Abstract
Requirements of overwintering colonies of honey bees are strong, vigorous colonies with abundant winter stores (90 lb (40.8 kg) honey in October) in the proper position in the hive. Winter consumption of honey and its effect on colony yields the following season were calculated for 1,034 colonies over 8 years and show an average yield of 49 lb (22.3 kg) more honey for colonies that consumed more winter stores than the average from October to April.
Cessation of brood rearing in August, September, and October resulted in corresponding reduction in production the following summer of 141, 106, and 60 lb (64, 48.1, and 27.2 kg) compared to colonies allowed to rear brood into late fall. A test conducted during two winters using cutaway hive bodies with exposed combs emphasized the importance of wind protection for winter survival.
Key words: honey bees, overwintering, combs, package bees, queens, beekeeping management, and brood-rearing.
Overwintering Of Honey Bee Colonies
Production Research Report No. 169
On January 24, 1978, four USDA agencies-Agricultural Research Service (ARS), Cooperative State Research Service (CSRS), Extension Service (ES), and the National Agricultural Library (NAL)-merged to become a new organization, the Science and Education Administration (SEA), U.S. Department of Agriculture.
This publication was prepared by the Science and Education Administration's Federal Research staff, which was formerly the Agricultural Research Service.
Science and Education Administration
UNITED STATES DEPARTMENT OF AGRICULTURE
Washington, D.C. May 1978
Overwintering Of Honey Bee Colonies
FLOYD E. MOELLER 1
Introduction
Honey bees, Apis mellifera L., are kept by man in bee hives, but bees are not domestic animals in any sense of the word. Man adapted his handling and management of these insects by fitting his methods to meet their natural behavior. Bees are no different in their needs or behavior today than were the wild honey bees in the forests at the time of the cave man. When bees swarm from modern hives, they readily return to their wild condition. They have been on earth since the Jurassic period, 160 million years ago, and have survived without man's help. The ideal conditions for winter survival in man's hives must thus approximate what is best in nature.
An analogy made by the late Dr. Farrar (5)2 stated that a honey bee colony is in reality an organism and that the colony lives from now on, unless the victim of disease, starvation, or catastrophe, whereas individual bees of the colony die or are replaced continuously, as are the cells of any living organism. Reproduction of this colony organism is by swarming.
Honey bees were brought to the Americas by early European immigrants. The bees soon escaped from the settlements, went into the wilds of the new world, and lived in hollow trees and caves. When left to their own resources they are adaptable and have little trouble surviving severe winters. Only when man interferes do problems develop.
Bees build combs in many and varied cavities: hollow trees, between the studs in walls of buildings, attics, caves, or any suitable shelter. The main purpose in choosing such enclosures is to provide the colony with protection from winter winds. No attempt is made to heat or control the temperature of the chosen cavity.
__________
1 Research entomologist, Bee Management and Entomology Research, Science and Education Administration, Madison, Wis. 53706
2 Italic numbers in parentheses refer to Literature Cited, p. 14.
Perhaps no other subject in beekeeping management has been discussed and argued as much as methods of overwintering honey bee colonies. Many northern beekeepers over the years have killed their colonies in the fall and depended on package bees for spring replacement. With higher honey prices, many southern package bee producers are turning to honey production. Intense interest is expressed by beekeepers in overwintering colonies of bees, largely because of the unavailability of package bees and queens and high prices.
The package bee colony, 2- or 3-lb (1- or 1.5-kg) size, requires about 11 to 12 weeks to reach maximum population (6). This is governed by the length of time required to develop a bee from the time the egg is laid to emergence (20 days), by the longevity of the bees (30 to 35 days), and by the amount of brood a given population can support (3, 7). A package of bees installed May 1 will consequently reach peak population about August 1. This means that if a major honey flow occurs June 15 to August 1, the colony is building its population on the flow and does not store a maximum crop.
A properly managed overwintered colony reaches its peak June 15 (at the start of the flow) and is capable of maximum production. For this reason, overwintered colonies are preferred. In areas where a maximum crop from an overwintered colony is 250 lb (113.6 kg), the package colony may produce only 80 to 100 lb (36 to 46 kg).
Bees store pollen and honey during the active summer period. This cache of food stored in vertically hanging combs is slowly consumed during the winter. Brood rearing begins about the first of January, and the brood area expands as food and exterior temperatures permit. In the area occupied by brood, the temperature is maintained at about 92° to 93° F (33° C).
At the outer periphery of the roughly spherical cluster occupying the interspaces of the combs, the bees are tightly packed to form an insulating band or shell. The outer edge of this cluster never falls below 43° F (6.11° C) (10) and is usually in the mid-50° (12-13°) range. If the body temperature of a bee falls to 42° (5.56° ), it loses the power of motion and will drop. At 28.5° (1.94°) the body tissue freezes solid. Thus, to maintain life the temperature cannot go below 43° (6.11°).
