- The best way to prevent black rot is to ensure proper growing conditions of the persimmon tree. Persimmons require full sun and well-draining acidic soil with a pH between 5.8 and 6.5. They are drought-tolerant trees but grow best when deeply irrigated once every 10 days. Avoid the spread of black rot disease after infection occurs by removing infected parts of the persimmon tree immediately.
- Bordeaux mix is a combination of hydrated lime and copper sulfate, and it is effective against black rot by preventing the spreading of the disease and new outbreaks. Apply Bordeaux mix to persimmon trees that were previously infected with black rot right before and immediately after the flowers bloom. Apply Bordeaux mix properly to avoid plant burn. Don't use when temperatures are below 50 degrees Fahrenheit or when humidity is high.
- Bicarbonate has fungicidal properties that may kill black rot organisms. Potassium bicarbonate is most effective at controlling and preventing the persimmon disease, but a homemade mixture of sodium bicarbonate (baking soda) also has a beneficial effect. Make a baking soda homemade fungicide by dissolving 1 teaspoon baking soda in 1 quart warm water. For best results, start applying the persimmon fungicide before symptoms appear, but conditions for the disease are right. Apply the solution out of direct sunlight and cover the persimmon tree thoroughly. If the solution is too concentrated, the persimmon tree may burn.
- Bacillus subtilis is a bacterium that either kills or creates inhospitable living conditions for black rot pathogens. When applied to the persimmon tree, the Bacillus subtilis bacterium vigorously takes over the food and living resources, leaving nothing for the black rot pathogens to survive on. No harmful effects on people, animals, insects or plants are caused by Bacillus subtilis. Because the fungicidal protein breaks down quickly, reapplications of the persimmon fungicide are necessary once a week.
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