Influence of Prebloom Foliar Application of Plant Growth Regulators on Reproductive Performance and Nut Set in Cashew (Anacardium occidentale L.)

Cashew (Anacardium occidentale L.) is a commercially important crop, but poor fruit set and low fruit retention limit productivity, with only 1–2% of flowers maturing into fruits. To address this yield constraint, the foliar application of exogenous plant growth regulators has emerged as a potential strategy because it can influence key physiological processes such as flowering, fruit set, and retention. The study was conducted during 2024–2025 at the Cashew Research Station, Madakkathara, using the cashew variety Sulabha. The study evaluated eight foliar spray treatments: salicylic acid (SA) at 1000 ppm and 2000 ppm, gibberellic acid (GA₃) at 75 ppm and 100 ppm, naphthalene acetic acid (NAA) at 75 ppm and 100 ppm, water spray, and an absolute control. Prebloom foliar application of growth regulators significantly influenced flowering laterals, inflorescences and nut numbers per square metre, whereas non-flowering laterals, male and hermaphrodite flower counts and sex ratio were not significantly affected. GA₃ 75 ppm and NAA 75 ppm recorded the highest number of flowering laterals (13.25 m⁻² and 12.92 m⁻², respectively). NAA 75 ppm and GA₃ 75 ppm recorded the highest numbers of inflorescences (19.08 m⁻² and 18.83 m⁻², respectively). NAA 75 ppm recorded the highest number of nuts per m² (32.17 m⁻²), which was statistically on par with GA₃ 75 ppm (28.50 m⁻²). The higher nut set under NAA 75 ppm and GA₃ 75 ppm was mainly associated with greater numbers of flowering laterals and inflorescences, which may be attributed to improved floral differentiation and assimilate partitioning. Overall, prebloom foliar applications of NAA at 75 ppm and GA₃ at 75 ppm may improve flowering and nut set in cashew in the central plains of Kerala. Further evaluation across seasons, varieties, and locations is required to validate their wider applicability.