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Managing Colonies for Crop Pollination

By GORDON D. WALLER
Entomologist, Science and Education Administration, Carl Hayden Center for Bee Research, Tucson, Ariz. 85719.

BEEKEEPING IN THE UNITED STATES
AGRICULTURE HANDBOOK NUMBER 335
Revised October 1980
Pages 73 – 77

For centuries honey bee colonies were managed primarily for honey production. Crop pollination occurred as a side benefit to the grower. When fields increased in size and pollination by native pollinators and resident colonies became insufficient, the practice of renting honey bee colonies for crop pollination became commonplace. Today, thousands of colonies are rented by growers of various crops that require insect pollination.

When colonies are used for crop pollination, their value to the grower who rents the bees is measured in fruit or seed produced, not by the honey and wax produced. For the greatest value to the grower the bees must be managed somewhat differently than for honey production. The purpose of this chapter is to present the best information available on managing bees for crop pollination.

Selecting Proper Equipment

Hives

Hives that are to be subjected to frequent moves should be in good condition and of uniform size to facilitate loading and tying down. Telescoping outer covers and bottom boards with landing platforms projecting more than 2 inches prevents the hives from being stacked close together.

Vehicles

Trucks and trailers used to move bees should have smooth flatbeds with hooks around the edges to which ropes can be tied. Pickup trucks and trucks with stake beds make loading and tying down somewhat difficult.

Many beekeepers equip their trucks with a mechanical loader or keep their colonies on pallets and use forklifts for loading to reduce the amount of handlifting. Others use hand trucks (sometimes motorized) and either a ramp or a power-lift tailgate.

Making an Agreement

Contracts

Both the grower and the beekeeper should know precisely what their responsibilities are in relation to the pollination service. A well-understood written agreement should be signed by both parties before the bees are moved to pollinate the crop. The agreement might include the following information: identification of participants, number of colonies, colony strength, rental price, date of delivery to the crop, location or placement of colonies, duration of stay, provisions for water, protection from pesticides, access by the beekeeper, date of removal from the crop, and method of payment, penalties, and rewards.(2)

(2) For more information on this subject, see “Pollination Agreements and Services in U.S. Department of Agriculture, Agriculture Handbook No. 496, “Insect Pollination of Cultivated Crop Plants” by S. E. McGregor, or chapter 20, “The Use of Bees for Crop Pollination,” in The Hive and the Honey Bee, Dadant & Sons, Inc. Hamilton, Ill. 1975.

Colony Evaluation

When a poor set of seed or fruit is attributed to poor pollination, the blame often is put on the beekeeper. Beekeepers cannot guarantee that their bees will work the target crop, but they can guarantee a certain minimum standard colony.

Shortly after the bees have been delivered, the beekeeper and grower should examine a random lot of the colonies to ascertain their quality. Most farmers are not experts in evaluating bee colonies, but they can determine that most of the hive bodies have frames of drawn comb covered with bees, which is better than no information. They also might enlist the aid of a third party who can assess colony strength in terms of number of frames covered with bees or number of frames of brood. The grower should not pay for colonies that are queenless, diseased, or below a minimum population level.

Adequacy of Pollination

Few guidelines exist that describe adequate bee activity for specific crops. For some crops, the pollination needs have been expressed in terms of bees per 100 flowers, bees per square yard, or bees per 100 feet of row. Unfortunately, few farmers take the time to determine the bee visitation with such precision. Even if they did, the variables of time of day and weather conditions might make such counts somewhat undependable. Recommendations usually vary from one-half to five colonies per acre, but the real criterion is how many bees are working the crop, rather than visiting other attractive plants in the area.

With some crops, such as alfalfa, experienced individuals can assess effectiveness of pollination by the general appearance of the crop (fig. 1). Soon after alfalfa flowers are tripped and pollinated, the petals wilt. When the flowers are not tripped, they remain fresh and the field takes on a showy “flower garden” appearance that contrasts with the dull brownish appearance of a field that has been well pollinated. Examination of individual florets on several racemes also will reveal the percentage of tripped flowers.

