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Aster Leafhoppers
Adult Aster Leafhopper can be found in grassy areas and moving into some small grain fields. They are the grayish looking leafhoppers active in field borders. If you look closely, six spots on the top of the head are visible.
The Aster leafhopper migrates into the region AND overwinters as an egg in grass leaves. Typically, the migrating population of adults from southern states are the ones with the greatest risk of carrying AYP and they are the primary contributor to AYP transmission to hosts. The local population typically has a lower level of infectivity. Factors that contribute to infectivity are: feeding on AYP infected plant; and, an incubation period of 2 to 3 weeks before the AYP can be transmitted. Adults migrating from southern states are more likely to be AYP carriers because of infected host plants where they originated and they have the necessary time needed for AYP to replicate itself in the insect.
Aster yellow infections are very difficult to predict. Risk of problems relates to the size of the insect population and what level of infection is present. The economics of control to try and prevent AYP are not very good for most field crops. High value vegetable crops, such as carrots, should be monitored and treated when aster leafhopper is present. In this case, the insect is controlled to limit transmission. Once AYP is acquired by a plant, there is nothing that can be done. Symptoms require a week or more to appear in infected plants. Typically, a longer time is required for symptoms to appear in older plants. The later the infection, the less impact on the overall health of the plant. Therefore, later planted crops are at greater risk to AYP.
Over 300 species of plants have been identified as hosts of AYP. The vegetable crops (carrots, lettuce, celery) get most of the attention because of their production value. Other plants infected include grains (oats, barley, wheat, rye) and weeds (quackgrass, lambsquarters, sowthistle, dandelion). The aster leafhopper also moves the Oat blue dwarf virus to small grains.
Because of so much uncertainty about infection and poor economic incentive to control the vector, treatment has not been encouraged for field crops and small grains
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