Environment
There are hardly any conditions that directly impact the development of Aster yellows, but there are a few indirect factors that strongly influence the rate of transmission by the leafhopper. Conditions that favor movement and spread of the leafhopper and encourage feeding assist in the spread of the phytoplasma.
Transcontinental migration begins in the spring when the prevailing winds and jet streams help carry the leafhoppers from their overwintering sites in the South to the Midwest. Upon arrival in the Midwest they begin feeding. The leafhopper may have migrated into the region already carrying the phytoplasma, which it could have acquired from infected plants along the migration or while still in the South. The leafhopper could have also arrived not yet carrying the phytoplasma. If this is the case, it could feed on perennial weeds that are infected to acquire AYP. Weather conditions greatly influence leafhopper flight because they are poor flyers. Temperatures below 15 degrees Celsius or rainfall will temporarily halt their migration and delay the time of infection. The leafhoppers will then feed all summer long until they migrate back to their overwintering sites in the fall.
Weather conditions of the region also greatly influence leafhopper feeding patterns. If conditions are hot and dry plants do not appear as lush and nutrient rich to the phloem feeding leafhopper whereas seasons with abundant rainfall allow the plants to have much more lush growth. This means that hot and dry conditions are less conducive to the spread of Aster yellows than times of abundant rainfall.
In the Western United States, there is no migration of the vector leafhoppers. This allows for transmission of the phytoplasma year round.
Read more about this topic: Aster Yellows
Famous quotes containing the word environment:
“For those parents from lower-class and minority communities ... [who] have had minimal experience in negotiating dominant, external institutions or have had negative and hostile contact with social service agencies, their initial approaches to the school are often overwhelming and difficult. Not only does the school feel like an alien environment with incomprehensible norms and structures, but the families often do not feel entitled to make demands or force disagreements.”
—Sara Lawrence Lightfoot (20th century)
“A positive learning climate in a school for young children is a composite of many things. It is an attitude that respects children. It is a place where children receive guidance and encouragement from the responsible adults around them. It is an environment where children can experiment and try out new ideas without fear of failure. It is an atmosphere that builds children’s self-confidence so they dare to take risks. It is an environment that nurtures a love of learning.”
—Carol B. Hillman (20th century)
“Maturity involves being honest and true to oneself, making decisions based on a conscious internal process, assuming responsibility for one’s decisions, having healthy relationships with others and developing one’s own true gifts. It involves thinking about one’s environment and deciding what one will and won’t accept.”
—Mary Pipher (20th century)