Lettuce, like other vegetables, is unfortunately plagued by diseases from time to time. Find out below what diseases lettuce can suffer from, how you can recognize them and what you can do about them.
What diseases can affect lettuce and how do you recognize them?
Lettuce can be affected by downy mildew, lettuce blight and various viruses. Downy mildew appears as yellow-brown spots on the upper side of the leaves and white-greyish spores on the underside of the leaves. Lettuce rot manifests itself as rotten spots on the underside of leaves.
These diseases occur in lettuce
The most common disease affecting lettuce is downy mildew. However, lettuce can also suffer from lettuce rot and various viruses.
Downy mildew
Downy mildew can only be treated if it is discovered in time. If there is a severe infestation, the affected lettuce should be removed immediately to prevent the disease from spreading.
Causes of downy mildew
Downy mildew occurs when the weather is constantly too humid and the leaves lie directly on the wet ground.
Identifying downy mildew
Lettuce affected by downy mildew shows yellow-brown spots on the upper side of the leaves and white-greyish spores on the underside of the leaves.
Prevent and combat downy mildew
- Prevent too much moisture, if it rains for a long time, raise or ventilate lettuce with brushwood or something similar
- stick nitrogen avoid fertilization
- remove diseased leaves
- Treat infected lettuce with a decoction of onions, garlic and horsetail
Lettuce rot
Lettuce rot is usually a mixture of different infections and is also due to too much moisture. Symptoms are rotten spots on the underside of the leaves. The measures are similar to those for downy mildew:
- cut away diseased leaves
- Provide better ventilation, avoid moisture
- Lime if the pH value is too low
Preventing diseases
Most diseases are caused by excessive moisture and a weakened plant. As a preventative measure, you should generally:
- Observe crop rotation (only plant lettuce in the same place every three to four years)
- ensure adequate ventilation
- Remove weeds regularly
- don’t water too much
- Avoid waterlogging
- possibly lime if the pH value is too low
- don't plant too close together
Disease-resistant lettuce varieties
If you have struggled with diseases on your lettuce in the past, you will probably be happy to know that there are resistant varieties. The early 4-season varieties Dynamite and Merveille are particularly resistant to viruses and diseases. An overview of other early, middle and late varieties can be found here.
