Prevention of Powdery Mildew on Tuberous Begonias

June 25 2015 | Posted in Begonia Care, Begonia Diseases, Begonia Tips

Prevention of Powdery Mildew on Tuberous Begonias

Prevention of ??powdery mildew or treating powdery mildew on tuberous begonias is a subject of great interest with begonia growers. Basically it comes down to prevention. Powdery mildew is in the environment and begonias are susceptible to it. Luckily there are plenty of non-toxic ways to prevent powdery mildew and if needed some chemicals as well.

Good Cultural Practices:

1. Start with good clean free draining potting soil. Plants are healthier in good soil. An unhealthy weak plant is more susceptible to powdery mildew.
2. Good air flow is necessary. Do not crowd plants for many reasons.
3. Do not over fertilize. Powdery mildew spores germinate best on new succulent growth. Slow release ok.
4. Give plenty of light; moisture and shade incubate powdery mildew. Begonias grow better in bright filtered light anyway. Unfortunately full sun all day is not possible, but some sun is better than none.
5. Some varieties can be??more susceptible.

Green Preventatives: Spray these once every couple of weeks. They are preventatives, not cures.

1. Any milk ??? at 2 to 3 parts water to 1 part milk is effective.
2. Neem tree oil – coats leaves preventing germination of spores. 2 tablespoons per gallon
3. Horticultural oils – does the same coating process. One teaspoon per gallon.
4. Baking Soda – 1 tablespoon per gallon. Careful, burning can occur especially when mixed with horticultural oil.
5. Copper sulphate & calcium hydroxide; AKA: Boudeaux Mix. Is somewhat toxic.

Following not trialed on begonias.

6. Potassium bicarbonate ??? like baking soda, but may actually eliminate fungus spores.
7. Mouthwash ??? Generic ethanol based mouthwash. 1 part to three parts water.
8. Vinegar ??? 2-3 tablespoons of Apple cider vinegar mixed in 1 gallon of water. May burn.
9. Soaps ??? Safers Insect soap and many other brands.
10. Sulfur ??? Safer Garden Fungicide, Bonide Sulfur Plant Fungicide. Must use more often.

Chemical Prevention:

1. Chlorothalonil; Trade names: Ortho MAX, Bonide Fungonil, Gardentech Daconil, Bravo, Echo
2. Triforine; Trade names: Funginex, Ortho Rose Pride
3. Triflaxystrobin & Triadmefon: Trade names: Strike (was Bayleton)
4. Tebuconazol; Bayer Advance Disease Control
5. Miclobutanil; Immunox

Use all with protective clothing and follow direction on labels.