Saving Citrus Symposium Focused on Fruit Drop

KeyPlex recently hosted its third Saving Citrus Symposium in Sebring, Florida. The event focuses on fruit drop, which has been a major problem for growers in recent years.

The third gathering provided an update on research KeyPlex has sponsored to seek causes of fruit drop and ways to manage against it. The research began in January 2021 when company personnel began collecting samples from citrus groves.

These samples identified the presence of the pathogen Colletotrichum gloeosporioides on the calyx, peduncle, twigs and fruit. This is the sexual stage of Glomerella cingulata. The pathogen was found in the calyxes at all locations where the samples were pulled. The pathogen attacks the peduncle and calyx zone where fruit is set.

According to Gerald O’Connor, chief executive officer of KeyPlex, these findings led to the hypothesis that the pathogen was having a causal effect in fruit drop. As the company searched for more information, it found Vladimiro Guarnaccia, associate professor of plant pathology at the University of Torino in Italy, who had been studying the pathogen for some time.

KeyPlex sponsored research by Guarnaccia to study the phenomenon in Florida. He presented the results of this research during the symposium. That research has also turned up evidence that C. gloeosporioides has developed resistance to current fungicides used in citrus.

Prior knowledge regarding C. gloeosporioides had identified the pathogen as a post-harvest problem on fruit, which it can be. But Guarnaccia’s research suggests it is a preharvest pathogen as well, causing fruit drop in Florida citrus.

Guarnaccia has authored a research paper on the pathogen’s role in twig dieback and stem end rot. A second research paper on C. gloeosporioides is soon to be published.

KeyPlex is developing a management program that includes the use of its KP 120 product and essential-oil based biopesticides like AWP and Sporan. O’Connor called on the Florida-based research community to study C. gloeosporioides more because the company’s research suggests it plays a significant role in fruit drop.

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