作者：曾惠中
類別：圖書文獻類 - 手稿
材質：紙質
年代：1969~1969
尺寸：長:24.6 x 寬:20.5 (cm)
藏品來源：曾惠中捐贈
登錄號：2019-001-0001-039
藏品描述：本病害於冷涼潮濕的環境下發病，病原菌之孢子柄自寄主植物氣孔突出，著生大量之游走孢子囊，遇高濕則發芽形成游走孢子，隨水分移動或雨水飛濺，造成新的感染，傳播快速，常造成相當嚴重的為害。病原菌可藉種子傳播，亦可在被害植株莖、葉中形成卵孢子殘存於土中，成為翌年之初次感染源。本病主要發生於葉片，尤以幼嫩葉片較嚴重。初期葉片產生黃色褪色斑點，病斑之擴展因受葉脈限制，故呈多角形，病斑部下表皮產生白色棉花狀物。
Downy mildew only infects foliage, a reduction in photosynthetic activity early in plant development results in stunted plants and yield reduction, especially in cucumber. Symptoms on cucumber and squash are angular lesions that are limited by the leaf veins. During periods of leaf wetness from dew, irrigation or rainfall, incipient lesions can become conspicuously water-soaked. This is the earliest symptom produced by the disease, but will disappear as moisture dissipates. Early lesions are light green in appearance and become chlorotic and finally necrotic as host plant cells die.