Evaluation of preplant application of thymol on the suppression of bacterial wilt disease in some tomato genotypes

Abstract

This work reports the evaluation of thymol in the management of bacterial wilt of tomato caused by Ralstonia solanacearum. Sandy-loam top soil was steam-sterilized, stored for six weeks before distribution into experimental pots and tomato transplanting. The experiment was carried out using five tomato genotypes, and was laid out in a completely randomized design in three replications. Twenty mililitre (20 ml) of the bacterial suspension (10⁸ cfu/ml) was introduced into each pot by soil drenching, two hours before thymol application. Thymol at 0.2, 0.4 and 0.6 g/l concentrations were applied into each experimental pot. Pots without thymol served as untreated control. After thymol application, pots were covered with polythene sheet for three days and opened for two days before transplanting. The application of thymol revealed that, there were significant (p ≤ 0.05) delays in number of days to the development of wilt symptom when compared with the untreated control pots. At 5 weeks after transplanting, the highest wilt incidence (86.01%) was recorded in untreated control pots while 10.00% incidence was recorded for Gem pride and Tyre-type tomato genotypes, each at 0.6 g/l application of thymol. At 5 weeks after transplanting, 0.6 g/l concentration significantly reduced bacterial wilt severity with score of 1.00 for all the tomato genotypes used. On disease incidence and severity, there were no interactions between tomato genotypes and thymol concentrations. Thus, the study revealed that thymol application at 0.6 g/l could suppress incidence and severity of bacterial wilt of tomato caused by Ralstonia solanacearum in endemic areas.