Help me take care of this diseased plant?

February 28, 2016 1:29 PM

I'm not sure what type of plant it is, but it has some sort of mildew killing it.

I took in this abandoned plant. I'm not sure what it is, but it seems to be sick.

It has large leaves that are mostly a rusty color fading to a yellow-green around the edges. The leaves come off of thick green branches. From googling, I thought it might be a type of rhizomatous begonia, but I'm not sure. There is a whitish mildew looking stuff on its branches, and the leaves are dying, turning papery and dry with spots of mildew. The healthier leaves have an almost rubbery, skin-like, plump feeling to them.

Here's a picture of its leaves. Here's a diseased leaf, and here's the mildew stuff on the branches.

Any ideas what this plant it, or how to kill this mildew? Thank you!

posted by ohsnapdragon to Home & Garden (5 answers total)

It's a begonia that looks like it's hosting some mealy bugs. They tend to leave white fluff on stems. They sometimes hang out at the edge of the soil line. A coating with insecticidal soap should help.
posted by batbat at 1:34 PM on February 28, 2016 [1 favorite]

Best answer: I agree with batbat that they're mealybugs, but soap won't penetrate the waxy coating of the bugs. Get some systemic insecticide, which will be taken up by the plant, spread through its system and poison the bugs when they drink its sap. Normal spray on stuff won't work. The stuff you want comes in several forms, but you might find it easiest to get a set of "pins" that you push into the compost that release the insecticide when the plant is watered.
posted by Solomon at 1:50 PM on February 28, 2016

Best answer: Your plant is a Begonia corallina, and I disagree with the above diagnoses - I don't think that's mealybugs, I think it's a fungal infection called powdery mildew.

Here is a google image search of begonias with powdery mildew and here are some resources (1, 2, 3) that suggest fungicides.
posted by vegartanipla at 2:45 PM on February 28, 2016 [2 favorites]

I'm not convinced those are mealies but if they are you should do two things - use a fine paint brush and some rubbing alcohol on all the stuff you can see. Just a swipe is enough to kill them. Then quickly wash all the alcohol off under the tap. It works best if you use a magnifying lens as well as some of the bugs are tiny are hard to see. Be sure and check under the leaves and around the edges and bottom of the pot as well. Repeat weekly for about 3 weeks to ensure you have caught as many as you can - there reproductive life cycle is 1-2 weeks. Then get a systemic that won't kill your particularly plant. Be careful some systemics are awful for some plants.
posted by srboisvert at 4:22 PM on February 28, 2016

Another vote for mildew, not mealybugs.

I've had an ongoing issue with a different fungus on some of my plants and found that sulfur sprays (recommended in one of vegartanipla's links as well) worked better than the other options I tried (hydrogen peroxide, baking soda, chlorothalonil). No guarantees, since both your plant and your fungus are different, but sulfur would still be my recommendation.
posted by Spathe Cadet at 11:05 AM on February 29, 2016