Sorghum Diseases in India

Materials and methods
The 1983 experiment was sown on 27 Aug. The
design was a split plot with six replications.
Main plot treatments were four sorghum cultivars
(Dorado, Tortillero, Liberal, and Coludo).
Subplot treatments were fungicide-protected
and nonprotected. Main plots consisted of five
10-m rows, with 0.8 m between rows; subplots
had five 5~m rows. Blocks were separated by
spreader rows. Rows were arranged perpendicular
to prevailing wind direction.
Fungicide was applied with a backpack
sprayer at 15-day intervals, starting from 22 Sep.
Rates were 1 g benomyl plus 4 g mancozeb plus
0.3 mL surfactant L -1 of solution, applied to
runoff.
Disease-severity ratings were carried out at
monthly intervals for the upper and lower
leaves. Area under the disease progress curve
(AUDPC) was calculated from upper and lower
leaves, and for the total plant by calculating a
mean (Wall 1986).
In 1984, the experimental design was
changed to make use of more limited space; this
was a completely randomized design, with two
6
5
4
3
2
1
Treated
Nontreated
Cultivar
Figure 2. Yield levels of two landraces and
two improved sorghum cultivars grown during
the 1983 cropping season in La Lujosa,
Choluteca, the Honduras, and affected by zonate
leaf spot disease.
replications and three treatments, consisting of
no fungicide protection, and with fungicide applications
at 15- and 30-day intervals.
Results
In the trial zonate leaf spot caused a reduction in
yield of nearly 14%. Nonprotected plots averaged
3.37 t ha -1 yield, while those protected from
zonate leaf spot with fungicide averaged 3.92 t
ha -1 (Fig. 2). Disease severity in the latter was
considerably reduced. AUDPC for fungicideprotected
plots had a mean value of 310.34,
while the value for nonprotected plots was
993.03. The improved cultivars Dorado and Tortillero
yielded higher than the landraces Coludo
and Liberal, although the improved cultivars
had higher disease severities (Fig. 3).
In 1984, controlling gray leaf spot resulted in
a significant yield increase of the cv Tortillero.
Without fungicide treatment, this cultivar suffered
a 21% loss of leaf area from gray leaf spot,
and yielded 4.5 t ha- 1 (Table 5). Treated plants
produced 5.6 t ha -1 .
1400
1200
1000
800
600
400
200
Treated
Nontreated
Cultivar
Figure 3. Zonate leaf spot severity levels, as
reflected by the Area under disease progress
curve (AUDPC), on two landraces and two
improved sorghum cultivars treated and nontreated
with fungicidal sprays during the
1983 cropping season in Choluteca, the
Honduras.
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