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On the apple tree, the infections occur on leaves, fruit and young twigs. [4] The brightly colored spots produced on the leaves make it easy to identify. Small, yellow-orange spots appear on the upper surfaces of the leaves, anytime from April to June. [5] These spots gradually enlarge and turn orange or red and may show concentric rings of color.
Possible symptoms produced tend to vary from white gray mottling on field maple to yellow chlorotic spots on hawthorn leaves. [1] There is an Apple Necrotic Mosaic Virus (ApNMV) which is a very similar virus but displays signs of necrosis. [6] Furthermore, in plum trees, ApMV can cause line-pattern symptoms, while in roses, the symptoms are ...
Blister spot Pseudomonas syringae pv. papulans: Crown gall: Agrobacterium tumefaciens: Fire blight: Erwinia amylovora: Hairy root ... Apple scar skin = apple dapple ...
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]
The primary blossom mildew emerges at pink bud stage. Flowers are deformed with pale green or yellow petal and are covered in white mycelium and spores. [4] The secondary mildew may have lesions that appear as chlorotic spots on the upper leaf surface. Symptoms of the secondary mildew also included distorted leaves and premature falling of ...
In late spring, chlorotic spots appear on tree leaves. These develop into brown-black lesions, retaining the yellow border. [4] The lesions continue to grow, and by the end of summer form leaf spots that look like tar. [2] The spot can grow up to 1.5 inches (4 cm) in diameter. [4]
Apple chlorotic leafspot virus ... This virus reduces tree vigor (50% on pear), reduces yield (40% on pear), and causes quality reduction on fruits (if symptomatic).
A. mali can still penetrate the stomates and hydathodes of leaves. [4] As with most pathogens, Alternaria mali resistance involves a gene-for-gene relationship. [4] Apple trees can recognize invading pathogens and mount a defense. [4] Often, the plant may be able to resist the pathogen, even though it has no genetic resistance to same.