Archival copy. For current version, see: https://catalog.extension.oregonstate.edu/pnw623 A Pacific Northwest Extension Publication Oregon State University • University of Idaho • Washington State University PNW 623 • January 2011 Evaluating Honey Bee Colonies for Pollination A Guide for Commercial Growers and Beekeepers R.R. Sagili and D.M. Burgett oney bees are accurately described as Contents indispensable pollinators. In the United What is a colony? . 1 States alone, the worth of honey bee H Worker bees . ...................................2 pollination is estimated at $15 billion. Honey bee flight . 2 In this publication, commercial growers who Colony size and efficiency . 2 rent honey bees for pollination and beekeepers who How many to use? . 3 provide pollination services will find information Colony-strength regulations . 3 on honey bee colony strength evaluation, average Disease. 3 number of colonies needed for pollination, basic Amount of comb. .3 honey bee biology in context of pollination, and Amount of brood . ..............................4 pollination contracts. Number of bees . ...............................5 Food requirement . .............................5 The success of honey bees as pollinators is due to A normal queen . ...............................5 certain aspects of their biology. Grade B colonies. .6 • Honey bees forage for nectar and pollen from Colony strength inspections . 6 many thousands of plant species, so they Recommendations for renting bees . 6 efficiently pollinate a wide variety of important Use a contract . .6 food and seed crops. Oregon and Washington colony-strength • While foragers from one hive may visit many regulations . 7 species of plants in a given day, individual foragers Oregon. 7 display flower fidelity or constancy. When a Washington . ...................................8 forager begins collecting nectar or pollen from the flowers of one species of plant, she will continue to visit flowers of only that species for at least one What is a colony? foraging trip and more often for several days or Honey bees are social insects. Look at a colony until the resource is no longer producing nectar of honey bees as a family unit. A colony has a single or pollen. This is important to the plant she visits, queen, who is the sole female reproductive in the as it requires pollen from a flower of the same hive and is the mother of the sexually sterile female species for pollination. workers. Drones (male honey bees) are also present • Honey bee colonies are mobile. Hives are easily in a healthy colony during spring and summer when moved to locations where there are not enough food is abundant. In addition to the adult bees, a native pollinators to adequately pollinate a specific healthy colony also has brood, the collective term crop. for eggs, larvae, and pupae (the immature stages in the life cycle of bees). Ramesh R. Sagili, Extension apiculturist, and D. Michael Burgett, professor of entomology emeritus, Oregon State University. 1 Archival copy. For current version, see: https://catalog.extension.oregonstate.edu/pnw623 The population of a single honey bee colony is not entrance forage earlier than colonies that do not. static. During the course of a normal year, a colony’s Growers in wet regions (e.g., western Oregon) lowest population of adult workers (approximately are advised to rent a relatively higher number of 10,000 to 15,000) is in January and February. The colonies (one extra hive per acre) than suggested in colony can grow to a maximum of 50,000 to 60,000 Table 1 (page 3) as insurance against poor foraging workers by midsummer. Drones typically compose weather. 5 percent of the total adult population in a colony. The control and management of colony growth most Colony size and efficiency frequently depends upon the age and health of the As the worker population increases in a colony, queen, foraging environment, time of year, and skill the proportion of bees old enough for foraging of the beekeeper. increases. As a general rule, smaller colonies send Worker bees out a smaller percentage of their bees as foragers. On the other hand, larger colonies send out not Worker bees are short-lived. During the active only more bees but also a higher proportion of the foraging season (from March to October in the population as foragers. Pacific Northwest), a worker lives about 5 to 6 weeks. The greater value of larger colonies for pollination After an adult worker emerges from a pupal can be illustrated by the amount of honey produced cell, her first 3 weeks are spent inside the colony by colonies of different populations. A colony’s serving as a “house” bee. She goes through a series ability to store surplus honey is a direct result of of tasks that includes cleaning comb, feeding larvae, the number of bees foraging and the amount of secreting wax, building comb, accepting nectar loads forage available — and the foragers are the ones that from foragers, ripening nectar, ventilating