Here we are in another relatively wet spring. While this is great for our water resources and ecology, as the rains continue into spring it can bring problems to the garden. I am talking about diseases. Here in the San Joaquin Valley, we are fortunate to have a moderate climate that allows us a long and sometimes endless warm growing season and low humidity that relieves a lot of disease pressure. That won’t be the case this spring!


Due to the weather so far this spring we will see an unprecedented amount of disease infestation. Most of these diseases are ever present, they only attack when the conditions are right and we have the perfect storm (pun intended!). Unless precautions are taken to prevent damage or reduce at least, you will likely see diseases like rust, leaf spot, downy mildew, powdery mildew, fireblight (worse than normal), early blight and more. It would be wise to begin treating to prevent the diseases now. Here are the product recommendations:


Monterey Disease Control fungicide spray ready to use




Monterey Disease Control – Organic, curative or preventative. Can also be used as a soil drench for soil borne diseases. Best as a preventative. Introduces good bacteria to fight the bad guys. Sometimes stronger control is needed. Listed for ornamentals and edibles. No waiting period between spraying and harvesting. Ready the Ready to use label here.







Daconil fungicide spray ready to spray




Daconil – synthetic, curative. Only preventative for certain diseases, on certain plants. Listed for edibles but has a waiting period between spraying and harvesting. Read the Ready to use label here.







Monterey Neem Oil spray ready to spray bottle



Neem Oil – Organic for ornamentals and edibles. Very effective. Preventative or curative but better as a preventative in my opinion. Great for roses because it also kills insects and mites. Caution to be used when the weather is warmer than 85 degrees or so. It can cause leaf burn. Pictured is Monterey Neem oil but there are many other brands out there and on our shelf. Read the Monterey Neem Oil Ready to Spray label here.






Here is a quick (far from thorough!) list of plants and the diseases they are prone to. We would recommend keeping a sharp eye on them for symptoms and to treat preventatively:

  • Roses – rust, powdery mildew, downy mildew, black spot, leaf spot, bacterial blight
  • Lilacs – powdery mildew
  • Lawns – rust
  • Crape Myrtles – powdery mildew
  • Flowering Pears, edible Apples, Pears, Pyracantha, Hawthorn (Crataegus genus) – fireblight. Read more about fireblight here.
  • Hydrangeas – powdery mildew, Botrytis
  • Euonymous – powdery mildew
  • Snapdragons, Cosmos – powdery mildew, rust
  • Magnolia – powdery mildew, leaf spot
  • Camellia – petal and flower blight
  • Fruit trees (excluding citrus, pomegranates, Persimmons, Avocados) – Blossom brown rot, leaf spot, shothole, peach leaf curl, brown rot, scab, bacterial blight