In the remainder of the hive space not occupied by bees, the temperature falls just as low as the outside. Colonies that build combs in such exposed places as on limbs of trees cannot withstand the cold, piercing winds of northern climates and will not survive. Thus, the main purpose for seeking the confines of a cavity seems to be wind protection.
Requirements for Good Overwintering
Colony strength and condition
A colony population of adequate strength for winter is a prime requisite. At the close of brood rearing in November, a colony of suitable population should fill at least two standard 10-frame hive bodies from wall to wall and top to bottom at a clustering temperature of about 40° F (4.44° C).
Smaller colonies should be united, and only first-class colonies should be overwintered. A poor policy is to attempt to overwinter subnormal or weak colonies, because they seldom will survive. Weak colonies that perish in late winter or early spring probably will be laden with nosema disease. As they are dying, they defecate nosema-laden feces on the combs and equipment, adding difficulty to replacement with package bees. The potential winter loss is best taken at the start of overwintering to keep the equipment clean and conserve honey. In the spring, strong, overwintered colonies can easily be divided and colony numbers doubled or trebled.
The age of the bees going into winter is as important as population size. Late summer and fall brood rearing should be encouraged. This can be accomplished by using young queens and providing ample pollen and honey. Young queens of the current year will lay eggs later into the fall than old queens.
An adequate pollen supply in late summer is necessary to support this late brood rearing, and in most areas pollen is usually available. If a colony has a poor, old, or failing queen, or if the bees have been queenless for a prolonged period in late summer, the population may have a higher than normal proportion of old bees as it goes into winter. When this situation occurs, the population size may look adequate in late fall, but, as winter progresses, the population may shrink faster than winter brood-rearing can compensate, eventually resulting in a colony loss. Such weak colonies may become still further weakened by nosema disease and may perish.
Two tests conducted at Madison, Wis., illustrate the effect of late fall brood-rearing on overwintering success and honey production the following season. At one location, groups of 12 to 13 colonies each, all of the same hybrid stock, were used in tests in which brood-rearing was curtailed early and late by caging queens at different intervals. Queens of one group were caged on August 15, a second group on September 15, and a third group on October 15; the queens of the fourth group were not caged. All queens were released on December 15. The same test was repeated the next winter using groups of 11 and 12 colonies, all of the same hybrid stock. In this test, all queens were released on November 15.
In March when pollen supplement was fed, colonies with queens caged in mid-September and those caged in mid-October had good populations. Those with August curtailment of brood-rearing were noticeably weaker. After brood-rearing expanded in May, these relative population differences persisted.
Requirements of overwintering colonies of honey bees are strong, vigorous colonies with abundant winter stores (90 lb (40.8 kg) honey in October) in the proper position in the hive. Winter consumption of honey and its effect on colony yields the following season were calculated for 1,034 colonies over 8 years and show an average yield of 49 lb (22.3 kg) more honey for colonies that consumed more winter stores than the average from October to April.
Cessation of brood rearing in August, September, and October resulted in corresponding reduction in production the following summer of 141, 106, and 60 lb (64, 48.1, and 27.2 kg) compared to colonies allowed to rear brood into late fall. A test conducted during two winters using cutaway hive bodies with exposed combs emphasized the importance of wind protection for winter survival.
Key words: honey bees, overwintering, combs, package bees, queens, beekeeping management, and brood-rearing.
Overwintering Of Honey Bee Colonies
Production Research Report No. 169
On January 24, 1978, four USDA agencies-Agricultural Research Service (ARS), Cooperative State Research Service (CSRS), Extension Service (ES), and the National Agricultural Library (NAL)-merged to become a new organization, the Science and Education Administration (SEA), U.S. Department of Agriculture.
This publication was prepared by the Science and Education Administration's Federal Research staff, which was formerly the Agricultural Research Service.
Science and Education Administration
UNITED STATES DEPARTMENT OF AGRICULTURE
Washington, D.C. May 1978
Overwintering Of Honey Bee Colonies
FLOYD E. MOELLER 1
Introduction
Honey bees, Apis mellifera L., are kept by man in bee hives, but bees are not domestic animals in any sense of the word. Man adapted his handling and management of these insects by fitting his methods to meet their natural behavior. Bees are no different in their needs or behavior today than were the wild honey bees in the forests at the time of the cave man. When bees swarm from modern hives, they readily return to their wild condition. They have been on earth since the Jurassic period, 160 million years ago, and have survived without man's help. The ideal conditions for winter survival in man's hives must thus approximate what is best in nature.
An analogy made by the late Dr. Farrar (5)2 stated that a honey bee colony is in reality an organism and that the colony lives from now on, unless the victim of disease, starvation, or catastrophe, whereas individual bees of the colony die or are replaced continuously, as are the cells of any living organism. Reproduction of this colony organism is by swarming.
Honey bees were brought to the Americas by early European immigrants. The bees soon escaped from the settlements, went into the wilds of the new world, and lived in hollow trees and caves. When left to their own resources they are adaptable and have little trouble surviving severe winters. Only when man interferes do problems develop.
