It had been many months since we last had a question at the Helpdesk concerning citrus greening (Huanglongbing Disease) in Hawaii, so when your inquiry came to the Helpdesk, we decided it was time to contact the State of Hawaii Department of Agriculture again concerning whether or not citrus greening (HLB) had been found here in Hawaii. Fortunately, although we have had the vector for spreading citrus greening (the Asian citrus Psyllid) for several years now in Hawaii, when we contacted the entomologist at the State of Hawaii DOA Plant Pest Control Division on Friday, we were happy to be told that the state of Hawaii still has found no evidence of the citrus greening disease, which is spread by the Asian Citrus Psyllid.
We are happy that you are aware of it, and a bitter taste of citrus fruit is, indeed, one of the symptoms of HLB. The fourth link below discusses additional causes of bitter or sour fruit. In our citrus orchard at the extension, we have noted that when we fail to pick all of the fruit off of a couple of the varieties of mandarin trees prior to them having a new set of blossoms, the next harvest is far more bitter than the previous. Another reason for bitter fruit is if the rootstock from which your tree had been grafted had taken over in the production of fruit on your tree. This will always result in bitter or sour fruit that is inedible.
In this day and age, the spread of Huanglongbing worldwide seems inevitable, so we are hoping that you will continue to be on the lookout for it. HLB has already had a devastating impact on Florida’s citrus industry, and we certainly do not want it to impact any of our citrus growers, if at all possible. Although HLB is caused by a bacteria spread by the Asian Citrus Psyllid, there is no known treatment.
We have included links to five informative articles concerning citrus greening, the Asian citrus Psyllid, and the causes of bitter fruit.
Thank you for being aware of this problem, and please continue to be vigilant.