| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Black Knot |
Dark-brown to black,
hard swellings form on twigs and branches. At first these
galls are small but continue to enlarge each year, becoming
very rough, and, each spring, become covered with dark, olive-green,
felty growth. Branches may be girdled and die. |
Apiosporina morbosa |
Prune and destroy galls, cutting several inches
below the gall whenever they are found but especially during
dormancy. Remove unwanted Prunus
species from the area. |
| Brown Rot |
Flowers collapse and brown quickly. Small cankers
form on twigs and gum oozes out. Ripening fruits brown and shrivel
as they become covered with tan to gray masses of spores. While
many fruits fall, some shrivelled mummies are left on the tree. |
Monilinia fructicola |
Apply chlorothalonil, cupric hydroxide, triforine,
ziram, or propiconazole when blossoms first open and again at
70 to 90% bloom. |
| Coccomyces Leaf Spot |
Circular purple to reddish-brown spots up to
1/8 inch in diameter form on the leaf early in the summer and
more spots develop as the season progresses. Spots may fall
away leaving a shot hole appearance. Infected leaves yellow
and fall prematurely. |
Blumeriella jaapii
(Coccomyces) |
On severely affected plants, apply mancozeb +
thiophanate methyl, myclobutanil, or propiconazole as leaves
emerge in the spring. |
| Necrotic Ringspot |
Leafing out is delayed in the spring on individual
branches or the entire tree. Leaves are smaller than normal
and few in number. Expanding leaves have light-green spots up
to 1/4 inch in diameter and dark ring and line patterns. Leaf
margins are wavy and blades are rough. Spots on the leaf die
and fall out. Bark splitting and branch dieback occurs on severely
affected plants. |
Necrotic ringspot virus |
This virus can be transmitted mechanically, through
grafting, through seed and in pollen. Destroy infected trees.
Plums and other stone fruits are also susceptible. |
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