柑桔黑點病之生態研究

Ecological Study of Citrus Melanose Caused by Diaporthe Citri

本省柑桔黑點病的發生，西部以苗栗以北地區，東部以成功以北地區發生嚴重；中部輕微，南部只在竹崎山區葡萄柚上發病。同一柑桔樹不同方向之發病度間並無差異。就柑桔植株高度而言，下層發病較諸上層嚴重。樹冠外層發病較內層為多，但差異不顯著。在關西調查不同種類柑桔之發病界以柳橙較為嚴重，椪柑、桶柑次之，以柑桔幼苗做接種試驗，其潛伏期為3-5日，柳橙3日、椪柑4日、桶柑5中。在田間調查不同葉齡的病情形，當抽梢後6週，葉片呈濃綠色和硬化，則不再受感染。後期感染調查，可知至11月上旬前，仍有後期感染發生。

Citrus melanose occurs in varying proportions throughout the citrus region of Taiwan. It is a more serious disease in the northern area than in other places. No relationship was found between direction within, citrus canopy and melanose incidence, outer/inner canopy of citrus tree and melanose severity. Significantly, more melanose incidence occured in the skirt of citrus canopy than in the top. Liucheng variety had the most melanose susceptibility compared with Ponkan and Tankan. The incubation period of melanose varied with different citrus varieties from three to five days. After spring shooting, no infection occured six weeks later. Latter infection was found in autumn shoot and fruit from September to November.