Effect of Paclobutrazol Application on the Phenological Patterns of Flowering, Fruit Production and Cherelle Wilt Incidence in Cacao (Theobroma cacao L.)

Cherelle wilting, a major constraint in cacao production, is caused by inefficient carbohydrate distribution in developing cherelles. Understanding carbohydrate metabolism in cacao can improve our knowledge of its physiology and help develop yield-enhancing strategies. Improving carbohydrate assimilation in cacao during critical flowering and pod setting stages requires thorough analysis of physiological, biochemical, and molecular processes, necessitating prompt intervention. Paclobutrazol (PBZ) by inhibiting gibberellin biosynthesis, can increase carbohydrate accumulation in sink tissues. This boosts photoassimilate partitioning to the reproductive structures, sustaining cherelle growth and improving cacao yield. In a separate study, two cacao varieties (UF667 and UF18) were applied with paclobutrazol to enhance flower, cherelle, and pod production. Ten-year-old trees were treated with 0.1% paclobutrazol, untreated trees served as controls. Vegetative growth, flower, cherelle, and pod production were recorded monthly. Carbohydrate content and leaf SPAD values were determined in UF667 leaves. Data were analyzed using Pearson Correlation and T-test at a 95% confidence interval. Paclobutrazol enhanced chlorophyll (as represented by leaf SPAD value) but did not significantly affect carbohydrate accumulation in cacao leaves. Increased leaf SPAD value in mature leaves boosted flowering intensity and cherelle formation. PBZ increased the total number of flower cushions and flowers per tree in UF18, and the total flowers and flowers per cushion in UF667. Cherelle formation and pod retention in PBZ-treated trees were not significantly different from untreated trees. Flower production increased by over 100%, but the conversion rate to cherelles and pods was very low. Paclobutrazol increased dried bean yield from 1.18 to 2.84 kg per tree per year in cacao var UF18, much higher than the local production. Cherelle wilt increased with more cherelles and pods, indicating competition for photoassimilates. Overall, PBZ was effective in enhancing flower production in cacao. However, proper cultural management practices, such as pruning and pest control measures, should be implemented alongside paclobutrazol to sustain the growth of developing cherelles and improve pod retention.