Effect of paclobutrazol on growth and flowering of lychee (Litchi chinensis)

Abstract

The effects of either foliar (1.00-4.00 g/L) or soil applications (0.25-1.00 g/m2 tree ground cover) of paclobutrazol, during autumn, on vegetative flushing and flowering of 3 lychee (Litchi chiriensis) cultivars (Bengal, Kwai May Pink and Tai So) were investigated over 3 years at 8 sites in subtropical southern Queensland. Cultivars at these sites varied in the level of vegetative flushing prior to panicle emergence in May-August and flowering in spring. Paclobutrazol reduced flushing and increased flowering in 5 out of 8 orchards, maintained dormancy and reduced flowering in 1 orchard, and had variable effects in 2 orchards, depending on the method of application. The maximum level of flowering in paclobutrazol treated trees occurred when the control trees bloomed moderately (40-60% of terminal branches). The responses were sometimes weak when the trees were very vigorous (<30% bloom). Paclobutrazol had no significant effect or reduced flowering of heavily blooming (70-100% bloom) trees. Paclobutrazol had only a small effect on panicle development, fruit set and fruit quality at most sites. Yield reflected the flowering response to paclobutrazol, except when yields were lowered by excessive male flowering or bird damage to the fruit.