How to make pumelo (oriental grape fruit) to get sweet.

Would you please help to tell me what to do in order to make my pumelo to get sweet. My pumelos start to bear fruit about 5 years. The very first year. It was very sweet and then, last year plus 3, 4 years before that,. it was not . Secondly, what you recommend to spray to kill the fungus and foliage problem.
Thank you very much
Tai Nguyen
  7 answers
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