Control of tomato bacterial wilt in a hydroponic system with iodine

Iodine (Isub(2)) as a disinfectant of the nutrient solution for a hydroponic system was evaluated. In a test tube experiment, Isub(2) at 1 microg/ml sterilized distilled water for 5 min inactivated Ralstonia solanacearum (Rs). Treatment of nutrient solution with 3 microg/ml of Isub(2) for 15 min before transplanting tomato seedlings into a hydroponic system sufficiently controlled the bacterial wilt disease. In contrast, 83.3% of the plants in the control system were diseased at 30 days after inoculation. In a nutrient solution in which tomatoes were already growing, Rs was not detected immediately after Isub(2) treatment but was detectable 3 days after the treatment, and eventually the bacterial population reached the same level of the control. The disease incidence in systems treated with 3 and 5 microg Isub(2)/ml nutrient solution was lower than that in untreated control. These results suggest that Isub(2) is a highly effective disinfectant against Rs and can control tomato bacterial wilt in a hydroponic system.