How to Manage Pests
UC Pest Management Guidelines
Diseases Caused by Phytoplasmas
Beet leafhopper transmitted viresence agent, Aster yellows phytoplasma
In this Guideline:
Beet Leafhopper-Transmitted Viresence Agent
Leaves of infected plants are reddish purple.
Infected plants often bolt prematurely. Flower parts are malformed; petals that
would normally be white are green and the flowers proliferate to form multiple,
compound, leafy umbels. Diseased plants have woody, unmarketable roots with an
excessive number of lateral rootlets.
Aster Yellows Phytoplasma
Leaves of infected plants are twisted, stunted, and yellow. Leaflets may be reduced to short scales.
Flower parts are severely distorted and malformed; umbels are stunted and
yellow green. Most infected plants develop a dense cluster of dwarfed,
chlorotic, upright, adventitious shoots. Infected plants show increased lateral
The beet leafhopper-transmitted viresence agent is transmitted by
the beet leafhopper, Circulifer tenellus. Aster yellows phytoplasma is transmitted by several
species of leafhoppers. Both phytoplasmas have wide host ranges. The level of
infection in carrot fields is dependent on the population of vectors. Disease
incidence may be greater if carrots are planted near areas where weeds and
other plants provide a reservoir for the phytoplasmas and their vectors.
There are no effective controls for these diseases.
UC IPM Pest Management Guidelines:
UC ANR Publication
J. Nunez, UC Cooperative Extension, Kern County
R. M. Davis, Plant Pathology, UC Davis
T. A. Turini, UC Cooperative Extension, Fresno County
Acknowledgment for contributions to Diseases:
B. W. Falk, Plant Pathology, UC Davis
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara County
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