The leaf spots on the Bauhinia kockiana vine are black and hence I call it black leaf spot. Fungi may appear as black dots in the spots, either in rings or in a central cluster. Over time, the spots may combine or enlarge to form blotches.
Notice that the leaf spots grow and oftentimes would have yellow rings or halos. These are the symptoms of the Black Spot fungi in roses.
Life Cycle of the Leaf Spot Fungus
The organisms that cause leaf spots survive in fallen infected leaves and twigs. Some may remain in dead twigs on the tree. During the rainy season, spores may splash or be windblown onto newly emerging tender leaves where they germinate in the moisture and infect the leaf. Overhead watering can also provide prolonged wet periods that are ideal for spreading leaf spot diseases.
Even if the infected parts of the leaves are cut, the leaf spots continue to spread if left untreated. Shown below are leaves that were cut to remove the leaf spots. The spread of the leaf spot fungi did not stop.
The young leaf buds that are just sprouting would not have the symptoms indicative of leaf spot. So it is important to start treating the plant with a fungicide that will protect the young leaf buds as soon as possible. Here are the leaf buds that appeared just before I started the leaf spot treatment.
Steps to Treat the Black Leaf Spot on Bauhinia Kockiana
- Remove the parts of the leaves that are heavily infected with the black leaf spots. Use a pair of pruning shears to do this. Collect all cut pieces in a bin. Throw all these in the trash or burn them.
- Dispose all rubbish on the ground where the Bauhinia kockiana are planted. This would include the cut infected parts that may have dropped.
Shown below are two plants, one on the left and another on the right. In my case, there were some strange looking grayish-brown mushrooms growing at the base of one plant. I removed those too.
- Spray all foliage with a broad spectrum fungicide. I used Dithane M-45. Its active ingredient is mancozeb. Follow the instructions on the package for proper application. Since I use just a little amount of this powder, I scoop it with a homemade dispensing spoon into a spray bottle or a conventional garden sprayer.
- For the first treatment, apply fungicide to the ground as well. If there is little fungicide left in your spray bottle, pour the remaining contents on the base of the plant.
- After treating the soil, apply new mulch to the ground at the base of the infected plant. Here, I used charred rice hull as mulching material.
- Spray the fungicide in the morning when the leaves have dried from the morning dew. Depending on the infection, spray twice-a-week at the most and once-a-week at the least. Because of the severe infection on the Bauhinia kockiana, I sprayed twice a week for one month.
- Be vigilant of rains. If there is a strong downpour after spraying, you may re-apply the fungicide. This is to ensure adequate coverage on foliage that may have lost the fungicide due to the rain.
Results of the Fungicide Treatment on the Black Leaf Spot
After three weeks of twice-a-week fungicide application on the Bauhinia kockiana plants, here are the results.
The new leaves that have sprouted from the leaf buds (in the third photo of this page) now seem clear of the the leaf spots.
Here's another branch of the Bauhinia kockiana vine. The leaves here also are clear of the black spots.
The other plant, however, still shows some black spot infestation as shown in the photo below.
Therefore, it would be more prudent to continue the fungicide application for both plants until the black leaf spot is totally eradicated.
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