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Bacterial Wilt

Plant disease · Ralstonia solanacearum species complex

Description​

Bacterial wilt is a soilborne disease that blocks water movement through a plant’s vascular tissue. The name commonly refers to disease caused by bacteria in the Ralstonia solanacearum species complex, which affects tomatoes, potatoes, peppers, eggplants, and many other hosts. In warm conditions, an affected plant may wilt rapidly even when the soil is moist. Leaves may initially recover overnight, then wilt permanently as the infection spreads. Growth can slow, leaves may yellow, and the whole plant can eventually die. The bacteria can persist in soil, infected plant material, and some weeds, and can spread in contaminated water, soil, tools, and transplants. They enter through roots, particularly where roots are damaged. “Bacterial wilt” can also describe a different disease of cucumbers and other cucurbits, caused by Erwinia tracheiphila and spread by cucumber beetles. Identifying the host matters because prevention differs.

Symptoms​

  • Wilting
  • Yellowing leaves
  • Stunted growth
  • Leaves dropping

How to Identify​

Suspect Ralstonia bacterial wilt when a plant wilts despite moist soil, especially during warm weather, and does not recover after watering. Cut a lower stem: brown discoloration in the water-conducting tissue supports the diagnosis, though other diseases can cause it too. For a simple screening test, suspend a freshly cut stem end in clear water; milky bacterial strands streaming from the cut suggest bacterial wilt. Drought, root damage, and fungal wilts can look similar, so the test is not conclusive; a diagnostic laboratory can confirm the cause. In cucurbits, check for cucumber beetles: their bacterial wilt is a different disease.

Prevention​

Start with healthy transplants and avoid moving soil or plants from affected beds. Clean tools, footwear, and containers after working around suspect plants, and keep potentially contaminated soil out of irrigation water. Improve drainage and water at the base of plants without splashing soil onto foliage. Avoid injuring roots when cultivating. Remove susceptible weeds that could harbor the bacteria. Where Ralstonia bacterial wilt has been confirmed, rotate to nonhost crops for several years, recognizing that rotation may not eliminate bacteria that persist in soil. Choose resistant varieties or grafted plants with resistant rootstocks where available; check that resistance covers local strains. Do not save seed or take cuttings from suspect plants. For cucurbits, managing cucumber beetles is especially important because they spread a different bacterial wilt.

Treatment​

There is no reliable cure once Ralstonia bacterial wilt infects a plant. First, check soil moisture and rule out a simple watering problem; avoid repeatedly watering already-moist soil. If bacterial wilt is suspected, remove the affected plant promptly, including as much of its root system as practical. Bag it for disposal rather than composting it at home. Do not move soil from the planting site to other beds. Clean soil from tools and footwear, then disinfect tools before using them elsewhere. Stop using any irrigation water suspected of carrying the bacteria, and monitor nearby plants. Do not replant a susceptible crop in the same spot that season. Copper sprays and ordinary fungicides do not cure an infection inside the plant. If the diagnosis is uncertain, contact a local plant diagnostic service before planning future crops; confirmed infections may call for resistant plants, crop rotation, or a different planting site.

Plants Affected​

Cucumber, Delicata Squash, Ginger

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