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ABSTRACT

Laboratory, glasshouse and field investigations were
conducted to assess the effects of dry heat seed
treatment, foliar-applied fungicides and inter- and
intra-row spacings on leaf spot diseases of sesame
induced by Xanthomonas campesstris pv. sesasmi and
Cercospora sesami during the 1990 and 1991 wet seasons
at Samaru. Four dry heat treatments were used to treat,
the seeds and their effects assessed in laboratory,
glasshouse and. field experiments. These were 100°C for
15min, 90°C for 24 h, 80°C for 72 h and 70°C for 96 h.
The control received no heat treatment. For fungicidal
control of leaf spot diseases, two fungicides,
carbendazim + maneb and manco2eb were each used at two
concentrations, 2.22 and 3.70 g a.i./l, and 5.04 and
7.04 g a.i./l respectiveiy, in the fieId- trials. The
effect of plant spacing on leaf spot diseases of sesame
was investigated in field trials by establishing three
inter-row (50, 75 and 100 cm) and three intra-row (15,
20 and 25 cm) spacings.
In the laboratory studies, dry heat treatment at 90°C
for 24 h resulted, in the lowest incidence of both fungi
and bacteria. Pseudomonas sp., Xanthamanas campestris
pv. sesami and Macr-ophomina. phaseolina were detected
in seeds subjected to any of the treatments..
v.
However, the occurrence of Alternaria spp. ,
Helminthosporim Spp.A s p e r g i l l u s niger and Curvularia
sp. were not consistent with the treatments. Seed
germination was adversely affected by heat treatment at
90°C for 24 h. however, germination was over 60% in all.
cases.
Assessment of the effect of dry heat seed treatment in
the glasshouse also indicated that 90°C for 24 h
adversely affected sesame seedling emergence. Shoot
length, stem diameter, root length as well as seedling
blight severity of sesame seedlings were however not
significantly affected by dry heat seed treatment –
The two-year field trials showed that dry heat seed
treatment at 90°C, 80°C and 70°C for 24, 72 and 98 h,
respectively,, significantly reduced both types of leaf
spot disease incidence and severity, number of diseased
leaves and number of leaves shed per plant in cultiver
69A-205. Significant effects of heat treatment on the
magnitudes of these parameters for cultivars S5B-58 and
E8 were found only during the 1991 field trial. Dry
heat seed treatment did not significantly affect yield
and yield components of sesame Field evaluation of foliar-applied fungicides showed
that carbendazim + maneb and mancozeb significantly
reduced the Cercospora leaf spot disease incidence and
severity, number of diseased leaves and number of
leaves shed per plant without significant effect on
yield and yield components of sesame in both years.
There were no significant differences among the. effects
of the chemicals and their concentrations.
Investigation of the effect of inter—and intra-row
spacings conducted during 1990 and 1991 field trials
showed. significantly high disease incidence and
severity, numbers of diseased leaves and leaves shed
per -plant within closely spaced plants. Increase in
intra-row spacings from 1.5 to 25 cm significantly
increased, numbers of branches and capsules and seed
weight per plant. While increase in inter-row spacings
from 50 to 75 cm. increased seed weight per plot, furtherincrease
in spacing reduced yield per plot due to
decreased plant population. Both inter- and intra-row
spacings did not significantly affect plant height and.
height to the lowest capsules in both years. Effects of
interactions between inter- and intra-row spacings on
number of capsules per plant and disease severity were
found to be significant.Field evaluation of foliar-applied fungicides showed
that carbendazim + maneb and mancozeb significantly
reduced the Cercospora leaf spot disease incidence and
severity, number of diseased leaves and number of
leaves shed per plant without significant effect on
yield and yield components of sesame in both years.
There were no significant differences among the. effects
of the chemicals and their concentrations.
Investigation of the effect of inter—and intra-row
spacings conducted during 1990 and 1991 field trials
showed. significantly high disease incidence and
severity, numbers of diseased leaves and leaves shed
per -plant within closely spaced plants. Increase in
intra-row spacings from 1.5 to 25 cm significantly
increased, numbers of branches and capsules and seed
weight per plant. While increase in inter-row spacings
from 50 to 75 cm. increased seed weight per plot, furtherincrease
in spacing reduced yield per plot due to
decreased plant population. Both inter- and intra-row
spacings did not significantly affect plant height and.
height to the lowest capsules in both years. Effects of
interactions between inter- and intra-row spacings on
number of capsules per plant and disease severity were
found to be significant.Field evaluation of foliar-applied fungicides showed
that carbendazim + maneb and mancozeb significantly
reduced the Cercospora leaf spot disease incidence and
severity, number of diseased leaves and number of
leaves shed per plant without significant effect on
yield and yield components of sesame in both years.
There were no significant differences among the. effects
of the chemicals and their concentrations.
Investigation of the effect of inter—and intra-row
spacings conducted during 1990 and 1991 field trials
showed. significantly high disease incidence and
severity, numbers of diseased leaves and leaves shed
per -plant within closely spaced plants. Increase in
intra-row spacings from 1.5 to 25 cm significantly
increased, numbers of branches and capsules and seed
weight per plant. While increase in inter-row spacings
from 50 to 75 cm. increased seed weight per plot, furtherincrease
in spacing reduced yield per plot due to
decreased plant population. Both inter- and intra-row
spacings did not significantly affect plant height and.
height to the lowest capsules in both years. Effects of
interactions between inter- and intra-row spacings on
number of capsules per plant and disease severity were
found to be significant.

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