Sorghum Diseases in India

Foliar Diseases of Sorghum
G.N. Odvody 1 and P.R. Hepperly 2
Abstract
The major fungal pathogens of sorghum leaf blades are leaf blight (Exserohilum turcicum), target
leaf spot (Bipolaris sorghicola), gray leaf spot (Cercospora sorghi), ladder spot (C. fusimaculans),
rust (Puccinia purpurea), zonate leaf spot (Gloeocercospora sorghi), sooty stripe
(Ramulispori sorghi) leaf anthracnose (Colletotrichum graminicola), rough leaf spot (Ascochyta
sorghina), and tar spot (Phyllachora sacchari). The leaf sheath diseases are southern
sclerotial rot (Sclerotium rolfsii), banded leaf and sheath blight (Rhizoctonia spp), and zonate
leaf spot on sheaths. Many pathogens survive as mycelia, spores, or sclerotia within sorghum host
residues, on or in soil The sclerotia also exist freely in soil and, depending on the fungus,
germinate to produce initial inoculum of mycelia or conidia. Initial inoculum of the foliar pathogens
is disseminated primarily by wind, rain and soil splash, and soil contact. Many pathogens
survive on living weed hosts or their residues. E. turcicum, C. graminicola, and G. sorghi are
pathogens of hosts other than Sorghum spp. Rhizoctonia spp and S. rolfsii are facultative
parasites of several hosts. Economic impact of foliar pathogens should be assessed before controls
are pursued. Host plant resistance is the primary control of foliar pathogens, but other controls
may be effective and also complement and conserve existing resistance sources. Monogenic and
polygenic resistance to most foliar pathogeris has been identified and may be used individually or in
combination to provide adequate disease control
Introduction
Foliar diseases of sorghum are among the most
common and recognizable diseases of sorghum
[Sorghum bicolor (L.) Moench]. Extensive knowledge
of some diseases and their causal agents is
on record, and only a minimal amount is available
on others.
This discussion deals only with sorghum foliar
diseases caused by fungi. The fungal pathogens,
common names of the diseases they cause,
initial inoculum, and other basic facts are listed
in Table 1. Foliar diseases caused by bacteria, the
foliar phase of sorghum downy mildew, and
nonfoliar phases of anthracnose are discussed in
other papers. The many minor and other re­
ported foliar pathogens of sorghum are enumerated
in Tarr (1962) and the recent compendium
of sorghum diseases (Frederiksen 1986).
Symptomology
Most foliar diseases of sorghum have very distinct
symptoms, especially in mature lesions.
Factors like multiple diseases on the same leaf,
host pigment reactions, and other complex situations
can obscure otherwise typical disease
symptoms. Host pigmentation can dramatically
affect the appearance of disease symptoms and
influence disease assessment. On tan genotypes,
the symptoms of disease are not so obvious and
1. Associate Professor, Plant Pathology, Texas A&M University Research and Extension Center, Route 2, Corpus Christi, TX 78410,
USA.
2. Tropical Research Station, PO Box 70, Mayaguez, Puerto Rico 00709-0070.
Odvody, G.N., and Hepperly, P.R. 1992. Foliar diseases of sorghum. Pages 167-177 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.
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