of valuable
breeding lines.
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