5 Causes of Mandevilla Leaves Turning Brown[Solution & Prevention]

The Mandevilla vines are an outstanding addition to any landscape. These vines are so versatile that they can be grown in the pots, or along a wall or it can be twined up a trellis. The stunning trumpet-shaped flowers with glossy leaves are a treat to watch.

But sometimes Mandevilla leaves can start turning brown and fall off. This means you need to take some quick actions before it’s too late.

So if you are wondering why the Mandevilla leaves are turning brown and falling off, then let me explain.

There are several causes of Mandevillas brown leaves including Fungal Diseases, Bacterial wilt, Inconsistent Watering, and Environmental Stress.

As you go through this article, you’ll find the possible causes along with their solutions to your brown leaf problems.

So Let’s get down to business-

  Why Are Mandevillas Leaves Turning Brown?

1.Fungal Diseases of Mandevilla

Fungal attacks are a very common problem in Mandevillas. Fungal leaf spots, Botrytis blight, Sooty mold, and stem rot are the main fungal diseases for Mandevilla.

Several fungi can cause fungal leaf spots. The disease appears to be brown spots on the leaves. Severe infection can make the leaves curl and fall off.

Botrytis blight is another fungal problem of Mandeville. It is most problematic for the cool regions, especially where the temperature goes under 15 C. 

The infected Mandevillas develop yellow leaves that later turn brown and wilt. Even the buds and flowers get covered by a gray growth of mold.

Sooty mold makes a brown and black coating on your Mandevilla’s leaves. Sometimes the molds cover the branches too.

But it isn’t a typical plant fungus. It grows on the honeydew. And you probably know that aphids are the ones that secret honeydew. So getting rid of aphids is a must.

The stem rot makes the Mandevilla vines yellow and then brown. The entire twigs and branches wilt. If you don’t take immediate action the plant can even die.

Control Measure

Firstly, remove the infected leaves carefully and dispose of them away from your garden. Then you need to apply a fungicide.

But here is the thing, there are many kinds of fungicides available in the market. All are not suitable for Mandevilla. You need to apply a fungicide that is best for your flowering Mandevilla plants. (our pick: Bonide Copper Fungicide)

To control sooty mold you need to kill the aphids with a good insecticide that is designed for flowering plants (our pick: Garden Safe Brand Ready-to-Use Garden Insect Killer)

Here I am adding some home remedies that are useful and easy to make. For any kind of fungal problems you can try these recipes below:

#Recipe 1:-Cinnamon Spray Recipe

Ingredients:

  • 4 Tablespoons of Cinnamon
  • 2 Liters of water

Steps:

  • Add water and cinnamon together and shake very well 
  • Let it sit for a few hours
  • Strain the mixture with a fine cloth
  • Put the mixture into a spray bottle
  • Spray it in the stem and leaves of the infected plant until the problem solves.

#Recipe 2:-Baking Soda Spray Recipe

Ingredients:

  • 1 teaspoon of baking soda
  • 1 teaspoon of dishwashing liquid
  • 1/2 teaspoon of any cooking oil 
  • 1 liter of water

Steps:

  • Mix all the ingredients very well. 
  • Then pour it into the sprayer.
  • Spray on both sides of the infected leaves up to twice a week.

Note: Always try a small part of the homemade recipes into a small area of the leaf. If you see leaf damage then make it into a milder solution by adding water. Or you can stop applying that recipe and try a different one for your Mandevillas.

Preventive Measure

If you suspect a fungal attack on your potted Mandevillas then you can consider repotting them in fresh soil. 

Always disinfect garden tools and equipment with any disinfectant or bleach.

Dense planting lowers the air circulation and encourages fungal growth so keep proper planting space.

Avoid sprinkling water on the leaves. Water in the morning so that any wet leaves can dry out in the sun.

2.Bacterial Wilt Of Mandevilla

Bacterial wilt is a devastating disease of a wide range of ornamental plants including Mandevilla. This disease occurs in high temperatures usually over 85°F.

The bacterias block the vascular tissues. Therefore, enough water and nutrients cannot reach the stems and leaves.

As a result, the Mandeville starts to wilt and the leaves start to turn yellow and then brown. Eventually, the leaves start falling off and the plant dies.

Control Measure

Bacterial wilt is hard to get rid of. You need to apply a specialized copper fungicide(our pick: Bonide Copper Fungicide). You can also disinfect the soil and containers with chemical disinfectants

You can also try this homemade copper spray with some caution as the chemicals are corrosive.

#Recipe 1:- Copper Spray Recipe

Ingredients:

  • half a gallon of water
  • 25 ml of copper sulfate
  • 5 tablespoons of hydrated lime

Steps:

  • Mix water and hydrated lime first in a plastic container. Do not use a metal container as the ingredients can react with metal.
  • Keep stirring the mixture with a plastic spoon
  • While stirring add the copper sulfate into the container.
  • Shake the mixture thoroughly before spraying. This mixture settles down easily so while spraying keep shaking it once in a while
  • After spraying, wash the sprayer very well because this mixture is corrosive.
  • Do not store it. Use a freshly prepared mixture.

3.Inconsistent Watering

Water availability plays a big role in the browning of Mandevilla leaves. Mandevilla is a tropical plant so it prefers moist and nutrient-rich soil for blooming.

Underwatering along with any nutrient deficiency is more likely to turn the leaves brown. Eventually, the leaves can even fall off. 

Check the soil moisture with a good moisture meter to avoid underwatering problems(Our pick: Atree Soil Soil Tester Kits with Moisture, Light, and PH Test for Garden)

Control Measure

Pick out the brown leaves so that the plant can grow some more new leaves instead.

Check your Mandevillas soil especially in hot and dry conditions. Water up to twice a day if the temperature reaches over 85 °F. 

Potted Mandevilles dry out quickly so keep an eye on their moisture conditions frequently. Make sure there are enough drainage holes in the pot.  

Nutrient imbalance can also cause stress to the plant. So a good dose of water-soluble fertilizer for blooming Mandevilles once a month can also be very effective against the browning of leaves (Our Pick: Miracle-Gro Water Soluble Bloom Booster Flower Food)

4.Environmental Stress

Generally, Mandevilles are very stress-tolerant plants. Still, they do have a limit. They need 6 to 7 hours of direct sunlight every day. 

But if the weather is too hot and there’s too much sun exposure then some of the leaves can get burned. As a result, the edges can start to become brown. 

Mandevilla cannot tolerate low temperatures at all. When the temperature falls to 45 ° F or 10 °C the buds start to turn brown and the plant starts to die. 

There is one more thing that can stress the plant and result in brown leaves. It’s the over-application of fertilizers. 

This occurs more in potted plants as they have limited soil in the pot. An overdose of fertilizer accumulates more salt in the soil that sometimes injures the plant. 

Control Measure

Trim the brown parts of your Mandevilla leaves with a pair of scissors. 

If you think you’ve added too much fertilizer on your potted Mandevilla then consider repotting it in fresh soil. 

In case of too much heat, move the potted Mandevillas to shade in the afternoon. 

Keep your Mandevillas outdoors in the summer and then bring them indoors in the winter. Do not fertilize during the winter as they stay dormant in this period.

Conclusion

Don’t wait up. If you see the Mandevilla leaves turning brown, find out the exact problem with the help of this article and start taking necessary actions. 

Apply fungicides, insecticides and try the homemade recipes to revive your plants.

I have tried to talk about all the things that can turn the Mandevilla leaves brown. I hope you found this article helpful.

Share your experience or any problems related to the browning of Mandevilla leaves in the comments below. 

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