How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS AND SIGNS

Symptoms of diseases caused by mycoplasmalike organisms include stunted growth, chorotic or reddened leaves, leafroll, reduced numbers of subterranean tubers, and the production of aerial tubers. Some plants exhibit witches'-broom symptoms, i.e., the proliferation of many small shoots and leaves. Symptoms may be confused with damage caused by psyllid insects and, in some cases, with leafroll virus.

COMMENTS ON THE DISEASES

These diseases are uncommon in California. Beet leafhopper transmitted virescence agent is transmitted by the beet leafhopper , Circulifer tenellus; western aster yellows is transmitted by another leafhopper, Macrosteles fascifrons. Both mycoplasmalike organisms occur in other herbaceous plants. Both are transmitted through tubers. The incidence of the disease is dependent on the abundance of the leafhopper vectors and the reservoir of the mycoplasmalike organisms.

MANAGEMENT

Although these diseases rarely cause economic damage in California, they are often found in fields with weedy edges or with weedy areas nearby. Controlling weeds near potato fields helps to prevent development of these diseases.

PUBLICATION

UC IPM Pest Management Guidelines: Potato
UC ANR Publication 3463
Diseases
R. M. Davis, Plant Pathology, UC Davis
J. Nuñez, UC Cooperative Extension, Kern Co.
B. J. Aegerter, UC Cooperative Extension, San Joaquin Co.
Acknowledgment for contributions to the disease section:
C. Smart, Plant Pathology, UC Davis

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