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
Sally says
Is it too hot on June 22, 2022 to use horticultural oil?
Jesse says
Hi Sally – yes it is too hot to use horticultural oil this time of year. If you choose to use Spinosad or Bee Safe, make sure the plants are well hydrated, and spray in the evening when its cooler.
Dean says
I have this white fuzz/ mites on my Ruella plants. I see about using the All Seasons Horticulture spay oil, but I have an unopened bottle of Neem oil…can I use that instead. It’s early April, so I dont know if I should treat and cut plants to the ground at this point.
Chrystyna Kosarchyn says
I live in the Florida Keys and my Ruellia does not get cut down for the winter so how to deal with these mites? Is there anything I can spray that would be ok for our year-round hot weather? Should I cut it back even if there is no winter here? And, if so, when? I do cut it back every so often, otherwise they grow too tall and leggy.