The most important late summer nectar flowers are fireweed (Epilobium) and heather (Calluna). Nordic brown bees are especially adapted to collecting heather honey. Honeydew, a sugar-rich secretion of some aphids, might also be available in August, but not every year. Optimising harvesting time with feeding time is sometimes difficult, if the honey flow continues late into the summer. The August varroa control and honeybee feeding must be done in good time before it gets too cold for the bees to be active. They will stop feeding if the temperature during the day is under 5°C.