FIGURE 1.-Colonies in alfalfa in the West.

Unfortunately, flowers of many seed crops do not change noticeably following pollination. Only when the crop matures and harvesttime nears can the grower readily judge adequacy of pollination. This is too late to permit remedial changes in pollination to increase the yield. What is needed is a simple, inexpensive field technique by which the plants can be examined periodically to determine if they are being adequately pollinated.

Preparing the Colonies

Stock

Colonies intended for pollination rentals should be headed by young queens of gentle stock to reduce colony failures and to minimize the likelihood of people being stung.

Colony Population

The key to management of colonies for pollination is population control through proper timing of colony development. A colony with a small population sends forth few foragers. A high percentage of the bees in such a colony must remain in the hive to care for the brood and provide temperature and humidity control. With large populations, a greater proportion of the bees is likely to be involved in collection of nectar and pollen. Since pollination is the result of foraging activity, the colonies should be managed to provide a large number of foraging bees. When beekeepers manage bees primarily for honey production, highly populous colonies (60,000 workers) serve their purpose best. Such large colonies can be extremely difficult to move if four or five stories are required to contain them. Colonies rented for crop pollination are easier to manage if the populations are equal and the hive size is standardized. If the colony has a young queen and adequate comb space for brood and incoming nectar and pollen, it should require a minimum of attention.

To provide adequate colonies in early spring for fruit pollination, the beekeeper must begin preparations the previous fall. Only colonies going into winter with large populations of workers, a young queen, and adequate stores of honey and pollen will be dependable for early spring pollination activity. Conversely, late spring and summer crops, such as cucumbers or alfalfa seed, may require that colonies be divided or otherwise reduced in strength in the spring to prevent them from becoming overcrowded or subject to excessive swarming, or both. A swarm leaves only a remnant of the worker population in the parent hive, which seriously impairs the pollination effectiveness of a colony.

Reserves of Food

Colonies to be moved to a new area for pollination purposes should have ample honey stores. Sometimes, two frames of honey per colony are adequate. At other times, nectar is likely to be scarce and considerably more may be needed. Whatever the amount needed, the beekeeper should see that it is present.

Selecting the New Location

When possible, the beekeeper and farmer should visit the field together during daylight hours to select locations for the placement of colonies. Even when locations are selected in daylight, they often are difficult to recognize at night.

Proximity to the Crop

Farmers who intend to rent bees to pollinate small fields should plan locations that can accommodate groups of colonies nearby. If colonies are to be dispersed throughout larger fields, the distribution, location, and accessibility of colonies should be taken into account. Honey bees can travel several miles to forage, but the likelihood of their visiting a certain crop is decreased as the distance to the crop is increased.

FIGURE 2.-Palletized colonies placed in groups around the edge of alfalfa seed field for pollination.

The preferred distribution is to place the colonies in 2 or more groups around the edges of fields less than 20 acres and to distribute them in groups of 6 to 12 about 0.1-mile apart both around and within larger fields (fig. 2).

Where bloom on other plants is likely to attract foragers away from the target crop, the colonies might be placed on the opposite side of the field from the competition. Neither wind direction nor the direction the entrances face has any effect on where bees will forage-they tend to distribute themselves more or less uniformly in all directions from their hives, if the forage is similar.

Accessibility and Convenience

Proper management requires easy access to the locations to facilitate examination of the colonies, removing honey, or providing additional room for colony expansion. Roadways should be wide enough and turning areas adequate to accommodate the beekeeper’s vehicles.

Shade and Water

A nearby source of water is essential for the well-being of a honey bee colony. When water is not available naturally, either the farmer or the beekeeper should provide a temporary source of water for the duration of the pollination job. Large numbers of bees collecting water from stock tanks or around homes may create problems and should be avoided.

Colonies exposed to full sunlight during hot weather expend much energy carrying water to cool their hives. Placing colonies in the shade of trees, under temporary shades, or at least on or near some vegetation increases their efficiency as pollinators.

