I am having trouble with this. The spray mix I got from the plant store is only marginally reducing the growth. Can anyone suggest a good treatment for this? Thanks.

Hard to see detail in the photo. Are you sure its a fungus? Or maybe a mealy bug infestation. It doesn't appear to be powdery mildew or white fly.

 

In either case:

If the one small plant shown is all you have, then just wipe off the white material with a soft cloth, damp paper towel or a cotton gloved hand. Monitor weekly and repeat mechanical control.

Neem seed oil spray mixed according to label and apply with a hand-held pump up sprayer or an ironing type hand pump spray bottle. Apply weekly until infection or infestation is no longer present, then go to every two weeks or at least once a month for prevention.

An alternative, especially if a minor leaf fungus, is to spray with a baking soda solution (sodium bicarbonate) . I'm not sure if Green Cure or Kaligreen fungicides are available in Thailand, but if you look at these product labels available on the Internet you may find a Thai brand with similar ingredients and percent active ingredient. And you can look at the product labels for mixing and application guidelines.

 

Improve growing conditions as best possible with appropriate water and fertilizing. Provide and maintain soil organic matter content with compost mulch. Avoid overhead watering, which may contribute to fungal growth. To go the full route for important plantings, soil testing and prescription amendments are key.  Plants with good growing conditions and mineral balanced soil with good soil biology activity will resist pests and disease.

product04-bicarbonate.pdf

GreenCure_Label_2015.pdf

Edited December 21, 20169 yr by drtreelove
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Also, pick off the older infected leaves regularly,. It appears to be heaviest on the older leaves in senescence, and spreading from there to green leaves.