Foliar Sprays of Biostimulants and PGRs Improve the Reproductive Parameters of Cacao Under Water Stress

One of the essential factors influencing yield of crops is the availability of water. This study was conducted to determine the efficacy of biostimulants (oligocarrageenan and oligochitosan) and plant growth regulators (PGRs) such as cytokinin and paclobutrazol applied as foliar spray on the pod retention and yield of six-year-old grafted ‘UF 18’ cacao trees under a monocropped system during the dry season in Type III climate of the Philippines. Tap water (control), oligocarrageenan (150 ppm), oligochitosan (150 ppm), cytokinin (40 ppm), and paclobutrazol (500 ppm) were applied as a foliar spray onto cacao trees with young cherelles (BBCH 70-72) under irrigated and rainfed conditions. Among the foliar treatments, oligochitosan caused a higher flowering intensity after four months. Paclobutrazol reduced the incidence of cherelle wilt, while cytokinin improved the pod retention of cacao. The biostimulants and PGRs generally enhanced the leaf chlorophyll content of cacao, increased the mean seed fresh weight, produced higher percentages of full beans and lesser flat beans per tree, and had a better bean count than the control. The cacao trees treated with oligocarrageenan produced pods with heavier dry beans. Moreover, heavier dry bean weight per tree were recorded from cytokinin-, PBZ-, and oligocarrageenan-treated trees. Foliar sprays of biostimulants and PGRs resulted in a significant increase in yield per tree of cacao under water stress.