May 14, 2020

Southern bacterial wilt now a problem in Louisiana vegetables

Louisiana vegetable growers are beginning to see problems from southern bacterial wilt, one of the most serious diseases of vegetable crops including tomatoes, eggplant and bell peppers.

The disease is caused by the soil-borne bacterium Ralstonia solanacearum, said Raj Singh, LSU AgCenter plant doctor.

“In addition to solanaceous vegetables, the bacterium can cause disease in a wide range of ornamentals,” Singh said. “The pathogen is spread within fields by the movement of infested soil, in surface water and though the handling of infected plants.”

Infected plants rapidly wilt due to loss of water in the of leaves and stems, giving the plants a limp appearance, he said.

“Initially, these plants may recover overnight, but as the disease develops, rapid drying of the foliage occurs leading to permanent wilting and death of the plant,” Singh said. “Brown, sunken cankers are often visible at the base of the plant near the soil line. Symptomatic plants exhibit discoloration of the vascular system and the pith.”

Managing southern bacterial wilt in soils previously infected with the bacterium presents a real challenge, Singh said.

“There are no effective chemicals registered for commercial as well as home growers,” he said. “Disease prevention is the key in reducing the spread to new, uninfected sites.”

Soil solarization of contaminated fields during summer may also help reduce the initial population of bacterium in the soil.

Cultural management of southern bacterial wilt includes avoiding planting susceptible crops in infested fields, planting on raised beds, avoiding late plantings of tomatoes in areas known to be infested and using long-term rotations with non-host crops such as corn, beans and cabbage.

Commercial as well as home growers must follow good sanitation practices to reduce the spread of the disease including avoiding movement of infested soils, avoiding movement of stakes from known infested sites to new sites and proper cleaning of tools.

“There are no commercially available resistant or tolerant varieties that we can recommend,” Singh said.

– Johnny Morgan, Luisiana State University

Photo at top: Tomato plant infected with southern bacterial wilt. Photo: Raj Singh/LSU AgCenter