Evaluation of Essential Oils Against Potato Late Blight (Phytophthora infestans (Mont.) de Bary) at Holleta, Ethiopia

This study was conducted to evaluate essential oils from Croton macrostachyus Hochst. ex Delile, Eucalyptus globulus Labill., Allium sativum L., Cymbopogon citratus (DC.) Stapf, Cymbopogon martini (Roxb.) W.Watson, Rosmarinus officinalis L. and Thymus schimperi Ronniger using four concentrations (l mL, 2 mL, 3 mL, 4 mL) and three sprays against potato (Solanum tuberosum L.) late blight disease. Two improved potato varieties were planted using randomized complete block design with factorial combinations in three replications. Analysis of disease incidence means at 53 and 60 days after planting showed highly significant differences between varieties and among sources of essential oils. Furthermore, the combined effect of essential oils and potato varieties on disease severity showed significant differences. Disease severity was maintained from 25% to 48% (Jalene); 13% to 30% (Gudene) with essential oils while it was maintained between 92% and 95% (Jalene); 37% to 38% (Gudene) for control plants. The lowest disease percentage of disease severity was obtained on plants treated with A. sativum for Jalene variety while on plants sprayed with C. macrostachyus, E. globulus and T. schimperi for Gudene variety. The lowest disease progress rate 0.198/day and 0.162/day as well as values of area under disease progress curve 228% days and 93% days were obtained for varieties Jalene and Gudene, respectively. Maximum reduction in mean disease severity was exhibited by garlic for varieties Jalene (28.3%) and Gudene (16.3%), as compared to the control (93.3% for Jalene and 37.5% for Gudene). Therefore, results indicated the potentials of essential oils to minimize effects of potato late blight disease. Communities involved in potato production could use the current results as base line information to find alternative management options for late blight disease which has no effect on human health and environment. However, further investigation is required on essential oils affordability and availability to farmers across different locations.