the hive, pollinate the flowers. Research has demonstrated and (for a short time) acting as a guard bee at the that: entrance of the colony. One colony of 30,000 bees produces 1½ times When a worker bee is about 21 days old, she • as much honey as the sum of two colonies with begins to take short orientation flights. This marks 15,000 bees each. the beginning of her 2- to 3-week life as a forager bee, seeking nectar and pollen to bring back to the • One colony of 45,000 bees produces 1½ times as colony. much honey as three colonies with 15,000 bees each. Honey bee flight • One colony of 60,000 bees produces 1½ times as Bees must have suitable light and temperature much honey as four colonies with 15,000 bees before they begin foraging. A general observation is each. that stronger, more populous hives begin foraging at The strength of the colonies a grower rents will be a lower temperature than weaker, smaller colonies. influenced by several factors: Even so, honey bees only rarely fly at temperatures 1. Time of year. Colonies rented earlier in the below 55°F. As the outside temperature increases season will not be as strong as the same colonies to about 70°F, the number of bees foraging from a rented later in the season to pollinate another given colony increases. Here’s a guide for relating crop. springtime temperatures to foraging: 2. Colony management. Beekeepers can speed up • 55–60°F—some foraging or slow down the natural growth of their hives • 60–65°F—moderate to fair amount of foraging with a variety of techniques. • 65–70°F and above—maximum amount of • Colonies given supplemental food (such as foraging sugar syrup) and/or pollen supplement early in During midsummer, the same colonies often the season are stimulated to grow more rapidly. will not start foraging until the temperature reaches • Colonies taken to California in December or 70°F. The bees’ “acceptable foraging temperature” January (primarily for almond pollination) apparently shifts with colony requirements and begin foraging earlier. Later on, they may be the season. Colonies receiving morning sun in the stronger than colonies that overwintered in the 2 Archival copy. For current version, see: https://catalog.extension.oregonstate.edu/pnw623 Pacific Northwest. When the beekeeper brings Colony-strength regulations these colonies back to the PNW area, they are Oregon and Washington departments of in better condition for early season pollination agriculture, in 1960 and 1978 respectively, mandated service. colony-strength regulations for hives involved • When beekeepers consider colonies to be overly in commercial pollination of agricultural crops. strong early in the year, they often split them The regulations were designed to assure growers into several colonies, adding new queens to the that colonies they rent meet minimum biological new colonies. Most beekeepers use this method standards. Currently, these regulations are not being to increase their total number of colonies. enforced, but the standards set forth can still serve as minimum colony-strength requirements and help How many to use? identify colony quality. Consider these regulations Perhaps the most important question the as recommendations and use them to define commercial grower asks is: How many colonies are colonies in pollination contracts. necessary to ensure maximum pollination of a given The Oregon and Washington regulations set crop? This is a difficult question to answer. forth several years ago appear on pages 7–8. Note • Absolute pollination requirements are not that while there are two grades (A and B), there established for most agriculturally important are also two grade types, Field and Orchard. This plant species. recognizes the natural growth pattern of a honey • Bloom periods, bloom density, bloom bee colony. Colonies rented for tree fruit pollination attractiveness, blossom structure, competing early in the season will not be as strong as the same bloom, and weather determine how well honey colonies rented later in the year for field or row crop bees will forage on and pollinate a given crop. pollination. • The number of hives to use depends on the quality The colony grades, as defined by the regulations, of individual colonies. can be more easily understood with a few explanations. The average numbers of hives employed per acre for pollination in some important crops in the Disease Pacific Northwest and for almonds in California are Two bacterial infections are significant for listed in Table 1. beekeepers, and it takes an experienced beekeeper to tell them apart. American foulbrood is the most Table 1 . Average number of hives needed for serious bee disease in North America. It simply pollination in the Pacific Northwest (per acre) . means the death of the infected colony—it can’t be Crop Number of hives tolerated at any time. European foulbrood can be Almond (in California) 2.5 tolerated at low levels of infection, especially early in Apples 1.5 the season.