Yellow-fleshed "Sweet Gold" kiwifruit on Jeju Island were studied to examine how irrigation and soil moisture control affected changes in photosynthetic traits and fruit quality during fruit maturation (120 to 170 days after full bloom). Concerning photosynthetic characteristics, the photosynthetic rate decreased by 10-19%, stomatal conductance by 24-47%, and transpiration rate by 8-25%, when compared to conventional irrigation, as irrigation was reduced and soil moisture content decreased. Fruit weight showed a tendency to increase until harvest, and while a lower soil moisture content led to a less pronounced increase in fruit weight, this difference was not statistically significant. The dry matter rate exhibited a similar trend to the change in fruit weight. Sugar content demonstrated a continuous increase after 130 days, with lower irrigation amounts resulting in higher levels of sugar content due to decreased soil moisture. The Hue value (h°) exhibited a continuous decrease after 140 days from full bloom, correlating with declining soil moisture content. After 130 days from full bloom, soluble sugar content increased rapidly while starch content gradually decreased after 150 days from full bloom. However, with conventional irrigation, the increase in soluble sugar content tended to be less noticeable. This study confirmed that in yellow-fleshed ‘Sweet Gold’ kiwifruit, managing irrigation and soil moisture reduction during the ripening period can lead to decreased fruit weight but increased dry matter, sugar content, and expression of flesh color, ultimately enhancing fruit quality and expediting ripening.

In this study, we investigated the effects of the eco-friendly chemical bio-sulfur, on the citrus melanose-causing pathogen, Diaporthe citri, and on the pest, Panonychus citri. In an open field experiment with a plot-scale application of the chemicals: Mancozeb, lime sulfur, lime sulfur + machine oil, and bio-sulfur, the control group showed 70.6% disease severity compared with 10.3% for the Mancozeb-treated group. Among the eco-friendly treatments, disease severity was the lowest for the group treated with lime sulfur + machine oil (32.2%) and was 53.9%, 58.8%, and 58.1% following treatment with lime sulfur, and bio-sulfur diluted 500 and 1000 times, respectively. The proportion of diseased fruit showed similar results, suggesting that bio-sulfur is an effective alternative to lime sulfur. Three days after treatment acaricidal effects on P. citri showed a 197.6% control survival rate whereas the machine oil, and bio-sulfur diluted 500 and 1000 times treatments showed rates of 2.9%, 5.8%, and 9.0%, respectively. After three days, the control value for bio-sulfur diluted 1000 times was 73.2% compared with the values for the machine oil (96.4%) and bio-sulfur diluted 500 times (94.6%) treatments. Therefore, we suggest that additional research is needed on the combined application of bio-sulfur and oils to enhance the additive control effect on citrus melanose and Panonychus citri.

The aim of the present study was to investigate the suppressive effects of the bio-sulfur used by eco-friendly farms on the outbreak of citrus scab. To evaluate the inhibiting effect of bio-sulfur on citrus scab germ tube growth, the citrus scab pathogen Elsinoe fawcettiiwas cultured in PDB and agar media, and germ tube growth was observed after bio-sulfur treatment. At both 40 and 88 h after inoculation, germ tube formation was inhibited by 500-, 1000-, and 2000-fold diluted bio-sulfur, and at dilutions above 4000-fold, germ tube formation was observed, although growth was still inhibited, when compared to untreated cultures. Meanwhile, the occurrence of citrus scab on spring-flush leaves in the field was 40.3% in the untreated control and 5.3, 10.3, 12.3, 15.3, and 24.0% when treated with imibenconazole, 2-4 and 6-6 lime-Bordeaux mixtures, which are also used by eco-friendly farms, 500-fold diluted bio-sulfur, lime sulfur, and 1000-fold diluted bio-sulfur, respectively. The occurrence of citrus scab on citrus fruit was 79.3% in the untreated control and 4.0, 33.8, 42.0, 43.3, 44.8, and 78.0% when treated with imibenconazole, 2-4 lime-Bordeaux mixture, 6-6 lime-Bordeaux mixture, 500-fold diluted bio-sulfur, lime sulfur, and 1000-fold diluted bio-sulfur, respectively. Because citrus scab can infect citrus leaves as early as May, as the spring flush begins, preventative control should be implemented by mid- to late-April, thereby increase disease control and reducing both labor and farming costs.