Colonies that successfully live through the winter generally have low numbers of adult bees and little brood. In some districts, there may be no brood at all. The aim of spring management is to increase the size of colonies as strong colonies are necessary for good honey production. More honey can be obtained from one colony that contains 50,000 adult bees than from two colonies each containing 25,000 bees.
In early spring, (sometimes late winter depending on seasonal conditions and district), the rate of brood rearing increases, which in turn results in more adult bees. Although this is good for honey production, the expansion of the colony can stimulate the swarming impulse that causes colonies to naturally split to reproduce. This causes the original colony to be weakened for some time.
As soon as colonies begin to expand their brood nests, usually in early to mid-September, inspect the brood for signs (symptoms) of American foulbrood disease (AFB) and other brood diseases. Do this on a relatively warm day when bees are flying well. If AFB is found, or is suspected, reassemble the hive and reduce the entrance to about 50 mm to safeguard against robber bees. Notify an apiary officer of your state/territory Department of Primary Industries straight away as AFB is a notifiable bee disease.
Special thanks to the Rural Industries Research & Development Corporation (RIRDC) for this information, taken with their permission from their publication the Australian Beekeeping Guide.