Apple rust - sporangium stage. |Severity:||2 out of 5|
|Frequency:||3 out of 5| On juniper or eastern red cedar, small
(3/8 to 1 and 3/16 inches in diameter) galls develop throughout
the tree on needles and small twigs. When mature, these galls
swell considerably and repeatedly produce orange, gelatinous
fruiting structures (telial horns) during rainy spring weather.
As spring rains subside, the galls die, which may cause death of
the twig from the gall to the tip. On susceptible apples and
crabapples, tiny yellow spots appear on the leaves after
infection in the spring. As the spots mature, they become
yellow/orange and swollen with a red border, and develop tiny
black dots (spermagonia) in the center of the lesion on upper
leaf surface. By mid-summer, small cup-like structures with
tubes (aecia) are visible on the undersides of mature leaf
lesions. The fungus may also infect fruit and even succulent
twigs of very susceptible apple and crabapple varieties. In
order to survive, the fungus must "move" from one