The disease is transmitted from plant to plant by several species of aphids in a non-persistent fashion, which means that the aphids will only remain infective temporarily. Control strategies for onion yellow dwarf include the planting of disease free bulbs or sets. The use of true seed is even better, because the virus is not transmitted through the seed. New plantings should be separated from areas with infected crops or volunteers. The application of insecticides to control the aphid vectors will do little to control the disease because the virus is transmitted to the plant before the insecticide can act on the aphid.
Some onion varieties are more tolerant of onion yellow dwarf than are others.
Lewis Seeds' pheromone trap near Ursa in western Illinois picked up 6 corn earworm moths between May 24 and 27 and another 4 between May 31 and June 2. Our trap in Champaign has caught a couple of earworm moths in the last week as well, but overall, earworm flight remains light and erratic. IF pheromone traps are capturing earworm moths in your area. When counts exceed 50 to 100 per night and daytime temperatures reach the upper 80s and 90s, treatment intervals for earworm control should be 2 to 3 days. Pounce, Ambush, and Asana are also labeled and effective.