Improving Fruit Size and Breaking Alternate Bearing in ‘Wilking’ Mandarins by Ethephon and Other Agents1

Abstract

(2-Chloroethyl)phosphonic acid (ethephon), 200 ppm, and naphthaleneacetic acid (NAA), 350 ppm, sprayed on fruitlets 1 cm in diameter, caused satisfactory thinning of heavily loaded ‘Wilking’ mandarin trees ( Citrus reticulata Blanco) without significant decrease of yield in kg per tree. Individual fruit size was increased 64% with ethephon and by 48% with NAA, increasing profit by about 30% in both cases as compared with hand thinned controls. A summer pruning treatment had similar effects but the increase in fruit size was smaller. Ethephon reduced alternation of bearing and resulted in satisfactory yields the following year on 57% of the treated trees.