Pg. 5-7 The Correct Use of Growth Inhibitors Can Become Part of a General Orchard Management Programme

The effect of autumn application of different growth inhibitors on ‘HLH Mauritius’ and ‘McLean’s Red’ production has been investigated during the past four years. The correct use of growth inhibitors resulted in a significant reduction in alternate bearing and ultimately higher and more stable yields. Ethephon^® and CeCeCe^® in combination, or Ethephon^® on its own, are the preferred growth inhibitors to be used. In ‘McLean’s Red’ the production of control trees was 19 kg per tree while CeCeCe^® in combination with Ethephon^®, and Ethephon^® on its own gave productions of 24.3 and 26.9 kg per tree respectively. The use of growth inhibitors also improves fruit size in ‘McLean’s Red’. The best results for ‘HLH Mauritius’ were obtained during an ‘off year’ when the production of control trees was 24.48 kg per tree while CeCeCe^® in combination with Ethephon^®, Ethephon^® on its own, and Sunny^® gave productions of 44.95, 34.46 and 35.98 kg per tree respectively.

Abbreviations: CeCeCe^®, Cycocel, chlormequat chloride; Sunny^®, uniconazole.

Summary:

• The study investigated the effect of autumn application of different growth inhibitors on the production of HLH Mauritius and McLeans Red litchi over four years.
• Correct use of growth inhibitors significantly reduces alternate bearing and results in higher, more stable yields.
• Preferred growth inhibitors are Ethephon alone or in combination with CeCeCe (Cycocel).
• In McLeans Red, control trees produced 19 kg per tree, while CeCeCe plus Ethephon and Ethephon alone yielded 24.3 kg and 26.9 kg per tree respectively.
• Growth inhibitors also improved fruit size in McLeans Red, with treated trees producing a larger proportion of fruit in the export-size category.
• In an off-year for HLH Mauritius, control trees yielded 24.48 kg per tree, while combinations of CeCeCe plus Ethephon, Ethephon alone, and Sunny yielded 44.95, 34.46, and 35.98 kg per tree respectively.
• Growth inhibitors act by causing abscission of young leaflets and inhibiting growth of new shoot flushes, which thereafter promote flower initiation when temperatures drop.
• Timing of application is critical, and the inhibitors should be applied to young, actively extending vegetative flushes.
• Sunny, though effective, is more expensive and less effective if applied late in the season.
• The recommended treatment is 2000 ppm CeCeCe combined with 500-1000 ppm Ethephon.
• Growth inhibitors are valuable for increasing yield, fruit size, and managing flowering cycles but are not yet registered for litchi use.
• The study highlights the importance of integrating growth inhibitors into orchard management to improve production consistency and quality.