Dieback Reality of Apple Trees Resulting from Soil-Borne Fungal Pathogens in South Korea from 2016 to 2019

Recently, the severe dieback of apple trees resulting from soil-borne diseases has occurred in South Korea. The casual agents of dieback were surveyed on 74 apple orchards that had been damaged nationwide in 2016–2019. The number of apple orchards affected alone by Phytophthora rot, violet root rot, and white root rot was 31, 34, and 3, respectively. Also, the total number of mixed infection orchards was 6. Out of 9,112 apple trees affected by dieback, the trees damaged by Phytophthora rot, violet root rot, and white root rot were 3,332, 3,831, and 44, respectively. Moreover, the total number of mixed infection apple trees was 1,905. The provinces mainly affected were Gyeongnam, Gyeongbuk, Chungbuk, and Jeonbuk. The survey on these infected apple orchards will be available to form management strategy for the dieback that had been in- creased by soil-borne fungal pathogens.