How do I prevent mold from growing on my phlox?

Beth
by Beth

I'd like to get rid of this problem once and for all or be able to treat the soil in some way before it ever blooms. When I start spraying it with fungicide on the plant the plant looks really bad.

  3 answers
  • Lee henry Lee henry on Feb 21, 2019

    gardeners will tell you to get more air though the plant by pruning the interior stalks doing this early will also make larger blooms

  • Lynn Sorrell Lynn Sorrell on Feb 21, 2019

    Powdery mildew is really more of a cultural problem, caused by higher humidity and poor air circulation. Powdery mildew also thrives in shaded, damp locations.The fungus is host specific and doesn't stay in the soil, but clean-up in the fall of your vegetable garden is always recommended. There are both cultural and chemical controls listed. Baking Soda (sodium bicarbonate) -This is possibly the best known of the home-made, organic solutions for powdery mildew. Although studies indicate that baking soda alone is not all that effective, when combined with horticultural grade or dormant oil and liquid soap, efficacy is very good if applied in the early stages or before an outbreak occurs.Use this recipe to make your own solution—mix one tablespoon of baking soda with a teaspoon of dormant oil and one teaspoon of insecticidal or liquid soap (not detergent) to a gallon of water. Spray on plants every one to two weeks.Potassium bicarbonate– Similar to baking soda, this has the unique advantage of actually eliminating powdery mildew once it’s there. Potassium bicarbonate is a contact fungicide which kills the powdery mildew spores quickly. In addition, it’s approved for use in organic growing.Mouthwash – If it can kill the germs in your mouth, certainly the fungal spores of powdery mildew are no match. And that’s the premise. Generic, ethanol based mouthwash can be very effective at control. Tests using one part mouthwash to three parts water worked for well for Jeff Gillman, Ph.D and Associate Professor at the University of Minnesota, Department of Horticulture. Just be careful when mixing and applying mouthwash as new foliage can be damaged.Vinegar – Similar to mouthwash, the acetic acid of vinegar can control powdery mildew. A mixture of 2-3 tablespoons of common apple cider vinegar, containing 5% acetic acid mixed with a gallon of water does job. However, too much vinegar can burn plants but at the same time, higher concentrations (above 5%) are more effective.Sulfur and Lime/Sulfur – Direct contact by sulfur prevents disease spores from developing. When mixed with hydrated lime, the solution will penetrate leaves for even greater effectiveness. A widely available version of this combination includes copper sulphate and hydrated lime, known as Bordeaux mix. However, all of these solutions can burn plant tissue and is damaging to microorganisms in the soil and harmful to beneficial insects. It is also considered moderately toxic to mammals and humans. Use sparingly and with caution if at all.Milk – The latest player in the fight against powdery mildew is milk. It’s not clear yet why it works so well, but it is believed that naturally occurring compounds in the milk are at work to combat the disease while also boosting the plant’s immune system. One experiment showed good results by applying a weekly dose of one part milk to two parts water.Water – Ironically, dry conditions and high humidity are the most favorable conditions for powdery mildew to form. But straight water is its enemy because it washes off the spores before they have time to embed. However, water isn’t something that I promote for control because wet foliage is friend to many other plant diseases. If you’re going to try this option, do so early in the day so foliage has time to dry out quickly.Neem oil – This is a readily available organic option to disease and pest control. Neem oil is extracted from the neem tree, native to India. This is an effective disease control and a broad spectrum, natural insecticide that is kinder to beneficial insects and mammals. As for controlling powdery mildew, results vary but it is not the best option. Results are usually moderate at best.Even with many choices for control, prevention is still the best medicine, not only with powdery mildew, but with other diseases as well.