دانلود پاورپوینت بیماری‌های cucumber

اختصاصی از اس فایل دانلود پاورپوینت بیماری‌های cucumber دانلود با لینک مستقیم و پر سرعت .

Powdery Mildew

caused by the fungus Erysiphe cichoracearum, affects cucumber, muskmelon, pumpkin, and squash. It is caused by a fungus that appears as a white powdery growth on leaves. Crown leaves are affected first and may wither and die. The fungus can be introduced on greenhouse-grown plants or by wind from areas with relatively warm winter climate where the fungus can overwinter. Disease development is favored by high temperatures

Downy Mildew

on cucumber and muskmelon is caused by the fungus Pseudoperonospora cubensis. Irregularly shaped yellowish to brown spots appear on upper sides of leaves, usually at the center of plants. Under moist conditions, a purplish mildew develops on the underside of leaf spots. Leaves die as spots increase in size. Spread is rapid from the crown toward new growth. The causal fungus overwinters in areas with a relatively warm climate and can be introduced to other areas by wind. Moist conditions favor disease development.

Target Spot

caused by Corynespora cassiicola, is similar to downy mildew in appearance. Leaf spots begin as small yellow flecks which become angular or as circular spots with light brown centers and dark brown spots. Spots vary from 1/8 to 3/8 inch in diameter. Lesion coalescence may result in large areas of dead tissue, which may shred and fall out.

Cercospora Leaf Spot

caused by Cercospora citrullina, affects cantaloupe and watermelon. Leaf spots are small, dark brown to black with a white center, and may have a yellow halo.

Alternaria Leaf Spot

ncaused by the fungus Alternaria cucumerina, occurs primarily on muskmelons but also on cucumbers and other cucurbits. Leaf spots are small, circular, and water-soaked at first, and then expand up to 1/2 inch in diameter with dark concentric rings within the spots. Spots coalesce to affect large areas of leaves and cause defoliation that begins on crown leaves. This disease-causing fungus overwinters on and in seed, as well as in residue from diseased plants. Fungus spores (reproductive structures) are spread by wind, by running and splashing water, on workers, and on tools and implements. Weak and senescing plants are more susceptible to Alternaria leaf spot than are vigorous plants.

شامل 20 اسلاید powerpoint