Powdery mildew is one of the most easily recognized and identifiable of all plant diseases. Powdery mildews are also recognized to attack a wider variety of plants than any other plant disease. The symptoms are characterized by the presence of whitish, powdery thread-like growth on the surfaces of leaves, stems and often flower petals. Infection by the powdery mildew fungus seldom kills affected plants, although it can cause foliar distortion, defoliation, inhibit growth and weaken the health of the plant.
Powdery mildew obviously reduces the aesthetic appeal and value of a plant. Cut flowers or indoor potted plants can be affected with powdery mildew. Powdery mildew will continue to thrive and spread on cut flowers, thus a small infection will continue to expand. Powdery mildew can be very severe on roses, phlox, lilac and bee-balm in particular, but can infect nearly any plant.
Moreover, spores released from the powdery mildew on plants in the home or garden may cause respiratory discomfort since the powdery mildew spores are easily dislodged and carried by air currents. In recent years the effects of mold and mildew have become more well known and allergies and respiratory health issues associated with mold and mildew are a real concern. Mold spores are incredibly small and usually not visible with the naked eye. If you can easily see mildew it means you are looking at tens of thousands of spores or more.
Causes of Powdery Mildew Infestation: Mold and mildew spores are all around us and abundant in a garden. They take hold and thrive when conditions are beneficial to their growth. The environmental conditions which are most favorable for disease development are cool night temperatures (about 60 F) with high humidity (90-99%) and warm day temperatures (about 80 F) with humidity of 40-70%.
Mildew Prevention: Since we typically can't control these environmental conditions, good growing practices can aid in control of powdery mildew. We'd all like to have abundant sunshine, but often we want to have plants grow in areas that are less than optimal. Some measures to help reduce the likelyhood of powdery mildew include watering plants early in the day to allow moisture on plant leaves to dry prior to sunset. Spacing plants allows ventilation through the foliar canopy. GreenCure® can be used as a good preventative control of powdery mildews by applying 1 tablespoon per gallon of water every 1 to 2 weeks when environmental conditions are ideal for the disease. (See How To Use Instructions) Preventing an infestation by using GreenCure® will help you maintain healthy, vibrant plants.
Mildew Infestation Control: In cases of moderate to severe infestation, such as shown in the picture above, GreenCure® can be used to eradicate powdery mildews by spraying plants completely with a mixture of 2 tablespoons of GreenCure® per gallon of water weekly for 3 weeks followed by the preventative program thereafter. GreenCure® kills mold / mildew spores within seconds of contact by causing an immediate dehydration of the spores and destruction of the cell walls. Many of the deceased spores will slough off or be washed away with the next rain or watering. In most instances, leaves can recover, however as with any wound, scars and discoloration can remain. If you prune infected leaves, stalks or branches, they should be disposed of in the trash, because composting will not kill the mold spores.
A rose infected with powdery mildew
High-speed photography captures mold spores blowing off a rose leaf
This microscopic view shows live mold spores (above) and the same spores destroyed by GreenCure®