Evaluation of Selected Botanical Spray on Field Management of Taro leaf blight and yield attributes of Taro (Colocasia esculenta L.) cultivars in Enugu State, Southeastern Nigeria

Abstract

The dwindling availability of synthetic fungicides together with increasing public concern on the environmental safety means that the use of plant materials to manage field pathogens are attracting increased attention. Therefore, the aim of this study was to determine the effect of botanicals on leaves growth, field management of Phytophthora colocasiae disease incidence, disease severity and yield   attributes of taro cultivars. The study was carried out at Enugu State Polytechnic Iwollo Teaching and Research Farm.  The experiment was laid out as a 3x 5 factorial in randomized complete block design (RCBD) with three replications. The experimental treatment materials consisted of three taro cultivars – Nachi, Odogolo and Ugwuta  as main plot, while the sub- plots consisted of  three botanicals- Neem (Azadiratchta indica), siam weed (Chomolanenae  odorata) and Eucalypus spp; a synthetic fungicide (Ridomil gold plus) as a standard positive treatment  and  control ( (No treatment) as a standard negative treatment. Data collected were analyzed by analysis of variance (ANOVA), while Fisher’s least significant (F-LSD) was used to separate means where significant at 5% probability level.   It was evident that variability existed across the taro cultivars and botanicals on   number of leaves/stand, disease incidence, disease severity (%) and yield indices (kg/stand), (number of cormels/stand,cormel weight/stand, corm weight/ stand, corm circumference/stand, total tuber weight/stand (kg/stand). Odogolo cultivar significantly (P < 0.05) had the highest number of leaves values (21.10, 21.50 and 14.90), while Ugwuta cultivar had the least number of leaves values (11.90, 19.80 and 14.70) at 90 to 150 days after planting, respectively. Ridomil gold significantly (P < 0.05) recorded the highest number of leaves (21.90, 28.70 and 21.60), and the least number of leaves (10.90, 15.20 and 9.60) was recorded by the control treatment at 90 to 150 days after planting.  Disease incidence (%) significantly (P <.0.05) varied among the botanicals except at 120 and 150 days after planting with Ridomil gold scored the least disease incidence (%) (25.70, 9.10 and 3.30) and then the highest (100.00, 100.0 and 100.00) was scored by the control treatment throughout the sampling periods at 90 – 150 days after planting. Among the cultivars, Nachi cultivar scored the least disease incidence (%) (57.30, 62.40 and 41.90), and the highest disease incidence (%) (85.90, 66.20 and 43.20) was scored by the Ugwuta cultivar at 90 - 150 days after planting, respectively.  Disease severity (%) also had significant (P < 0.05) variations among the botanicals throughout the study periods with Ridomil gold scoring the least (4.10, 0.70 and 0.30) disease severity, while the control treatment scored the highest disease severity (%) values (52.90, 63.80 and 49.90 throughout the study periods. Among the cultivars, Ugwuta cultivar consistently scored the highest significant (P < 0.05) disease severity (%) (29.30, 33.80 and 22.70, and the least disease severity score (19.50, 20.30 and 14.10) was consistently scored by the Nachi cultivar throughout the study periods. Cultivars and botanicals significantly (P< 0.05) differed in all yield indices (number of cormels/stand, cormel weight/stand, corm weight/stand, corm circumference/stand, total tuber weight/stand (kg/stand and tons/hectare). Odogolo cultivar significantly had the highest total tuber yield per hectare (t/ha) (27.20), while Nachi cultivar recorded the least total tuber (t/ha) (12.20) at harvest. The study revealed that botanicals affected the agronomic and the field management of taro leaf blight disease of taro cultivars.