Controlling Bacterial Wilt

Bacterial wilt can wipe out a tomato crop if a susceptible variety is planted in infected soil at a time when the bacteria are active.

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The disease spreads rapidly down the rows. If it attacks a young plant, it can cause considerable damage; a plant that appears healthy one day may be withered the day after.

Initially, it may seem that a dripper on the irrigation line has become blocked or a cutworm has damaged the stem of the plant. So, to test whether the wilting has indeed been caused by bacterial wilt, cut a stem about 20cm from the wilted tip and suspend it in a glass of water. If the plant has been affected, a stream of milky bacteria will flow from the cut stem after a few hours.

Bacterial wilt in tomatoes is caused by Pseudomonas solanacearum, and the strain encountered in South Africa is Biovar 1, Race 2. The bacteria are inactive at temperatures below 18°C and highly destructive in hot, wet conditions.