Studies on the Six-Spotted Leafhopper, Macrosteles Fascifrons (Stål.), and Aster Yellows in Manitoba

Evidence from nymphal and adult counts suggested that adult Macrosteles fascifrons (Stål.) migrate from the south into Manitoba each year, and produce one generation before autumn. Lettuce was shown to be the preferred host over aster, parsley, carrot and flax. Cage experiments showed that head lettuce free from aster yellows virus can be produced when the insect vectors are excluded. Eight varieties of head lettuce were tested for resistance to the disease. Only one variety, Trianon Cos, showed any degree of tolerance. Transmission tests from celery and zinnia indicated the presence in Manitoba of the western strain of the virus.