HPIPM:Aster Yellows

Author: Howard F. Schwartz and David H. Gent

Identification and Life Cycle

Aster yellows is a virus-like disease caused by a phytoplasma, an organism similar to a bacterium. The aster yellows phytoplasma is vectored by the aster leafhopper, an olive-green or straw-colored leafhopper with six dark spots on its forehead. Aster leafhopppers migrate from the south, usually arriving in early to mid June. Serious outbreaks of aster yellows can be caused by large numbers of migrant leafhoppers in the spring, warm weather in May and June, and adequate precipitation and soil moisture. The aster leafhopper will not fly at temperatures below 60°F. Aster leafhopper feeding itself is not economically damaging, but the aster yellows phytoplasma is damaging. Aster yellows affects over 300 crops and weeds, including carrot, celery, cucurbits, potato, sage, tomato, quackgrass, plantain, chickory, knotweed, sowthistle, ragweed, Kentucky bluegrass and wild carrot. The pathogen survives between susceptible crops in alternate hosts or in its vector.

Plant Response and Damage

Typical aster yellows symptoms are phyllody, the transformation of floral parts into leaf-like tissues. Symptoms generally appear on scattered plants mid to late in the season. Pods of infected plants are hollow. Aster yellows is seldom of economic concern in the Central High Plains.

Biological Control

No biological control strategies have been developed for aster yellows.

Cultural Control

Plant resistant varieties, if available. Control weeds in and around fields that serve as alternate hosts for aster yellows. Increasing planting population may reduce the incidence of aster yellows.

Chemical Control

Insecticides applied when aster leafhoppers populations are at their peak can reduce the incidence of aster yellows.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.