Bees build combs in many and varied cavities: hollow trees, between the studs in walls of buildings, attics, caves, or any suitable shelter. The main purpose in choosing such enclosures is to provide the colony with protection from winter winds. No attempt is made to heat or control the temperature of the chosen cavity.
__________
1 Research entomologist, Bee Management and Entomology Research, Science and Education Administration, Madison, Wis. 53706
2 Italic numbers in parentheses refer to Literature Cited, p. 14.
Perhaps no other subject in beekeeping management has been discussed and argued as much as methods of overwintering honey bee colonies. Many northern beekeepers over the years have killed their colonies in the fall and depended on package bees for spring replacement. With higher honey prices, many southern package bee producers are turning to honey production. Intense interest is expressed by beekeepers in overwintering colonies of bees, largely because of the unavailability of package bees and queens and high prices.
The package bee colony, 2- or 3-lb (1- or 1.5-kg) size, requires about 11 to 12 weeks to reach maximum population (6). This is governed by the length of time required to develop a bee from the time the egg is laid to emergence (20 days), by the longevity of the bees (30 to 35 days), and by the amount of brood a given population can support (3, 7). A package of bees installed May 1 will consequently reach peak population about August 1. This means that if a major honey flow occurs June 15 to August 1, the colony is building its population on the flow and does not store a maximum crop.
A properly managed overwintered colony reaches its peak June 15 (at the start of the flow) and is capable of maximum production. For this reason, overwintered colonies are preferred. In areas where a maximum crop from an overwintered colony is 250 lb (113.6 kg), the package colony may produce only 80 to 100 lb (36 to 46 kg).
Bees store pollen and honey during the active summer period. This cache of food stored in vertically hanging combs is slowly consumed during the winter. Brood rearing begins about the first of January, and the brood area expands as food and exterior temperatures permit. In the area occupied by brood, the temperature is maintained at about 92° to 93° F (33° C).
At the outer periphery of the roughly spherical cluster occupying the interspaces of the combs, the bees are tightly packed to form an insulating band or shell. The outer edge of this cluster never falls below 43° F (6.11° C) (10) and is usually in the mid-50° (12-13°) range. If the body temperature of a bee falls to 42° (5.56° ), it loses the power of motion and will drop. At 28.5° (1.94°) the body tissue freezes solid. Thus, to maintain life the temperature cannot go below 43° (6.11°).
In the remainder of the hive space not occupied by bees, the temperature falls just as low as the outside. Colonies that build combs in such exposed places as on limbs of trees cannot withstand the cold, piercing winds of northern climates and will not survive. Thus, the main purpose for seeking the confines of a cavity seems to be wind protection.
Requirements for Good Overwintering
Colony strength and condition
A colony population of adequate strength for winter is a prime requisite. At the close of brood rearing in November, a colony of suitable population should fill at least two standard 10-frame hive bodies from wall to wall and top to bottom at a clustering temperature of about 40° F (4.44° C).
Smaller colonies should be united, and only first-class colonies should be overwintered. A poor policy is to attempt to overwinter subnormal or weak colonies, because they seldom will survive. Weak colonies that perish in late winter or early spring probably will be laden with nosema disease. As they are dying, they defecate nosema-laden feces on the combs and equipment, adding difficulty to replacement with package bees. The potential winter loss is best taken at the start of overwintering to keep the equipment clean and conserve honey. In the spring, strong, overwintered colonies can easily be divided and colony numbers doubled or trebled.
The age of the bees going into winter is as important as population size. Late summer and fall brood rearing should be encouraged. This can be accomplished by using young queens and providing ample pollen and honey. Young queens of the current year will lay eggs later into the fall than old queens.
An adequate pollen supply in late summer is necessary to support this late brood rearing, and in most areas pollen is usually available. If a colony has a poor, old, or failing queen, or if the bees have been queenless for a prolonged period in late summer, the population may have a higher than normal proportion of old bees as it goes into winter. When this situation occurs, the population size may look adequate in late fall, but, as winter progresses, the population may shrink faster than winter brood-rearing can compensate, eventually resulting in a colony loss. Such weak colonies may become still further weakened by nosema disease and may perish.
Two tests conducted at Madison, Wis., illustrate the effect of late fall brood-rearing on overwintering success and honey production the following season. At one location, groups of 12 to 13 colonies each, all of the same hybrid stock, were used in tests in which brood-rearing was curtailed early and late by caging queens at different intervals. Queens of one group were caged on August 15, a second group on September 15, and a third group on October 15; the queens of the fourth group were not caged. All queens were released on December 15. The same test was repeated the next winter using groups of 11 and 12 colonies, all of the same hybrid stock. In this test, all queens were released on November 15.
In March when pollen supplement was fed, colonies with queens caged in mid-September and those caged in mid-October had good populations. Those with August curtailment of brood-rearing were noticeably weaker. After brood-rearing expanded in May, these relative population differences persisted.
Table 1.-Effect of early termination of brood-rearing in the fall on honey production the following summer, Madison, Wis. |