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Aster Yellows - Phytoplasma     Whitney Cranshaw, Colorado State University,
www.ipmimages.org
 HOSTS: Vegetables: Carrots, celery, lettuce, parsnips . Flowers: Asters, Echinacea,
and annual flowers such as zinnia. DESCRIPTION:
This
disease causes twisted distorted new growth (including leaf-like
petals) and a yellowing/reddening of leaf tissue; it also causes hairy
roots in carrots. LIFE
CYCLE: Aster
yellows is caused by Phytoplasma spread only by leafhoppers. These pests
overwinter in warmer regions then migrate north. After feeding upon
infected plants, they can then transmit the disease through feeding.
Peak infection periods are in late summer/early fall. CONTROLS:
Control the leafhopper
with pyrethrum plus insecticidal soap. Plant resistant cultivars when
possible. At the Frontier Herb Company Experimental Farm in Iowa,
planting crops in polycultures (beds comprised of several crop species)
has greatly reduced the incidence of aster yellows. |
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