Dealing with Powdery Mildew
A common complaint that has been affecting local gardens and greenhouses is powdery mildew.
Powdery mildew is a fungal disease that looks like a white or grey powdery patch found on the surface of a plants foliage or buds. It won’t kill the plant but it will certainly stress the plant and prevent proper photosyntheses to occur. Some plants are more susceptible to powdery mildew than others. Roses, Lilacs, Viburnums, BeeBalm, Cucumbers, Squash, and beans tend to get it first.
There are preventive steps that can be done to help minimize the problem.
Good air circulation is very important. If you have a greenhouse, make sure that the doors and vents are open during the day to keep the air moving. Ensure that plants are spaced apart and that there are no weeds. Keep plants staked and pruned. When pruning you want to keep the centre of the plant open as this will help with air circulation. Water plants in the morning so that the plants are dry by nightfall, and when watering try to avoid getting water on the plant. Soaker hoses and drip irrigation work well.
If a plant is affected by powdery mildew, remove the infected foliage immediately before it can spread, and destroy it. Do not put it into the compost as you don’t want the spores to spread. Clean your pruners or scissors that were used to remove the infected foliage with a mild bleach solution (one part bleach to four parts water). One nice thing about powdery mildew is that it won’t spread from one type of plant to another. If a rose has powdery mildew that strain of powdery mildew will not spread to the lilac, but it can spread to other roses if they are nearby.
There are products available at the garden centre that can help treat powdery mildew. Greenearth Bio-fungicide tomato & vegetable disease control will work. The active ingredient in it is Bacillus subtilis. Also available by ‘Greenearth’ is Garden Sulphur which comes in the form of a powder that is directly dusted on the affected area of the plant. Other products include a wettable powder called ‘Bordo Copper Spray’ or Safers ‘Defender’.
Jos Van Hage owns and operates two Art Knapp Home and Garden Centres in Prince George
- Highway 16 west at Kimball Road
- Highway 97 North at Northwood Pulpmill Road