Fruit Drop in Citrus

Fruit drop is a natural, physiological phenomenon that occurs in all citrus varieties. However, pre-harvest fruit drop often causes distress and concern as it can result in significant yield reduction as well as loss of tree resources in a non-harvested fruit.For citrus trees grown in Florida, increased drop of mature fruit prior to harvest is one of the many symptoms of Huanglongbing (HLB) disease, caused by Candidatus Liberibacter asiaticus (CLas). This HLB-associated pre-harvest fruit drop, in addition to tree decline, results in a concomitant reduction in fruit production. For example, for the late-season ‘Valencia’ sweet orange, the rate of pre-harvest fruit drop was 14% for the 2009-2010 production season, whereas the rate rose to 30% during the 2016-2017 season. To date, how HLB escalates pre-harvest drop in citrus remains unclear.