Description: Spores on diseased twigs ooze out in little tendrils in moist weather, to be spread by splashing water or insects. Entrance is through unbroken tissue as well as wounds. The stem is killed above and below the point of entrance. (25-004) Description: Leaf spots on trees may be caused by insects, toxic gasses, bacteria, and fungi. The characteristic symptom is the formation of dead areas in the leaf. The areas vary in size and shape. (25-005) Description: Depending on the identity of the infecting fungus, needles begin to turn yellow-brown by winter or early spring. Later, the browning progresses, and fungal fruiting bodies are produced. These small, black, fruiting bodies may be bordered by brown or yellow margins, or both. In the more advanced stages, the tree has a scorched appearance. The fungus can be identified only after examining the spores microscopically. (25-006) Description: Powdery mildew is caused by several genera of fungi. Many occur on hardwoods, attacking leaves or occasionally fruits and young twigs. They are unknown on conifers. Usually the damage is slight except when young trees, particularly sprouts, are attacked. They are mostly confined to the upper of lower surface of leaves, forming a white, superficial, cobweb like growth of hyphae. (25-007) Description: Mostly present in nurseries. There may be some curling and malformation of the leaves, often with a fern-leaf effect. A yellow strain of the virus causes a striking yellow mottling of leaves.
Description: Spores on diseased twigs ooze out in little tendrils in moist weather, to be spread by splashing water or insects. Entrance is through unbroken tissue as well as wounds. The stem is killed above and below the point of entrance. (25-004) Description: Leaf spots on trees may be caused by insects, toxic gasses, bacteria, and fungi. The characteristic symptom is the formation of dead areas in the leaf. The areas vary in size and shape. (25-005) Description: Depending on the identity of the infecting fungus, needles begin to turn yellow-brown by winter or early spring. Later, the browning progresses, and fungal fruiting bodies are produced. These small, black, fruiting bodies may be bordered by brown or yellow margins, or both. In the more advanced stages, the tree has a scorched appearance. The fungus can be identified only after examining the spores microscopically. (25-006) Description: Powdery mildew is caused by several genera of fungi. Many occur on hardwoods, attacking leaves or occasionally fruits and young twigs. They are unknown on conifers. Usually the damage is slight except when young trees, particularly sprouts, are attacked. They are mostly confined to the upper of lower surface of leaves, forming a white, superficial, cobweb like growth of hyphae. (25-007) Description: Mostly present in nurseries. There may be some curling and malformation of the leaves, often with a fern-leaf effect. A yellow strain of the virus causes a striking yellow mottling of leaves.
FSVeg_Cat25_FoliageDiseases.docx