Pg. 63-71 The use of plant growth substances to reduce fruit drop and increase fruit size in litchi

Application of plant growth substances on litchi fruit resulted in improved fruit retention and fruit size. Trials were undertaken in the Malelane and Nelspruit areas to determine the effect of synthetic auxins and cytokinins on fruit set and retention of ‘HLH Mauritius’. In Malelane, the synthetic auxins Corasil E® (Dichlorprop) at a concentration of 100 and 125 ppm and Maxim® (TPAJ at 50 ppm were applied when fruit weighed approximately 2 g. Applications were done on trees and branches, but on branches 75 and 150 ppm Corasil E® treatments, as well as 0.4% Kelpak® were also included. With the branch treatments fruit retention was significantly improved by the 100 and 125 ppm Corasil E® and 50 ppm Maxim® treatments. The 125 ppm Corasil E® treatment, however, gave significant smaller fruit. The other treatments had no significant effect on fruit size. However, on the full tree applications none of the treatments had any significant effect on fruit retention, fruit size and production. In the Nelspruit trial the synthetic cytokinin, CPPU, at a concentration of 20 ppm was applied two and three weeks after full female bloom. In another treatment a 5 ppm NAA application two weeks after full female bloom, were followed by a 20 ppm CPPU application three weeks after full female bloom. Fruit retention was slightly, but not significantly, lower in all the treatments. Fruit size was improved in all treatments although only the 20 ppm CPPU treatment three weeks after full female bloom gave significant larger fruit.

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