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Black knot occurs only on the woody parts of trees, primarily on twigs and branches, but can spread to larger limbs and even the trunk. Olive-green swellings from the disease are visible in the late spring; as it spreads and matures, typically by autumn, rough black knots circle and kill affected parts. The knots vary in diameter from one inch ...
genus Nepovirus, Tomato black ring virus (TBRV) Infectious bud failure genus Ilarvirus, Prunus necrotic ringspot virus (PNRSV) Peach mosaic Cherry mottle leaf virus: Peach yellow bud mosaic genus Nepovirus, Tomato ringspot virus (ToRSV)
Many of them cause tree diseases, such as Dutch elm disease and apple blights. Some of the plant pathogenic ascomycetes are apple scab, rice blast, the ergot fungi, black knot, and the powdery mildews. The yeasts are used to produce alcoholic beverages and breads. The mold Penicillium is used to produce the antibiotic penicillin.
Viral diseases; Bare twig and unfruitfulness genus Nepovirus, Strawberry latent ringspot virus. genus Tobamovirus, Cucumber green mottle mosaic virus. Line pattern & Necrotic ring spot genus Ilarvirus, Prunus necrotic ringspot virus (PNRSV) Peach mosaic genus Trichovirus, Cherry mottle leaf virus (CMLV) Plum pox (= Sharka)
Taphrina pruni is a fungal plant pathogen of blackthorn (Prunus spinosa) that causes the pocket or bladder plum gall, a chemically induced distortion of the fruit (sloes), producing swollen on one side, [1] otherwise deformed and flattened fruit gall without a stone. [2] The twigs on infected plants may also be deformed with small strap-shaped ...
Brachycaudus helichrysi is a serious pest of stone fruits. It forms dense colonies on the underside of the leaves of the primary host causing curling, [4] twisting and distortion of the foliage, the shedding of flowers and the dropping of young fruit. [8] It is one of several species of aphid that can transmit the virus that causes plum pox. [8]
The disease spreads most quickly during hot, wet weather and is dormant in the winter when temperatures drop. [citation needed] The pathogen spreads through the tree from the point of infection via the plant's vascular system, eventually reaching the roots and/or graft junction of the plant. Once the plant's roots are affected, the death of the ...
A fungus in the genus Taphrina often attacks the plums; the young ovaries swell, often much larger than full grown plums, become hollow and often persist on the tree in winter. Known as "plum pockets", they appear pale green, leathery to the touch, and hollow with the exception of a few fibrous bands. The disease reduces regeneration of the plums.