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
Diane says
I have this on my plant also. First year of planting it in a pot. So beautiful but not so much now. I’m in Nebraska so I will just cut it back since cool weather is coming.
Next year hopefully I can stay on top of this issue. I’m assuming I will have to dump the dirt & start fresh, not sure if these mites live in dirt during winter months?
It was such a beautiful plant this year.
Jesse says
Hi Diane – we do not think the mites will live in the soil over winter. We recommend a few treatments with horticultural oil before you cut the plant back. Hopefully that will take care of the mites and you’ll have nice new growth when it comes back.
Amy says
Will any of the products hurt hummingbirds or bees. They all love ruella.
Jesse says
Hi Amy – none of these are harmful to hummingbirds. Spinosad is harmful to bees, but Bee Safe is not. Horticultural oil should not be harmful to bees as long as you apply in the early morning or in the evening, and do not apply while bees are actively foraging in the area.
Deanna says
I am having bad luck with my favorite plant. I planted and they looked beautiful until those white patches took over. Sprayed with a recommendation from a nursery and did nothing. Removed them since they were not looking good at all. Planted new ones in another location and it’s happening again. Bought the oil and not working. They hardly flower and look bad. Should I cut them down? Or remove them. Very upset I can’t grow these.
Wyatt says
Hi Deanna – I’m sorry to hear you are having such a hard time with your ruellia. We would still recommend cutting them back, as soon as the plants start to flush spray every two weeks with an oil for 2-4 weeks. You may also try contacting the Nueces county extension office (361-767-5223) to see if they might have any other solutions.
Jesse says
Hi Chrystyna – you can treat with spinosad year-round in hot weather, just do it in the evening when its hot out. And you can cut the plants back around January/early Feb.
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.
Jesse Jenkins says
If they look pretty bad then yes, cut them down, fertilize with Medina Growin Green, and spray with Neem OIL once they begin to resprout.
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.
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.
Rita Vidal says
Will thee mites affect all our plants? What can we do as a preventative measure to protect them?
DeAnna says
This particular mite is specific to the Ruellia. Do not worry about other plants.
Jessica Spaw says
So is it powdery mildew or mites?
Andrew F says
The mites don’t need to be treated, if its caused by mites. They are just forcing the curling of the leaf, to create a habitat that is suitable for them. It wont be affecting all the growth. They don’t harm the plant, and it will encourage other beneficial insects into your garden to allow you have an organic self contained garden without the need for insecticides. Encourage your gardens to be self sustaining. Don’t hunt down solutions to a boon you would be squandering.
Andrew F says
You can get a jewelers eye piece, and check the growth on your plant yourself. You tell us, what it is please?!
Charlotte says
These are on my hibiscus and i just replanted some larger ones next to the regrowth of smaller will the large ones also get contaminated?
DeAnna says
You probably have mealybugs which is a different bug. Spray with Spinosad soap once a week for 2-3 weeks, If you have a heavy buildup on the stems, you may want to do a light cut back of the tips and then spray.
Andrew F says
Yeah sounds like pink hibiscus mealybugs. Prolly a bit late to this reply. Getting lady bugs to get released and prevent the chemical treatment from eradicating the healthy insect is one way to treat. The other would be prune off the effected growth and bag it immediately. I find I can get control over it with bi weekly treatments of Bifen, and Imidacloprid along with some triple 20 to force green color and blooms.
Nancy B Higgs says
I live in Houston and I have been trying to find out what to do about the white splotches for months. After the freeze in February 2021, I figured that would take care of it, but no it didn’t. Recently I showed leaves to Randy Lemmon, our Houston Garden guy. At first he said it looked like I spilled paint on them, then he saw a little red mite and said to use Spinosad. Even with spraying with Captain Jack’s Deadbug which contains spinosad, the mites never seem to go away. Maybe I need to try the horticultural oil now.
DeAnna says
Yes I would try the oil spray now that temperatures are cooling down. Then cut the plants back in the Spring
Dianna Bluntzer Sherman says
Our mesquite tree leaves are covered with something that looks like this. Is it the same mite?
DeAnna says
No. You have powdery mildew. Do not worry. Let them drop their leaves for winter
Andrew F says
It also helps to have the area cleared of debris, get good air flow and remove the excess mulch and dead old growth from the base of the plant. I agree its powdery mildew. Getting to wet, plant is a jumbled mess with no active pruning causing a jumble of growth to trap moisture and produce the unsightly mildew.
Ruth Ann Moran says
Is there a home remedy