Occurrence of zonate leaf blight on Camellia sasanqua in Kagoshima Prefecture and affecting factors

Abstract

In Kagoshima Prefecture, we investigated the damage caused by zonate leaf blight on Camellia sasanqua trees planted in various locations, including parks and roadsides (14 locations) and wild trees in the mountains (7 locations). The occurrence rate and degree of damage varied greatly among survey sites and were remarkably higher for planted trees than for wild trees; however, clear relationships between altitude and occurrence rate or degree of damage were not observed. The occurrence rate and degree of damage were generally similar between 2017 and 2018 for every location. Among planted trees, clusters of regularly pruned planted trees exhibited higher occurrence rates and degrees of damage (indicating greater damage) than those that were left unpruned. Among pruned planted trees, damage was more pronounced in plants receiving ample sunlight than in those receiving less sunlight. Across all surveyed clusters, the greater the relative light intensity, the greater the damage. Conversely, damage was more pronounced when the crowns of adjacent plants were in contact.