| To improve the prevention and mitigation capacity for low-temperature freeze damage during apple flowering in Yan’an, this study investigated integrated technologies for comprehensive control of flowering-stage freeze injury in Yan’an apple orchards. The results showed that, over the past 30 years, low-temperature events occurred most frequently during April 11-17 in Yan’an (6.66 events per decade). After 2010, flowering-stage freeze damage occurred approximately once per year, and severe events occurred once every 2.3 years. Spatially, the northwestern region had the highest risk (approximately once per year; severe events once every 2.1 years). The southern region also showed a relatively high risk (once every 1.3 years; severe events once every ~3.3 years), whereas the central region was lower (once every 1.7 years; severe events once every ~5 years). The eastern region had the lowest risk (once every 4.3 years; severe events once every ~10 years). In mountainous orchards, full-orchard straw mulching combined with cell-awakening agents showed the best protection for ‘Red Fuji’ during flowering, increasing fruit set and inflorescence fruit set by 27.56% and 40.41%, respectively, compared with full-orchard straw mulching alone. Three additional treatments—full-orchard straw mulching combined with Guo’ao antifreeze agents, bio-complex enzymes, or chitosan—also improved performance. Fruit set increased by 16.75%, 9.90%, and 6.69%, respectively, and inflorescence fruit set increased by 27.19%, 16.38%, and 8.18%, respectively, relative to full-orchard straw mulching alone. Open-field application of cell-awakening agents showed relatively limited efficacy, increasing fruit set and inflorescence fruit set by 10.38% and 6.06%, respectively, compared with the open-field control. Half-coverage shade nets combined with bio-complex enzymes was the least effective treatment, increasing fruit set by only 5.32% compared with half-coverage shade nets alone. For ‘Red Fuji’ grafted on M26 interstock, several measures reduced flowering-stage freeze damage, including full-coverage shade nets combined with Xinong antifreeze agents, plant inducers, edible glucose, or cell-awakening agents, and full-orchard straw mulching combined with cell stimulants, open-field plant inducers, or Xinong antifreeze agents. Compared with the water control, fruit set increased by 11.13%, 10.93%, 8.99%, 8.67%, 9.89%, 13.35%, and 10.46%, respectively. It is recommended to develop integrated technical strategies, including full-orchard straw mulching, installing full-coverage shade nets, and applying antifreeze agents, to mitigate flowering-stage low-temperature freeze damage in Yan’an apple orchards. |
