These are a range of fungal diseases that attack a wide range of plants including roses and crepe myrtle and many fruit and vegetables including apples, grapes, zucchini and silverbeet. Spores are carried by wind and rain. Depending on the pathogen either warm, humid or warm and dry weather may favour the spread of these diseases. Fungal spores are easily dispersed by rain and wind, then landing on the leaves and causing the infection. Powdery mildew is easily recognised as it appears as a dusting of white powder on leaves, stems or buds.
To reduce the risk of powdery mildew, avoid watering the foliage of the plant (water to the soil only). Also use disease-free plants and seeds and selectively prune all plants to help ensure there is sufficient spacing between plants to allow good air movement. When pruning ensure to sterilise secateurs and pruning tools between with bleach between plants to prevent the disease from spreading.
Preventative spraying including milk sprays (one part full cream milk or milk powder to nine parts water) may delay the disease. Spray with Sharp Shooter Lime Sulphur during winter when trees and plants are dormant and especially after pruning.
Once the disease is present remove affected leaves, flowers or the entire plants. Powdery mildew on ornamental plants may be treated with a fungicide spray such as EarthCare Rose Black Spot & insect spray. When spraying the foliage follow the directionS on the back of the pack and spray both sides of the foliage. Repeat applications maybe needed for further control. Remember not to spray when beneficial insects and bees are around.