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How to Manage Pests

UC Pest Management Guidelines

Aster leafhopper adult.

Floriculture and Ornamental Nurseries


(Reviewed 3/09, updated 3/09)

In this Guideline:


Symptoms of phytoplasma (previously known as mycoplasmalike organisms) diseases include yellowing and dwarfing, distorted foliage, and the abnormal production of shoots. Flowers may not develop normally and are often replaced by green leafy structures.


Phytoplasmas are microscopic organisms that are somewhat smaller than bacteria. They do not have a cell wall as do bacteria. The cytoplasm is bounded by a three-layered membrane.

For many years the aster yellows phytoplasma was considered a virus. This phytoplasma is vectored by leafhoppers, in which it can multiply, and has a very wide host range. In general, phytoplasmas are vectored by leafhoppers, plant hoppers, and psyllids and invade the phloem of infected plants.


Virus Transmission Ornamental hosts Crop plant hosts Weeds and native plant hosts
Aster yellows (aster yellows phytoplasma) leafhoppers alyssum, calceolaria, calendula, china aster, chrysanthemum, cineraria, daisies, delphinium, gladiolus, gloxinia, gypsophila, larkspur, petunia, statice, sweet william, tagetes, veronica, zinnia, and many others buckwheat, carrots, celery, lettuce, onion, parsley, parsnip, potato, safflower, spinach, tomato, and many others California poppy, dandelion, plantain, and many others


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
S. T. Koike, UC Cooperative Extension Monterey County
C. A. Wilen, UC IPM Program, UC Cooperative Extension San Diego County
Acknowledgment for contributions to Diseases:
R. D. Raabe, (emeritus) Environmental Science, Policy, and Management (ESPM), UC Berkeley
A. H. McCain, (emeritus) Environmental Science, Policy, and Management (ESPM), UC Berkeley
M. E. Grebus, Plant Pathology, UC Riverside

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