The past couple weeks, several customers have brought in pieces of Ruellia (Mexican Petunia) with worrisome white splotches on the leaves. At first glance, it could appear to be a fungal issue or even a chemical or paint residue, but that’s not it… Here’s what to look for and our recommendation for treatment.
The white funk is actually a type of growth distortion called erineum caused by tiny mites called eriophyid mites (Acalitus ruelliae). So that means fungicides would be a waste of time and money to solve this issue. We recommend treating organically with All-Seasons Oil Spray (a horticultural oil). Repeat the treatment every 5 to 7 days for a total of 3 treatments, wait until Spring, then cut the plants down to ground level. This should kill the mites and the plants should grow back out and look beautiful again. Another approach would be to use organic Spinosad soap or Bee Safe 3-in-1 Spray to treat the mites, then cut to ground level in Spring and wait for clean regrowth.
-DeAnna
Kimberly A. Griffith says
Hi, I have many of these Ruellia throughout my garden for 20 years. I live in Florida and every year I cut them back. This is the first year this white powder has shown itself sadly and it has started to spread quickly throughout my garden. I cut them all back in February & March when weather started to warm up. It’s now April 90 degree weather and the white powder is overtaking these flowers. All my other blooming plants are mixed together with my boxwoods, pentas, inpatients, crotons, palms, blue daze, and I am in fear it will spread to them. What is the best way to treat them without harming the other plants & flowers?
DeAnna says
Ruellia mites only affect Ruellia. You can cut them down, fertilize, and then spray with Neem oil to suffocate the mite. The other pants will be fine.