Field Guide     Crop Diseases     Bacterial Leaf Blight

Bacterial Leaf Blight

CROPS IMPACTED: Rice, soybean, cassava, beans, cotton, tomato, pepper, carrot, and other secondary host crops

Bacterial Leaf Blight

Family: Xanthomonadaceae

Bacterial Leaf Blight Bacterial Leaf Blight

About Bacterial Leaf Blight

Life Cycle

Many forms of bacterial leaf blight are seedborne, and are able to survive for long periods of time in this way. The bacteria are also able to survive in plant debris, but not in soil alone. Seed allows for the spread of bacteria, while rain and sprinkler irrigation helps the disease develop further. Wet conditions and splashing water distribute bacteria amongst surrounding plants. Bacteria will initially appear in the mid to upper parts of the canopy, and then it will spread throughout the plant, possibly affecting leaves, pods, and fruits. The disease will likely be seen early on in the season while seedlings are beginning to develop. Once infected, the bacteria will affect all growth stages of the plant. In many cases, premature defoliation will occur, leaving the plants’ fruit vulnerable to direct sunlight. Ultimately, this can lead to substantial yield loss, so long as the bacteria are able to fully occupy the plant.

Bacterial Leaf Blight Identification and Habitat

Identification

Bacterial leaf blight can breakout on any aerial part of the affected plant. For the most part, bacteria are identifiable through brown spots scattered on leaves. Leaves will often have many lesions which eventually coalesce. These brown areas will appear water-soaked with a yellow border. Often the areas will be dried out and may have some bacterial discharge. In some plants (e.g. cotton), the affected areas will have a red or brown border that slowly turns black. These areas may appear as spots or streaks on the leaves. Bacteria will usually appear on the parts of the plant that receive the most water and moisture. In severe cases, defoliation can occur rapidly, causing heavy exposure of the plant.

Varieties

  • • Bacterial leaf streak
  • • Bacterial leaf blight

Habitat

Conditions with warm temperatures, high humidity, and plenty of rain are ideal for the development of bacterial leaf blight. However, conditions that are overly dry and hot do not favor the development of the disease. Bacteria will have a hard time infecting plants in temperatures below 65°F. Temperatures ranging from 77°F to 86°F are most suitable for the development of bacteria. Overcrowded crops facilitate the spread of bacteria from plant to plant because they lack good air circulation and sunlight to help keep plants at proper moisture levels. Overhead irrigation will also help the spread of bacteria. Sprinkler irrigation also makes it more likely for bacteria to be dispersed amongst plants.

Bacterial Leaf Blight Management and Control Methods

Cultural Control

First, to avoid bacterial leaf blight, use disease-free seeds and planting materials. Once an infected seed is planted, spread of the disease will happen quickly, making it very important to plant healthy seeds. Crop rotation with other crops that are less susceptible to the bacteria should be considered. This can be an effective way to stop the bacteria from developing on crops. After seeds are planted, managing water and properly fertilizing is necessary. Since bacteria spreads through water, try to water at the base of plants so that there is minimal splashing between plants. Good soil drainage can also help reduce the spread of bacteria through water sources. Be sure to space plants effectively so that they have good air circulation and sunlight distribution. When working with crops, try to allow crops to dry out before handling them to avoid spreading bacteria from plant to plant. At the end of the season, properly dispose of infected plants so that there is no chance of bacteria occupying the field.

Chemical Control

Although there are not many chemical controls for Bacterial leaf blight, the use of insecticides can be effective in reducing the spread of bacteria. Insects feed on infected plants and carry bacteria to non-infected plants, making insecticides a useful option. Before using insecticides, read labels for cautionary advice and application guidelines.

Alternative Bacterial Leaf Blight Names

  • • Bacterial blight

Sources

http://www.ipm.ucdavis.edu/PMG/r102100811.html

http://www.oisat.org/pests/diseases/bacterial/bacterial_leaf_blight.html

http://www.extension.umn.edu/agriculture/crop-diseases/soybean/bacterialblight.html