OPTIMIZATION OF GROWTH RETARDANTS FOR CANOPY MANAGEMENT IN GUAVA (PSIDIUM GUAJAVA L.) CV. LUCKNOW-49 UNDER ULTRA-HIGH-DENSITY PLANTING

Abstract

The present investigation was undertaken to optimize the application of growth retardants for canopy management in guava (Psidium guajava L.) cv. Lucknow-49 under ultra-high-density planting conditions. The study was conducted from June 2025 to April 2026 at the college orchard of SRM College of Agricultural Sciences, Chengalpattu, Tamil Nadu, India, using four-year-old trees planted at a spacing of 4 × 2 m. The experiment comprised seven treatments involving three levels of paclobutrazol (2.5, 5.0 and 7.5 ml tree⁻¹) combined with two concentrations of ethephon (400 and 600 ppm), along with an untreated control, and was laid out in a Randomized Block Design with three replications. Growth and canopy parameters, including plant height, shoot length, leaf area index (LAI), and east–west and north–south canopy spread, were recorded. The application of paclobutrazol and ethephon significantly restricted vegetative growth compared with the untreated control. Plant height and shoot length were maximum in the control (3.11 m and 35.00 cm, respectively) and minimum under T6, comprising paclobutrazol 7.5 ml tree⁻¹ + ethephon 600 ppm (2.30 m and 26.66 cm, respectively). Canopy spread was also greatest in the control, measuring 4.08 m in the east–west direction and 3.96 m in the north–south direction, while the minimum spread was recorded under T6 (3.20 and 3.08 m, respectively). In contrast, LAI increased with the application of the growth retardants and reached its maximum under T4 (paclobutrazol 5.0 ml tree⁻¹ + ethephon 600 ppm) at 2.91, followed by a decline at the higher paclobutrazol dose. Overall, the results demonstrated that combined application of paclobutrazol and ethephon effectively regulated vegetative and canopy growth in guava under ultra-high density planting, with T6 producing the strongest canopy restriction and T4 providing comparatively favourable leaf area development.