Powdery Mildew

July 27, 2014 by  
Filed under Answers and Tips, Fungicide, Garden Care, Plants, Vegetables


Does your squash look like this?

Your squash plants have powdery mildew.  It can be a chronic late summer and fall disease in the vegetable garden.  It is unattractive and it can affect the flavor and reduce yields of some fruits and vegetables.  It has a dusty flour or talcum powder-like appearance on the surface of the leaf.

Powdery Mildew also affects:  beebalm, lilacs, zinnias, roses, garden phlox, beans, cucumbers, grapes, and melons.


Powdery mildew can be prevented, and it can be controlled.  The key to preventing is to grow your squash in open, full sun locations, where they will have good air circulation, and exposing as much leaf surface as possible to direct sunlight, which inhibits spore germination.  We also recommend ground applied (drip) watering rather than overhead sprinkling, and watering in the morning rather than evening to take advantage of sunshine that quickly dries the leaves.


To control powdery mildew, pick off affected plant parts and bag them tightly and put them in the trash.  Then we recommend using one of the following:

1. Fertilome Triple Action is a fungicide, insecticide, and a miticide.  An  effective fungicide for the prevention and control of various fungal diseases including powdery mildew, blackspot, brown spot, dollar spot, anthracnose, rust leaf spot and many others listed on the label.  It also controls aphids, spider mites, scale, mealybugs, beetle, leaf miners, leaf rollers, army worms, webworms, weevils, tent caterpillars, white flies, and many more listed.  Contains pyrethrins.  Can be applied every 14 days as prevention.  May be applied up to day of harvest.

2.  Fertilome Broad Spectrum is fungicide that will control all fungus.  Spray until the point of runoff and repeat at 7-14 day intervals.  May be applied up to day of harvest.

3.  Safer Garden Fungicide.  If organic gardening is your thing, this is the fungicide for you.  Spray at first sign of infection and repeat at 7-10 day intervals.  May be applied up to day of harvest.

Now that’s ‘advice you can grow with’!