THE EFFECT OF ETHYCLOZATE ON TREE WATER STRESS AND FRUIT QUALITY OF SATSUMA MANDARIN

The fruit quality of Satsuma mandarin strongly depends on drought stress during the maturation period. Most commercial orchards in Japan receive significant amounts of rain during the maturation period. To obtain the highest quality fruit, water vapor-permeable sheets are used to cover the ground (mulching) in approximately 20% of the very early ripening Satsuma mandarin orchards in Japan. However, these sheets are ineffective in citrus fields converted from paddy fields. Chemicals, such as ethyclozate, might be used to improve fruit quality as a substitute for mulching for applying water stress and reducing water uptake through roots. This effect was notable in young trees, but there was no report of effects in mature trees. In this experiment, seasonal changes in the volumetric water content (VWC) in the trunks of mature trees were monitored using time domain reflectometry (TDR) along with the effects of the chemical. The results suggested that VWC decreased in the treated trees from early July immediately after treatment until early September. In addition, coloring began to develop one week earlier, and the Brix increased by about one degree at harvest. These results suggest that the application of ethyclozate in early summer might play a role in applying water stress to improve fruit quality.