Powdery Mildew: signs & treatmentsUpdated 2 years ago
Signs
- Tan to brown scabbing or cracking on the leaves
- White powder, or whisps, around the cracks
- Pale splotches form before the cracks appear
Although powdery mildew is a very common plant disease, it presents atypically on succulents. On succulents, the cracks form first and commonly exist without, or with only very faint powder. It can appear like a bacterial infection in this way.
Treatments
- An over the counter fungicide works well. Copper based fungicides are particularly effective
- Proper watering and low humidity prevent the spread of the disease
- Removing obviously infected leaves is a must. After all, the scabs will never go away, even after the fungus is killed
- A foliar spray of a 1:1 water to whole milk solution, applied when the plant is getting the most sun, has been shown to be very effective against powdery mildew. Check the links below for relevant research
Please note, hard water stains can appear like powdery mildew. Note the Tylecodon below.
Just remember, hard water will rub off fairly easily and will never leave any scabbing.
Milk Treatment Research
- Bettiol (1999) found high concentrations of milk treated powdery mildew on zucchini better than conventional fungicides (fenarimol and benomyl)
- Nam et. al. (2005) found that a 10% concentration of milk sprayed on strawberries prevented fruit from becoming soft due to powdery mildew
- Crisp et. al. (2006) Used electron microscopy to see powdery mildew hyphae get destroyed within 24 hours of being treated with milk and whey. They believe oxygen radicles produced by milk when exposed to sunlight caused this damage