SUNBURN PROTECTANT DECREASES THE INCIDENCE OF BULL'S EYE AND WHITE ROTS IN ‘FUJI STANDARD’ AND ‘PINK LADY’ APPLES

ABSTRACT Bull's eye rot (Cryptosporiosis perennans) and white rot () are aBotryosphaeria dothideamong the major apple summer diseases in Brazil. The aim of this study was to evaluate the effect of a protective film consisting of carnauba wax and clay (Raynox®) at doses of 2.5% and 5.0% in infection of C. perennans and B. dothidea in ‘Fuji Standard’ and ‘Pink Lady’ apple cultivars. Apple trees were sprayed five times from December 2007 to March 2008, as predicting of adequate conditions for the occurrence of fruit damage and growth. At harvest, the apples were inoculated with both pathogens and evaluated for incidence of decay. Indifferent to dose, the use of Raynox® reduced the incidence of white rot and bull's eye rot in 67% and 42% in ‘Fuji Standard’, and 43% and 42% in ‘Pink Lady’, respectively. Increasing the dose increased the efficiency of the product for the control of bull's eye rot. At dose of 2.5%, control of bull's eye rot was 19% and 20%, respectively, of ‘Fuji Standard’ and ‘Pink Lady’ apples, while for the same cultivars, but with dose of 5.0%, these values were 65% and 63%. More studies are needed to adjust the dose and application criteria for the sunburn protectant could be recommended.摘要：靶斑腐烂病（Bull's eye rot，Cryptosporiosis perennans）与白腐病（由Botryosphaeria dothidea引起）均为巴西苹果的主要夏季病害。本研究旨在评估由巴西棕榈蜡与黏土制成的保护膜（瑞诺克斯®，Raynox®）在2.5%与5.0%剂量下，对‘标准富士’（Fuji Standard）与‘粉红佳人’（Pink Lady）苹果品种被C. perennans和B. dothidea侵染的防控效果。试验于2007年12月至2008年3月间对苹果树喷施药剂五次，喷施时机依据果实受害与病原菌生长的适宜条件预测确定。收获期对苹果接种两种病原菌后，调查腐烂病发病率。无论剂量高低，使用瑞诺克斯®均可使‘标准富士’的白腐病与靶斑腐烂病发病率分别降低67%与42%，‘粉红佳人’则分别降低43%与42%。提高剂量可提升靶斑腐烂病的防控效率：在2.5%剂量下，‘标准富士’与‘粉红佳人’苹果的靶斑腐烂病防控率分别为19%与20%；当剂量提升至5.0%时，对应防控率分别为65%与63%。后续仍需开展更多研究以优化剂量与施用标准，进而推广该防日灼保护剂的应用。