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】苹果轮纹烂果病（Bull's eye rot，Cryptosporiosis perennans）与白腐病（病原为葡萄座腔菌Botryosphaeria dothidea）均为巴西苹果产区夏季主要病害。本研究旨在评估由巴西棕榈蜡（carnauba wax）与黏土（clay）复配而成的日灼防护膜——雷诺克®（Raynox®），在2.5%与5.0%两种剂量下，对‘富士标准’与‘粉红佳人’两个苹果品种受C. perennans与B. dothidea侵染的防控效果。2007年12月至2008年3月间，研究人员依据果实病害发生与病原菌生长的适宜条件预测节点，对苹果树共喷施5次该防护剂。采收期对苹果接种两种病原菌后，调查其腐烂发病率。无论施用剂量高低，雷诺克®均可降低两种病害的发病率：‘富士标准’苹果的轮纹烂果病与白腐病发病率分别降低67%与42%，‘粉红佳人’苹果则分别降低43%与42%。提高药剂剂量可提升其对轮纹烂果病的防控效率：当剂量为2.5%时，‘富士标准’与‘粉红佳人’苹果的轮纹烂果病防控率分别为19%与20%；而当剂量提升至5.0%时，两个品种的防控率分别升至65%与63%。仍需开展更多研究以优化该防护剂的施用剂量与应用规范，方可推动其正式推广应用。