Protecting the Colonies

One reason beekeepers are hesistant to enter into pollination contracts is the danger of bee kill from pesticides. Even if the crop to be pollinated is not treated with pesticides, nearby crops may be treated and a loss may occur.

If beekeepers are notified a couple of days prior to the time of application of a pesticide, they may be able to protect their colonies by moving them away temporarily or by confining the bees in the hive. Of course, this increases the cost of providing the pollination service.

Consideration also should be given to the likelihood of losses due to vandalism. Colonies placed within full view of an occupied house, and/or located so entry to the area requires passing through a farmyard, are less attractive to vandals than colonies more easily accessible. The likelihood of floods, fires, and wind damage also should be considered when selecting a location.

Colonies placed along busy roadways may have a considerable number of bees killed by passing vehicles. Further, bees entering vehicles are a hazard to motorists. Heavily traveled, unpaved roads create a dust problem for colonies placed nearby-reducing brood viability and colony productivity. For these reasons, when practical, the bees should not be placed adjacent to roads or highways.

Moving Colonies

Timing

The timing of the move to coincide with initiation of bloom on the target crop may be quite important. If moved too early, the bees may forage among other plants and fail to shift to the target crop. If moved too late, the crop yield may be reduced by inadequate pollination of the early flowers. Contact between grower and beekeeper should be established several weeks before the bees are needed. Keep informed on the stage of flowering of the crop so the bees can be provided when needed.

Loading

Most beekeepers prefer to load their colonies into the vehicle in the evening just before dark. At this time, most of the foragers are inside the hive. In the southwest, where daytime temperatures exceed 100°F, flight activity during mid-day is greatly reduced. When colonies are moved at this time, few foragers are lost. Sometimes a weak colony is left behind for stragglers that may be salvaged later.

Confining the Bees

Bees can be kept inside their hives by screening the entrance. Sometimes a screen is placed over the top after the cover has been removed. Closing the entrance in a way that does not allow air circulation might kill the colony, because excessive buildup of heat and carbon dioxide can be lethal. An alternate method of confining the bees is to cover the entire load with a bee-tight plastic or nylon screen. Beekeepers sometimes move colonies with entrances open, if the colonies are to be unloaded before dawn and no stops by the vehicle are contemplated. Beekeepers should make sure that no problems are caused by escaping bees, or bothersome regulations are likely to develop.

The Move

Whenever possible, bees should be moved to their new location immediately after being loaded. In hot weather or on long hauls, spraying the bees with water helps to cool them and prevents dehydration. Immature brood (eggs and larvae) can suffer serious damage from excessively hot and dry conditions. A supply of clean water, readily available at the end of the move, will lessen loss of brood and reduce the chances of the bees collecting water poisoned by earlier insecticide applications.

Managing the Colonies

Feeding

The need for supplemental food will depend on the weather, the crop to be pollinated, and whether other nectar and pollen sources are available to the bees during the pollination period. Colonies used on crops that produce little or no nectar should have adequate stores, as previously mentioned. If short of stores, they can be given sugar syrup or frames of honey. Feeding will have little effect on their nectar foraging activity, and it may help maintain a higher level of brood rearing that ultimately results in greater pollen collection.

Providing Adequate Space

Colonies need adequate room for storage of incoming nectar and pollen, for an expanding brood nest, and for the additional bees that emerge. When not provided adequate space and they become overcrowded, colonies cease foraging if no storage room is available.

Pollination in Cages and Greenhouses

Bees are sometimes used in confined situations such as greenhouses and field cages. The amount of forage available in a cage or greenhouse will not support the bees of a colony, so they should be replaced periodically. If colonies are not provided pollen or pollen supplement, brood rearing soon ceases. If they are not provided with honey or sugar syrup, they will starve.

As a result of these problems, many beekeepers look upon colonies used to pollinate in confined areas as expendable. Some queenless units are provided with no hope for a surviving colony. Small colonies properly managed can survive nicely while providing pollination to caged or greenhouse-grown crops. The question that needs to be answered is one of economics-what should the beekeeper charge, based on the time required to service the colony and on its value at the end of the pollination period?