Role of Fungal Pathogen in Citrus Fruit Drop at Center of Symposium

In September 2021, KeyPlex, a plant health product supplier, invited me to attend a peptide symposium. The use of peptides in citrus has become a hot topic in the past year, so the event drew about 80 growers and other industry stakeholders. KeyPlex presented the learning session at Streamsong Golf Resort in Bowling Green, FL. The company says it chose to host the event because of the interest and the fact all of their products are based on peptide technology. Gerald O’Connor, President of KeyPlex, welcomed the group and noted the interest. “We’ve talked to many growers and understand their interest but also saw there were a lot of questions about peptides,” he said. “We felt it was important to host this event to provide answers to those questions. And it is important to us to hear from the growers about solutions they are seeking to improve production in their groves.” One of the products featured at the symposium was KeyPlex’s new product, KP-120, a peptide-based technology. The micronutrient product promotes root growth and also has fungicidal activity. According to Mauricio Flores, the fungicidal activity is an important distinction. Flores consults with KeyPlex on product development and evaluation.

Fungal Discovery

In June 2021, Flores pulled more than 200 leaf, fruit, and twig samples across Central Florida and made a surprising discovery. The samples showed large populations of the fungus Glomerella cingulate, which is the sexual stage of the Colletotrichum gloesporoides fungi. What makes the discovery potentially noteworthy is an observation Flores made on a coffee plantation in Costa Rica where early and late fruit drop and twig dieback arose as a significant problem in only two seasons. By the second season, fruit drop had grown to 60% on the coffee plants. Flores isolated the G. cingulate fungus in samples collected on the coffee pants. Flores developed a fungicide program that included KP-120 aimed at controlling the fungus. Fruit drop and twig dieback were reduced dramatically. KP-120’s peptide and systemic activity, along with a fungicide, provides synergistic control of the fungus. For citrus growers plagued with fruit drop and twig dieback in their groves, this could be a very meaningful discovery. If similar results occur in citrus as did in coffee, it could be a long-sought solution to fruit drop.

Evaluating Tactics

Currently, the company is cooperating with growers to determine the best application timing, methods, and rates. Eight to 16 fluid ounces of KP-120 applied 60 to 30 days pre-harvest, along with a fungicide, is the current standard recommendation. But as Flores noted, those recommendations will evolve as more is learned. O’Connor told me KeyPlex was excited to bring the discovery of G. cingulate and its potential role in fruit drop to growers. He says plans are underway to reconvene with growers in February to discuss how various timing and rates of application impacted fruit retention and yields.