Question
I worked as an agricultural pest control tech in CA for 7 years.  I've found white spots on my 10 ft jasmine tree and suspect powdery mildew.  Where do I get a good fungicide or oil to treat the plant.  Also could this be another disease?  I'm a little rusty - wished I would have stayed in the business and up to date with the seminars....Thank You...

Answer
Sounds like powdery mildew.  Powdery mildew fungi belong to the group of plant pathogens called obligate parasites. Plant pathogens within this group can only grow and reproduce on or in a living host plant and can infect any green tissue; thus, powdery mildew may be found on leaves, green stems, and flower parts.

This fungus lives largely on the outer surface of the host plant. It has a high demand for the nutrients necessary for growth and spore production. It obtains these from host plant cells by means of small, root-like organs, called haustoria, that feed within the epidermal layer of the host plant.


Although powdery mildew rarely kills a plant, infection reduces host vigor and lowers aesthetic value.  

This can be prevented if the gardener understands the nature of the disease, learns to recognize early symptoms, and conscientiously applies preventative control measures.

As symptoms continue to develop, much of the leaf surface becomes covered by the grayish-white mildew , and the leaves are twisted or distorted. The coating of the leaf by the mildew reduces the leaf surface area available for photosynthesis.


Several fungicides (Table I) can be used to control powdery mildew. It is a good idea to use a different fungicide each season or alternate between different fungicides during the growing season. This is done to prevent the development of fungicide resistance in the natural powdery mildew population.

Table I. Fungicides for control of powdery mildew of roses:
  Banner MAXX? Immunex?
  Benomyl? Benlate
  Folpet? Phaltan
  Bayleton? Strike?Triadimefon
  Funginex? Triforine
  Triact? Rose Defense? Neem oil
  Pipron?
  Phyton 27? copper sulfate
  Rubigan AS?
  Cooke's?wettable, Safer?Garden Fungicide, Microthiol Special?Sulfur  

Check with your local garden type store for these fungicides.