Pg. 17-20 Preliminary Results of the Effect of Plant Growth Substances on Litchi Fruit Size and Retention

Synthetic auxins are known to affect fruit drop and size, depending on the application time and concentration used. A trial was thus undertaken to evaluate the effect of different synthetic auxins and girdling on fruit size and retention of ‘HLH Mauritius’. In this cultivar a second wave of fruit drop took place 7 to 9 weeks after full female bloom
(FFB). Control trees in the Malelane area abscised 41.04% of the fruit that survived the initial fruit drop period while 24 % were abscised in the Nelspruit area. In the Male lane trial this fruit drop was reduced significantly by the 100 ppm TP, 100 ppm TP plus 20 ppm TPA and 67 ppm TP plus 20 ppm TPA treatments. These treatments had 9.86, 12.10 and 12.92 % fruit drop respectively and the reduced fruit drop resulted in higher yields of 130, 121. 7 and 117 kg/tree respectively in comparison to the 97.3 kg/tree of the control. The 100 ppm TP and the 100 ppm TP plus 20 ppm TPA treatments also had bigger fruit than the control. In the Nelspruit trial the 100 ppm TP plus 20 ppm TPA and the 67 ppm TP plus 20 ppm TPA treatments reduced fruit drop and the biggest fruit were obtained by the 100 ppm TP plus 20 ppm TPA and the SO ppm Quinmerac treatments. Both of these treatments produced average fruit of 20.S g in comparison to the 19 g of the control.