Sorghum Diseases in India

Epidemiology of Sorghum Diseases in Central America:
a Case Study
G.C. Wall 1 , R.A. Frederiksen 2 , J. Craig 3 , and M.J. Jeger 4
Abstract
Field surveys were carried out in 1983, 1984, and 1985 in the Honduras, Central America.
Twenty-one sorghum diseases were identified. Eight of these were studied with regard to their effect
on yield. Near-isogenic populations that were resistant, intermediate, or susceptible to sorghum
downy mildew (SDM) were sown in a disease-free area and in a SDM endemic area; a 43% disease
incidence reduced yield by 44%.
Paired comparisons of diseased and healthy plants showed that maize dwarf mosaic (MDM)
caused a 52% yield reduction on 'maicillos,' the traditional landraces. Acremonium wilt caused a
36% yield reduction on a susceptible cv (BTx 623) and a 33% loss on maicillos. A holistic,
multivariate study, using data from subsistence farmers' fields, produced a multiple regression
model for estimating yields on the basis of plant height, panicle length, and disease severity. The
yield reduction estimate for gray leaf spot was 16%; for oval leaf spot, 6%; and for rust, 4%.
In fungicide-protected and nonprotected experiments, zonate leaf spot was estimated to cause
15% yield loss, and gray leaf spot 14%.
Comparing cropping systems, sorghum-maize intercropping was found to have lower oval leaf
spot severity than sorghum growing alone, but MDM incidence was higher. Early sowing of
maicillos resulted in higher disease severities than did late sowing. August sowings of improved
cultivars had fewer diseases, but higher severities than did August-sown maicillos. Sorghum-bean
intercropping did not affect sorghum disease severities. Various sources of disease resistance were
identified by screening international and local nurseries.
Introduction
The area of highest sorghum production in Central
America lies along its Pacific coast in parts of
Guatemala, the Honduras, Nicaragua, and El
Salvador. Epidemiological studies on sorghum
diseases carried out in the Honduras from 1983
to 1985 are reported here.
As is typical of this area in Central America,
sorghum production in the Honduras is mainly
traditional landraces sown by subsistence
farmers; 93% of all production in the Honduras
is in the hands of these resource-poor farmers
(SRRNN 1984). The crop is used for feeding
poultry, swine, cattle, and horses, and as human
food. One third of the total production is used
for human consumption (De Walt 1982).
Sorghum is grown as a risk-reducing crop. In
the semi-arid areas where growing maize is
risky, sorghum offers a more reliable food
source. Even though annual rainfall is ca. 1600
mm, the rainy season normally has an interrupted
period called 'canicula'. This canicula often
limits maize yields, but not so with sorghum.
1. Assistant Professor, College of Agriculture and Life Sciences, University of Guam, Mangilao, GU 96923, USA.
2. Professor, Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA.
3. Research Plant Pathologist, ARS/USDA, PO Drawer DN, College Station, TX 77841, USA.
4. Head, Overseas Pest Research, Tropical Development and Research Institute, 56-62 Gray's Inn Road, London WC 1X 8LU, UK.
Wall, G.C., Frederiksen, R.A., Craig, J., and Jege, M.J. 1992. Epidemiology of sorghum diseases in Central America: a case study.
Pages 303-317in 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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