STUDIES OH THE CONTROL OF LEAF SPOT DISEASES OF SESAME(Sesamum i n d i c um L. ) IN NIGERIA

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STUDIES OH THE CONTROL OF LEAF SPOT DISEASES OF SESAME(Sesamum i n d i c um L. ) IN NIGERIA

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.. 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 sesamevi 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.

STUDIES OH THE CONTROL OF LEAF SPOT DISEASES OF SESAME(Sesamum i n d i c um L. ) IN NIGERIA

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