Mandevilla Vine - Knowledgebase Question

South Lyon, MI
Question by bowhead1
June 25, 2011
I have a Mandevilla Vine that was given to be as a hanging basket. I watered it and took care of it while it was in the hanging basket for a month before the weather allowed me to plant it outside in the ground and it was doing good. It's been in the ground for 3 weeks now and it has been doing fine until the past few days. It has a lot of buds getting ready to open but some of the leaves are turning yellow and have spots on them and are falling off. We've had a lot of rain and I was wondering if too much water is causing this. Can I stop the leaves from turning yellow and falling off? Is it a fungus?

Answer from NGA
June 25, 2011


Excessive rain and poorly draining soils can cause the leaves of your mandevilla to turn yellow. Typically you'll see completely yellow leaves rather than yellowing leaves with spots if your plant is reacting to being overwatered. If the spots develop after the leaves have turned yellow, it's a secondary infection. In this case, the best treatment is to pull off the affected leaves or prune your plant back to remove the damaged leaves.

If the yellowing and spotting are occurring simultaneously, I'd be more inclined to think a fungal disease has attacked your plant. You can control fungal diseases with a fungicide such as Daconil, Cleary?s, Dithane, or Kocide. Be sure to apply according to label directions. A fungicide will protect the uninfected plant parts but won't restore the affected leaves to their former green color so, depending upon the extent of the infection, you might want to prune the plant back to remove the diseased leaves, stems and flowers, and then spray with a fungicide. I know it will be hard to prune your plant back but this is the time of year that mandevillas put out tons of new growth so your pruning cuts should not be noticeable after a few weeks of healthy growth.

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