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Bacterial
Canker (bacterium - Psuedomonas syrinigae pv. syringae): This
bacterium causes cankers, gummosis, and shoot blight (photo).
Sunken lesions appear in the spring with gummosis. Cracks and cankering follow,
resulting in a girdled stem. The foliage becomes yellow, curled, and withered.
Wet spring weather can result in shoot blight and a small angular leafspot.
(photo)This is usually
only a problem in young orchards. Use resistant F12-1 Mazzard rootstock. Remove
girdled branches. Spray with copper hydroxide in October and January. This bacterium
also attacks peaches. See the peach section
for more detail.
Black Knot (fungus - Apiosporina morbosum): Black knot is a very conspicuous and common disease that is also found on apricots and plums. Large, rough black galls form on the twigs.(photo) Twigs may die beyond the galls. No chemical control is recommended. Infected limbs should be removed.
Brown Rot (fungus - Monilinia fructicola and Monilitia laxa): These fungi cause blossom blight, twig blight, and fruit rot. See the section on Peaches - Brown Rot for more detail. Control by fungicide application and sanitation.
Cotton Root Rot (fungus - Phymatotrichum omnivorum): (See Cotton Root Rot section.)
Crown Gall (bacterium - Agrobacterium tumefaciens): Warty tissue masses or galls may form on the roots, at the root collar, or anywhere on the stem. No practical controls are available.
See Crown Gall for more detail.
Leafspot
(fungus - Wflsonia hiemalis): This is the most common and most damaging
leaf disease of cherries. It is most prevalent during rainy springs. The reddish
spots drop out leaving circular holes in the leaves.(photo)
With severe infection, defoliation may follow the appearance of the "shot hole"
symptom. This disease can be controlled with foliar fungicides.
Little Cherry (virus): Fruit are half size. Flowering cherry acts as a reservoir for the virus. Buy only virus-free trees from reputable nurserymen and remove infected trees when they are discovered.
Littleleaf: This is a condition in the West caused by a lack of zinc.
Mushroom Root Rot (fungus - Armillaria mellea): (See Mushroom Root Rot section.)
Necrotic Rusty Mottle (virus): Foliage and blossoms are delayed in the spring. Brown necrotic or rusty chlorotic spots develop on the leaves, often falling out to leave shot holes.(photo) Defoliation may occur. Buy virus-free trees from reputable nurserymen. Virus infected trees should be removed from the orchard.
Rugose Mosaic (virus): General chlorosis of the leaf occurs between mid vein and margin with distortion. Fruit yield is reduced. The fruits become flattened and angular. Remove infected trees.
Rust (fungus - Tranzschelia discolor): Rust also occurs on peach and plum. Yellow spots appear on the upper leaf surface with reddish pustules filled with spores on the lower surface. It can cause premature leaf drop lowering tree vigor. Apply fungicides in late summer and fall.
Rusty Mottle (virus): Many leaves tum bright yellow to red with green islands and drop before harvest. Those that remain have yellow-brown spots with a rusty appearance. The fruit is small, late, and tasteless. Remove diseased trees and select grafting material from virus-free trees.
Shot-hole or Black Leaf spot (bacterium - Xanthomonas pruni): This bacterium also attacks peach and plum. The infected tissue dries up and falls out leaving a one-eighth inch diameter hole. It also causes a canker and gummosis of the stem. See the section on peach diseases for more detail.
Vein Clearing or Sweet Cherry Crinkle (probably genetic): A non-transmissible virus-like disease. Veins clear in localized areas or the entire leaf Margins of the leaves are irregular. Some are elongated with slot-like perforations. Small blisters appear on lower sides of veins, and the upper sides are silvery. Leaves fold along midrib, wilt, and drop in midsummer. Some branches will rosette. Flowers are plentiful, but few will develop into fruit. The fruit will be pointed and flattened on one side with a swollen ridge.
Witches' Broom (fungus - Taphrina cerasi): This fungus causes large numbers of irregular small branches to develop on twigs and larger branches forming a witches' broom. Blossoms develop and the leaves come out on the brooms earlier than on the normal branches. Large numbers of brooms may eventually kill a tree. Cut and burn brooms.
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