Powdery Mildew

Powdery Mildew is a group of fungi with the common symptom of a grayish-white, powdery mat visible on the surface of leaves, stems, flower petals and fruit. Although it is not considered fatal, continued infestation weakens the plant and can make it susceptible to other issues.




This disease is most severe on plants in the shade or areas where there is poor air circulation. It really likes cool temperatures with high humidity, but it can be seen in warm, dry conditions and in full sun.  Powdery mildew can affect many plants, but it tends to be very host specific, so mildew on your yard will not infect your viburnum.

Some common plants that can become infected:

    • Trees: ash, birch, buckeye, elm, linden, maple, oak. 
    • Fruits: apple, grape, crabapple, blueberry, pecan.
    • Shrubs: lilac, cotoneaster, dogwood, azalea, crape myrtle, euonymus, rhododendron, spirea, viburnum, roses.
    • Flowers: phlox, snapdragon, dahlia, zinnia, delphinium. 
    • Vegetables: cucumber, squash, pumpkins, beans, eggplant, lettuce, peas, peppers, tomatoes. 
    • Turf: It infects over 1,000 types of plants.

Powdery Mildew Control

Universities suggest first to get mildew resistant varieties of plants but if you already have powdery mildew, it is to late for that.  Next they suggest pruning and thinning plants to improve air flow and allow more sunlight into the area.  Finally they say don't over fertilize causing lush growth, this is why many universities suggest fertilizing trees and shrubs in the fall after leaves drop or turn color, these nutrients are slowly used by the plant, not causing a burst of growth.

Products For Powdery Mildew Control

Trees, Shrubs and Flowers

ferti•lome Liquid Systemic Fungicide used early on is a great preventer.
ferti•lome F-Stop is another systemic that is very effective on powdery mildew. 
Many universities suggest if the infestation is severe, alternate between products, so spray one then 2 weeks later spray the other until weather conditions improve.  A non-chemical choice is ferti•lome Triple Action.

Fruits, Berries and Vegetables

ferti•lome F-Stop is the most recommended with ferti•lome Triple Action or ferti•lome® "Green" Label Copper Fungicide next.  Again, under heavy pressure choose two and alternate.


ferti•lome F-Stop Granule is the strongest fungicide available to homeowners so this is a great choice.  If applied early enough, one application will be enough.  If infestation is heavy, alternate with ferti•lome Liquid Systemic Fungicide



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