However, even if the migration is small, fall weather can still be very important. during a mild fall migrant aphids may continue to arrive and wing aphids from the existing colonies can "flit" about the field, establishing new colonies (red) and more BYD spots.

A mild fall, warm winter, and early spring are the most favorable conditions for aphid / BYD development. Under these conditions aphids will establish new colonies (red spots) by flitting and expand original and new colonies by walking (magenta). These conditions will result in the most widespread BYD epidemics. Also, because BYDV replication within the plants is regulated by temperature, warm winters will result in infected plants being more heavily damaged.

A small fall migration, a short cool fall, a cold winter and a cool spring keep aphid colony numbers and size small and BYD infections at a minimum.

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