Soil fumigation with mustard essential oil to control bacterial wilt in tomato

In vitro experiments showed that six isolates, belonging to different biovars, were equally susceptible to mustard essential oil (MEO) vapor. The proportion of cell mortality and colony growth inhibition were directly related to the dose of MEO. A 24 h exposure to 1 or 2 μL of AITC per liter of box volume resulted in mortality of 89% and 92% of cells, respectively, and exposure to 10 μL L −1 resulted in 100% cell mortality. The growth of developing colonies was reduced by 89% at 2 or 4 μL L −1 and by 96% at 6 or 10 μL L −1 . The leakage of intracellular materials increased with increasing doses of MEO vapor. The decline in soil inoculum density by fumigation was directly related to the MEO dose. The initial inoculum density of approximately 3 × 10 5 colony-forming units per gram of soil declined by 67, 91 and 96% at fumigation doses of 25, 50 and 75 μL of allyl isothiocyanate (AITC) per liter of soil, respectively. The pathogen was not detected at a fumigation dose of 100 μL L −1 . Disease control was also related to the fumigation dose. After 48 days, the bacterial wilt symptoms did not develop on the tomatoes when the soil was fumigated at 100 μL L −1 or higher.