Managing Powdery Mildew!

Powdery Mildew is a common disease that affect many different plants including vegetables, fruits, flowers, trees, shrubs and more.  This fungus grows best in warm and humid environments and it will overwinter in the soil in even the coldest temperatures. 

It is spread by insects, water run-off and wind.  If your plants are affected by powdery mildew there are many things you can do to stop it and prevent it from even happening. 

Identification

Powdery Mildew presents itself as white to gray spots on leaves that look like powder appearing on a portion of the leaf or the whole leaf and may extend to the stems, flowers and fruits.  More advanced stages of the fungus cause foliage to curl or turn yellow or brown.  The leaf may drop and flowers will be compromised.   The good thing about powdery mildew is that it is rarely fatal. 

Prevention

Preventative measures will certainly reduce the possibility of getting powdery mildew in your garden.  Here are a few that will keep the fungus away:

  1. Plants must have good air circulation around them.  Do not crowd them
  2. Plant vegetables, fruits and flowers where they get six hours of light each day and only plant those plants that are shade lovers in shade. 
  3. Over-fertilization can invite the fungus to attack your plants.  A slow-release fertilizer will go a long way in preventing powdery mildew because the young leaves on a plant are more susceptible.  Slow-release fertilizer controls growth better and you will not get a large quantity of new leaves all at once.
  4. Once you do get a case of powdery mildew, never use parts of the affected plant in your compost or as mulch.  Burn the debris from affected plants or put them in a garbage bag.
  5. Water the soil avoiding the leaves of the plants.  The disease tends to spread with water run-off.  Therefore, using soaker hoses near the base of your plants is better than sprinkling.

Erradicating

Even though you apply the above preventative measures, you can still get powdery mildew.  Several options are open to you to stop the fungus from growing but it is very important that the fungus be stopped before it gets too bad.  Always walk around your garden at least weekly to inspect leaves for any problems. 

Several items are found at the home and garden store that will stop a case of powdery mildew as follows:

  • Green Cure Fungicide is a solution of potassium bicarbonate and can keep plants free for 2 weeks before it needs to be reapplied.
  • SERENADE is another fungicide that works well and it is also approved for organic gardens.  It is so safe you can treat a crop and pick it in the same day.
  • A fungicide that 100% food-grade ingredients that gets rid of fungal problems quickly and safely is SNS244 or Zero Tolerance Herbal Fungicide.  Both are easily found in home and garden stores, especially those that cater to organic gardeners.

Natural Control

Several things you find in your kitchen or bathroom will also treat a case of powdery mildew.

  • Baking soda is one of the best things for powdery mildew, but must be used during the very early stages for it to be effective.  Mix 1 tablespoon of baking soda with 1 teaspoon of insecticidal soap and 1 teaspoon dormant oil to 1 gallon of water and spray on leaves every 1 to 2 weeks depending on rainfall.  The pH of the baking soda kills the fungus.  It is best to apply in the early evening because the liquid can cause the leaves to sunburn.   
  • Potassium bicarbonate is like baking soda but is a fungicide.  It gets rid of the spores of powdery mildew even when it has started to spread.  Another use for potassium bicarbonate is as a leavening agent when used to make wine.  Therefore, you can find it wine making supply stores.  Mix 3 tablespoons with 3 tablespoons vegetable oil and ½ teaspoon insecticidal soap in 1 gallon of water and spray once or twice a week. 
  • Vinegar is acidic and acid controls powdery mildew.  Add 3 tablespoons apple cider vinegar to 1 gallon of water.  Spray sparingly because the acid in the vinegar can burn the leaves.  Re-apply every 3 to 4 days.
  • Milk has been known to control powdery mildew but no one really knows why.  Some say the milk boosts the plants immune system.  It produces free radicals that fungus does not like.  Spray bi-weekly a solution of 1 part milk (2% milk works great) to 2 parts water.
  • Garlic is good for many things and getting rid of powdery mildew is one.  Crush 6 cloves of garlic and add to one ounce of neem oil and 1 ounce rubbing alcohol.  Let this stew for two days and strain.  Collect the crushed garlic and soak it in 1 cup of water for a day.  Strain and get rid of the garlic and mix the two solutions with 1 gallon water.  Spray only the leaves once a week.
  • Neem oil comes from a tree that grows in India and it is proven to control diseases and fungus.  The way it works is that it changes the metabolism of the plant and spores of the powdery mildew cannot grow.  Mix 3 tablespoons of neem oil in 1 gallon of water and only spray on leaves.  Do this in the evening because this solution can cause the leaves to sunburn too. 

Prevention is the best bet to stay clear of powdery mildew, but if you get a case, do not fret.  It will not kill your plants and it will not spread to other species of plants.  It can be controlled with store-bought, organic approved solutions or opt for a natural solution like baking soda or vinegar.