Control of bacterial soft rot disease of Chinese cabbage by geraniol, thymol, and o-vanillin and the residue characteristics in cabbage

Abstract

The development of antibiotic alternatives is an important issue for controlling plant-pathogenic bacterial disease due to the development of resistance and limited use guidelines for antibacterial pesticides in crop fields. Geraniol, thymol, and ovanillin were known to have antibacterial activity; however, the antibacterial activity and the disease control efficacy against Erwinia carotovora were not reported in the crop. In this research, the minimal inhibitory concentration (MIC) and the disease control efficacy of geraniol, thymol, and o-vanillin were investigated as well as the residues in cabbage. MICs of geraniol, thymol, and o-vanillin were 125-250 µg mL 1 , and MIC of a mixture of the three compounds was 93.8 µg mL 1 against E. carotovora. The fractional inhibitory concentration index of the mixture agent was 0.625, and it presented an additive effect. The disease protection efficacy of the mixture agent was 72.7% for bacterial soft rot after twice application on 340 mg L 1 . The initial residues of geraniol, thymol, and o-vanillin were 0.66, 3.72, and 0.28 mg kg 1 , respectively; however, 50% of dissipation times for all three compounds were below a day.