Evaluation of Cultural Practices, Fungicides and Bio Control Agents for the Control of Tomato Late Blight (Phytophthora infestans (Mont) de Bary) in West Showa, Ethiopia

Abstract

Late blight caused by Phytophthora infestans (Mont) de Bary) is one of the most important and widespread pathogenic soil borne fungal pathogen, which posed a significant constraint to tomato (Lycopersicon esculentum Mill.) production mainly in the rainy season. Therefore, this study was carried out to evaluate cultural practices, fungicides and bio agents with an attempt to identify the best option(s) for controlling tomato late blight under field condition. The study was conducted during the main cropping season of 2012 at Guder, Toke kutaye district of West Showa, Ethiopia. Treatments consisted of two fungicides (Victory 72 WP and Ridomil gold), mixture of micro nutrients (copper sulphate, zinc sulphate and Ferrous sulphate in combination), two mulch types (plastic and dry grass mulch) and antagonistic bio agents (Pseudomonas fluorescens, Trichoderma viride and Pseudomonas fluorescens+ Trichoderma viride) along with untreated control. The treatments were laid out in randomized complete block design (RCBD) with three replications. Results indicated that there was significant differences among treatments in terms of disease severity (DS), area under disease progressive curve (AUDPC), disease progressive rate (r), yield and yield components, and cost-benefit ratio. The application of fungicide treatments considerably reduced late blight progress, with a corresponding increase in tomato fruit yields over the other treatments including control. Victory 72 WP and Ridomil gold treated plots respectively recorded significantly lower DS (15.57 % and 18.9%), AUDPC (711.7%_days and 894.6_days), disease progressive rate (0.65 and 0.68), and higher marketable fruit yield (210.98 kg / ha and 184.9 kg/ha). Moreover, plot sprayed with combination of micronutrient (ZnSO4.H2O + CuSO4.5H2O + FeSO4.7H2O) showed lower disease severity (36.67%) next to Victory 72 WP and Ridomil gold. The biocontrol agents and both mulch types did not significantly differed from each other as well as from the control in disease severity. Apart from Victory 72 WP and Ridomil gold, the application of micronutients, seed treatment with P. fluorescens alone and the use of plastic mulch showed significantly lower AUDPC value over the other treatments. Significantly lower per cent fruit infection was recorded from plots treated with Victory 72 WP and Ridomil gold and with the use of plastic mulch. The application of Victory 72 WP, Ridomil gold, mixture of micronutrients, and the use of plastic mulch gave significantly higher marketable yield over the other treatments including control. The result of the cost- benefit analysis indicated that plastic and grass mulch recorded the highest total variable costs. Likewise, the lowest variable cost was observed with the application of micronutrients and bio control agents. Nevertheless, the highest gross field benefit was maintained from Victory 72 WP followed by Ridomil gold. In addition, the highest net benefit was obtained from Victory 72 WP and Ridomil gold with mean values of 161,464 and 139,784 Birr/ha, respectively. The highest marginal rate of return (15,902 %) was obtained from micronutrient treatments when compared with untreated control. followed by Victory 72 WP (13,106 %). The application of both Victory 72 WP and Ridomil gold fungicides significantly reduced disease development and increased marketable tomato fruit yield over all the other treatments including control.