Tobacco
Wildfire
Pseudomonas syringae pv. tabaci
Bacteria
In a Nutshell
- Brown, dead spots mainly on the leaves.
- Spots are usually surrounded by a yellow halo.
- Wilting, yellowing and dropping of infected leaves.
- Slowed or no more crop growth.
Can also be found in
Tobacco
Symptoms
The symptoms can develop quickly. Spots mainly appear on leaves but can also occur on stems, flowers, and tobacco fruit capsules. Spots are usually surrounded by a yellow halo. The spots start as small, pale-green circular areas, which turn brown in the centre due to tissue death. Spots can merge. In serious cases, the damaged parts of the leaves fall away, and only the leaf veins are left. Wildfire can affect the crop at any stage of growth, including seedlings in the nursery.
Recommendations
Organic Control
Alternative options for control of Wildfire are limited to the use of preventive measures and good field practices.
Chemical Control
Controlling the pathogen may involve applying copper-based chemicals, like Bordeaux mixture, during the early stages of plant growth. In areas where agricultural use is approved, the antibiotic streptomycin can be considered as an alternative. However, the effectiveness of streptomycin may be compromised as bacteria can rapidly develop resistance to it. When using pesticides or any chemical product, it is important to wear protective clothing and carefully read the label instructions. Regulations vary by country, so ensure you follow the specific guidelines for your area. This guarantees safety and increases the chances of successful application.
What caused it?
The bacterium that causes disease thrives in warm and moist conditions, often spreading after rainstorms. The wind plays a big role in how and where the disease moves. Watering plants with sprinklers can also spread the bacterium in a similar way. The bacterium can enter tobacco plants through natural openings or cuts made by insects. Once inside, the bacterium grows and spreads within the plant. As the plant begins to rot and die, the bacterium is released back into the environment, where it can infect other plants or stay in the soil for up to two years. The bacterium can also move to new areas through infected plant waste, soil, or farm tools.
Preventive Measures
- Start with healthy seedlings to minimise the risk of introducing the bacterium early on.
- Keep the field clean and free of debris that may hide the bacterium.
- Avoid overwatering crops as high moisture levels favour the disease.
- Manage insect populations to reduce the risk of the bacterium being spread through cuts made by insects.
- Check your crops often for any signs of disease, especially after it rains.
- Remove and destroy any infected plant material to prevent the spread of the bacterium to healthy plants.
- Rotate crops to prevent the build-up of the bacterium in the soil.
- Do not plant tobacco in the same field for at least two years after an outbreak of the disease to help ensure the bacterium does not persist in the soil.
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