Verdia · Library
Downy mildew observations
Compare upper-leaf discolouration with growth underneath, and see how Verdia routes Peronospora, Plasmopara, Bremia and four other genera to downy mildew.
How Verdia recognises a downy mildew name
The downy mildew group in Verdia is built from seven genera: Peronospora, Plasmopara, Bremia, Pseudoperonospora, Hyaloperonospora, Sclerospora and Albugo. The app compares the first word of the scientific name returned by Pl@ntNet with that list. When the genus is unknown, it falls back to the words peronosporaceae and peronosporales anywhere in the name. A result that matches neither shows no care steps.
The group is kept apart from powdery mildew, which has its own genus list and its own steps. A white coating alone does not tell you which list a name will fall into.
Building a useful observation
- Photograph the same leaf from above and from below, so the discoloured area and any growth underneath are both visible.
- Record the host plant's name and which leaves show the change, older or newer.
- Note recent wet conditions, because prolonged leaf wetness is relevant to downy mildew.
- Keep the record separate from any powdery mildew notes on the same plant.
Reading a Bremia result
Take a top result of Bremia lactucae at 35 percent. The score is above the 30 percent line, and bremia is one of the seven genera, so the app shows downy mildew steps. Two appear on this page: cutting off the spotted leaves and putting them in the bin, and watering in the morning at the base so the leaves dry quickly. The third app step refers to a product and is not repeated.
- Name returned
- Bremia lactucae
- Top score
- 35%
- Rule that matched
- genus bremia
- Downy mildew steps shown here
- 2 of 3
A name such as Peronosporaceae without a genus would still match, through the keyword fallback.
Easy errors with this group
- Calling any pale patch downy mildew without checking the underside for growth.
- Merging downy and powdery mildew notes, which the app routes to different steps.
- Watering over the foliage in the evening after reading the morning-watering step.
- Assuming a 25 percent result has the same meaning as a 35 percent one; only the second shows steps.
Limits of the label
The group label groups related organisms for general steps. It does not confirm the cause on your plant. The RHS page on downy mildews listed below describes the diseases, the EPA garden guide covers wider garden practice, and the ASPCA list answers pet-safety questions that this page does not.