Effect of full-cover ethephon applications on flowering and yield of 'Mauritius' litchi in South Africa
Currently, ethephon is used by South African growers as spot spray to control autumn/winter flush, but such applications generally have to be repeated several times due to re-occurring flush. In order to reduce the amount of applications, trials were conducted to determine whether a once-off full-cover ethephon application after the last post-harvest flush (at dormant stage) could inhibit new leaf flush long enough until temperatures become conducive for flower induction in order to increase flowering and yield. A trial was conducted in Nelspruit, South Africa, on 'Mauritius' ('Tai So') litchi trees during the 2014 and 2015 litchi seasons. Ethephon (a.i. 48%) was applied as a once-off full-cover spray after hardening of the last desired post-harvest flush at the concentrations of 0, 500 and 1000 ppm at the end of March, mid and end of April. The control trees were treated with spot sprays as per current farm practice (at 1000 ppm whenever young shoots appeared). Shoot control on the control trees started at the end of March and needed to be repeated twice. Tree response was monitored at regular intervals after spray applications. Shoot growth, days to flower panicle emergence, flowering and yield was recorded. In both years, concentration and timing of full-cover ethephon applications affected the growth of leaf flush and time of flower panicle emergence. As a result there was no or little vegetative growth during the flower induction period (April/May) as well as later flower panicle emergence. The higher the applied concentration was, the later was flower panicle emergence. Overall, applications up to mid-April increased flowering and yield. Application after mid-April delayed flower panicle emergence too long, leading to reduced flowering and yield, and increased winter/spring flush. It could be shown that one timely full-cover ethephon spray can substitute the frequent spot sprays that are currently used in the South African litchi industry.
Cronje, R.B. and Ratlapane, I.M. (2018). Effect of full-cover ethephon applications on flowering and yield of 'Mauritius' litchi in South Africa. Acta Hortic. 1211, 71-78
shoot control, ethephon, dormancy, flower induction, flower panicle emergence