Help! What are These White Splotches on My Ruellia?

gillnurseryProblem Solving26 Comments

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

26 Comments on “Help! What are These White Splotches on My Ruellia?”

  1. Our mesquite tree leaves are covered with something that looks like this. Is it the same mite?

  2. 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.

    1. Yes I would try the oil spray now that temperatures are cooling down. Then cut the plants back in the Spring

  3. 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?

    1. 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.

  4. Will thee mites affect all our plants? What can we do as a preventative measure to protect them?

    1. 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.

  5. 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.

  6. 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.

  7. 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.

    1. 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.

    1. 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.

  8. 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.

    1. 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.

    1. Yes – neem oil or Spinosad soap if you want to cut back and treat this Fall. Or wait until January and use All Seasons Horticultural Oil which is heavier and should be used when temps are cooler.

    1. Hi Joey. We doubt that regular dish soap would be effective. Horticultural oil is effective because it’s heavy and suffocates the mites. Spinosad soap contains Potassium Salts of Fatty Acid (18.8%) and Spinosad (0.1%) which act to kill the mites.

  9. Thank you! im in florida, looks like i have this exact issue. i have the spray ordered and will follow recommendation! since our “winter” is pretty moderate to say the least, would you still recommend cutting to ground in spring? our ruellia have only been planted 2-3 months

  10. You should definitely cut your plants back, the last week of January or first week of February. If they are still rather small, 12 inches or less, just prune off 2 to 4 inches, but if they are 2 feet or more, cut them back by at least half, cut as much as down to just 4 inches tall.

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