Cucumber
Bacterial Wilt of Cucurbits
Erwinia tracheiphila
Bacteria
In a Nutshell
- Wilting of plants.
Cucumber
Symptoms
Bacterial wilt in cucumbers usually begins from the upper leaves. These leaves start looking less bright and might get brown edges as the disease gets worse. The affected plants will wilt during the day but can recover overnight. To check if it's bacterial wilt, look for the insects that spread it: striped and spotted cucumber beetles. Also, if you gently pull apart a stem cut from a wilting leaf, you might see slimy threads from the bacteria. However, the absence of this slime does not necessarily indicate that the plant is uninfected, but its presence is strong evidence.
Recommendations
Organic Control
If a few plants show signs of disease, remove and bury them to stop the disease from spreading. You can also plant trap crops, which are types of cucurbit plants that pests find very attractive. These trap crops can distract pests from the plants you intend to harvest.
Chemical Control
Remember, once bacterial wilt infects a plant, controlling the disease directly is not possible, so prevention through beetle management is key. If you find two cucumber beetles on at least a quarter of your plants in an early stage you should consider using an insecticide. When plants are older, the threshold increases to eight beetles per quarter of the plants. It's important to remove any plants that show signs of bacterial wilt to stop beetles from infecting healthy plants. Ensure a light, homogeneous coating of the insecticide over the entire plant, paying extra attention to where the stem comes out of the soil and the undersides of leaves where beetles tend to hide.
What caused it?
Bacterial wilt, especially common in cucumbers, is caused by a bacterium that is spread by specific insects—the striped and spotted cucumber beetles. These beetles carry the bacteria in their stomach through the winter. They become infected by feeding on diseased plants, then pass the bacteria to healthy plants when they bite into them. Once the bacteria enter a plant, they grow rapidly and block the plant’s vascular system, causing the plant to wilt. This bacterium cannot be spread through seeds, does not live in the soil, and only stays in dead plant material for a short time.
Preventive Measures
- To prevent bacterial wilt in cucurbits, it's essential to manage cucumber beetles effectively.
- Check your garden at least once a week for these beetles, and look more often if you see any.
- Focus on the undersides of leaves, where these bugs like to hide.
- Keep a close eye on plants that wilt during the heat of the day and don't recover by the next morning, as this is a common symptom of bacterial wilt.
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