Bacterial leaf spot of endive

Bacterial leaf spot of chrysanthemum (Pseudomonas cichorii) is a Gram-negative soil bacterium that is pathogenic to plants. It has a wide host range, and can have an important economical impact on lettuce, celery and chrysanthemum crops. P. cichorii was first isolated on endives, from which it derives its name.

Symptoms
Symptoms are varied and may include brownish-black lesions, light and dark zones on and a yellow halo around affected areas on leaves.

Prevention
Many disease-producing bacteria restricted to plant leaves can be controlled; however, prevention should be the aim. Provide plants with light conditions that are optimum for their growth. Sun-loving plants should get full sun, and all others should be placed near an east window or given supplemental lighting.

Avoid placing plants where there are conditions of high humidity, crowding, or poor air circulation. Do not mist plants and avoid wetting the foliage when watering, as bacteria need water to multiply and spread to healthy leaves. Water plants according to recommendations, being careful not to overwater them. Proper watering, repotting every 6 months to 1 year in fresh sterile soil, fertilizing every 8-12 weeks during the spring and summer, and controlling insect infestations will keep plants growing in healthy condition and lessen the likelihood of infestation by bacteria or other disease organisms.

Treatment
Should a plant become infected by bacteria, the following suggestions may help to halt the spread of infection. Provide conditions that are optimum for the plant's growth, as described above. Isolate the diseased plant and prune infected leaves, but avoid excessive handling of diseased plants. If more than one third of the plant is involved, prune infected leaves over a period of time, since removing too many leaves at one time will put the plant under further stress. Disinfect scissors before each cut by dipping them into a freshly made solution of 1 part Chlorox or Hilex bleach and 9 parts water.

If the disease is systemic and has spread throughout the plant, affecting the stems as well as the leaves, the plant cannot recover. We recommend destroying the plant to prevent spread of the bacteria to healthy plants.