Foliar Fertilization as An Alternative to Hand Thinning Fruit in Chlorate Treated Dimocarpus Longan Lour. Trees in Hawaii

Longan, Dimocarpus longan Lour, is a member of the Sapindaceae, a family that also includes lychee, and rambutan.  The discovery of potassium chlorate (KClO₃) induced flowering solved the problem of alternate bearing and enabled the grower to produce off-season longan. Chlorate treatments commonly induces flowering in 90 to 100% of the terminals which require fruit thinning when fruits are 6-12 mm.  Fruit thinning is a very labor intensive process consisting of the removal of 1/2 to 2/3 of each panicle. Here we describe a comparison of sequential applications of foliar fertilization during fruit development with hand thinning of fruiting panicles on two longan cultivars, ‘Egami’ and ‘Biew Kiew’.  Preliminary results suggest that foliar fertilization was comparable to hand thinned fruiting panicles in a low bearing fruit cultivar such as ‘Biew Kiew’ longan. However, in a heavier bearing cultivar such as ‘Egami’, there was a greater incidence of fruit cracking and unmarketable under-sized fruits in the foliar fertilized trees.  Differences in titratable acids, peel thickness, aril firmness, disease incidence and postharvest quality were also observed between the foliar fertilized and the hand thinned fruiting panicles.