| There's no simple answer. The fungal spores can be carried in the wind. Moderate temperatures of 60? to 80?F and shady conditions generally are the most favorable for powdery mildew development, but it can attack in full sunshine, too. Powdery mildew spores and mycelium are sensitive to extreme heat and sunlight, and leaf temperatures above 95?F may kill the fungus. You can use a fungicide to help prevent the disease or you can mow over your vinca (with the highest setting on your mower) to remove the diseased plant parts. |
