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Leaf spots can vary in size, shape, and color depending on the age and type of the cause or pathogen. Plants, shrubs and trees are weakened by the spots on the leaves as they reduce available foliar space for photosynthesis. Other forms of leaf spot diseases include leaf rust, downy mildew and blights. [4]
This mycelial layer may quickly spread to cover all of the leaves. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant.
White rust is a disease in plants caused by the oomycete Albugo candida or one of its close relatives. Plants susceptible to this disease generally include members of the Brassica family. [ 1 ] White rust has been known to cause agricultural losses in fields cultivating members of this family including broccoli , cauliflower , and Indian ...
Leaves are exstipulate, alternate, simple palmately lobed or palmately compound. The flowers are unisexual , with male and female flowers on different plants ( dioecious ) or on the same plant ( monoecious ).
Zucchini yellow mosaic virus (ZYMV) is an aphid-borne potyvirus, regarded as a major pathogen of cucurbits in most regions of the world where these crops are cultivated. ZYMV affects all cucurbits including pumpkins , squashes , [ 1 ] vegetable marrows , courgettes , melons , watermelons , cucumbers , gherkins and various gourds especially ...
The black spots can become about 5 millimeters in diameter. [1] As the season continues, the tissue around the original spot may become necrotic. [4] In severe cases of the disease there is premature shedding of leaves, blight of young leaves and shoots, and complete defoliation early in the fall. [1] Fruits that are infected become crumpled. [1]
Growing marrow Flower of marrow. A marrow is the mature fruit of certain Cucurbita pepo cultivars used as a vegetable. The immature fruit of the same or similar cultivars is called courgette (in Britain, Iran, Ireland, France, the Netherlands, Singapore, Malaysia and New Zealand) or zucchini (in North America, Japan, Australia, the Czech Republic, Italy, Germany and Austria). [1]
Peach tree leaves displaying various stages of the shot hole disease: brown spots on the leaf with conidium holders in the middle (center) that eventually fall off, leaving BB-sized holes behind (left) Shot hole disease of apricot leaves. The fungal pathogen Wilsonomyces carpophilus affects members of the Prunus genera. Almond, apricot ...