Powdery Mildew Treatment

Tips on Powdery Mildew Treatment

Gardening is a cause for pride and satisfaction with lush, green plants; however, when those plants show evidence of an infection of powdery mildew, treatment must be swift to avoid widespread infection.

What it is

Mildew is caused by fungus.  As are most types of fungi, mildew is most likely to develop when conditions are right, with high humidity.  This means that, in most parts of the country, it occurs later in the growing season.  When plants are placed too closely to others, the problem can be exacerbated by fostering a condition that favors retaining the humidity within the plants’ leafy interiors.

The fungus can occur on virtually any type of plant.  Fruit trees, flowering shrubs and vegetable plants are equally as susceptible to becoming infected.  Trees in surrounding areas can develop mildew and infect your garden through the spread of spores.  Breezes that filter through the leaves carry the spores which drop in various areas, including the plants in your garden.  However, there are many different varieties of mildew fungus, each of which is specific in the types of plants that they affect.  Species that affect flowering plants will not affect fruit trees, for example, or vice versa.

A major issue with plant mildew is that it is not eliminated by a killing frost or the successive snowfall of winter.  If the infected plants or fallen leaves from infected trees were tilled into the soil, the spores of the fungus will simply winter over and emerge the following spring with the onset of warm, moist weather.  Spores once again become airborne, settling on leaves of different plants to start the cycle over again.

How mildew affects plant life

Mid to late season is when evidence of the mildew appears.  White patches become visible on the green leaves, splotching otherwise healthy plants.  Soon, the leaves will yellow and begin to die off and drop as the essential nutrients the leaves require are depleted.  Allowed to continue, the infection will spread to the remaining leaves on the plant as well as surrounding plants.  The leaves may appear malformed and stunted; buds and developing fruit will bear this same affliction.

Powdery mildew treatment

The best method for dealing with powdery mildew is through the use of fungicides, but it is a serious and meticulous process.  Choosing the proper fungicide will require careful selection, as not all fungicides are designed to be used on all types of plants.  Some fungicides to review are sulfur, potassium bicarbonate, triforine and triadimefon.  It cannot be stressed enough to completely read the package instructions to ensure that only those fungicides that are able to be used on food plants are chosen if those are the affected plants; many of these products are toxic.


If only one or two plants are affected by the mildew, removal of these plants may be the best course of action.  In doing so, the gardener must be careful not to spread the spores.  Pruning away diseased leaves and stems may be all that is needed in some cases.  Always collect the affected foliage and remove to prevent spreading the infection.


There is no way to complete avoid the fungus spores, but it is possible to make your garden more resistant.  Choosing plants that are naturally resistant to powdery mildew, proper spacing of plants, morning watering and planting in full sun locations are all methods for preventing the mildew.  A homemade spray of 1 teaspoon baking soda, 1 quart water and two to three drops of liquid soap that is applied to the both the underside and tops of leaves of the plants once each week can make the leaves uninviting to the spores.

The pride felt when a garden or landscape displays lush, green foliage is well worth the work it takes to achieve it, and early powdery mildew treatment will keep the remaining plants healthy and free of infection.