- Joanie Kift* and N J R Roets
- Agricultural Research Council - Institute for Tropical and Subtropical Crops, Private Bag X11208, Nelspruit, 1200,South Africa
- 2001
Alternate bearing is a major problem in litchi production and research aimed at stabilising production is of primary importance. One of the reasons for poor flowering is that premature development of buds in late autumn results in buds that are no longer responsive to cold-induced flower induction. This results in inconsistent flowering and yield. The manipulation of bud development during autumn to ensure bud growth during the cold winter period is therefore crucial. In this trail, the late autumn vegetative flush of ‘HLH Mauritius’ was chemically inhibited by the application of different growth inhibitors. These included Sunny®, Ethephon®, Cycocel® and a combination of Cycocel® and Ethephon®. Field observations indicated that the development of a vegetative flush could be inhibited during autumn by the application of growth inhibitors. The application of growth inhibitors resulted in a significant reduction in alternate bearing and ultimately higher and more stable yields.
Summary:
- Alternate bearing is a major challenge in litchi production, causing inconsistent flowering and yields.
- Premature bud development in late autumn prevents buds from responding properly to cold-induced flower induction, leading to poor flowering.
- Manipulating bud development during autumn to ensure growth during the cold winter is crucial to stabilize flowering.
- The study tested chemical inhibition of the late autumn vegetative flush in HLH Mauritius litchi trees using growth inhibitors: Sunny (uniconazole), Ethephon, Cycocel (CCC), and combinations.
- Ethephon acts by killing terminal buds, disrupting meristem activity, inhibiting stem elongation, and inducing leaf and fruit abscission; it can promote flowering but may cause leaf drop and reduce nutrients.
- Sunny and CCC interfere with cytokinin and gibberellin synthesis, impacting vegetative growth and flowering.
- Trials conducted in 1998, 1999, and 2000 showed growth inhibitors could reduce vegetative flush and significantly increase flowering branches.
- The combination of CCC (0.2) and Ethephon (0.1) was most effective for increasing flowering and yield, including during off years.
- Sunny also improved yield, potentially by increasing fruit size and retention rather than flowering.
- Ethephon brought about earlier flowering but not earlier fruit ripening.
- Treatments led to more stable and higher yields, reducing alternate bearing effects.
- Growth inhibitors justified the cost by yield improvements, but none are yet registered for litchi, and residue and long-term tree effects are unknown.
- Further research is needed on the long-term impact of these chemical treatments on litchi trees.