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Ash Yellows - Phytoplasma
 UC - Davis, Pests of the Garden and Small Farm - Puplication #3332
 HOSTS: Ash (Fraxinus). DESCRIPTION: Infected
ash trees show a variety of symptoms. The most dramatic field symptom
is the presence of witches' brooms on the trunk and major limbs. Leaves
on the broom tend to be small and chlorotic; the branches do not have a
dominant shoot but are made up of many shoots. After several years of
minimal growth, leaves will only appear in tufts at the end of branches. LIFE CYCLE: The
disease is caused by a phytoplasma, a prokaryotic organism similar to a
bacteria, but simpler in structure. Phytoplasmas live in the phloem
tissues of trees and infect trees systemically. Insects such as
leafhoppers, spittlebugs, and psyllids are the major carriers of
infection. CONTROLS: Remove
infected trees if badly infected. |
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