Effects of covering the canopy during spring on flowering and fruit quality in citrus

Abstract

In citrus farming in Japan, less than 1% of fruit acidity determines the timing of harvest. Therefore, high acidity results in a delay of harvest, which affects plans for shipment and marketing. This study aims to develop a technique for the production of citrus fruits with low acidity. We investigated the effect of covering the canopy with a transparent polyethylene sheet during spring and fruit quality at harvest in three citruses, ‘Aoshima unshu’, ‘Shiranuhi’, and ‘Setoka’. In all three citruses investigated, the timing of sprouting and flowering moved forward but the weight and the acidity of fruits at harvest was differently affected. In ‘Aoshima unshu’ and ‘Setoka’, fruits of the canopy-covered trees were heavier than those of the non-covered trees. In ‘Shiranuhi’, there was no significant difference in the weight of fruits from the canopy-covered and non-covered tree. In ‘Shiranuhi’ and ‘Setoka’, the acidity in fruits of the canopy-covered trees was lower than those of the non-covered trees. In ‘Aoshima unshu’, there was no significant difference between the acidity in fruits from the canopy-covered and non-covered trees. The results suggest that this method can be used to produce fruits with low acidity in ‘Shiranuhi’ and ‘Setoka’ citruses.