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Maintaining honey bees for crop pollination

May 30, 2002

It is the responsibility of the beekeeper to deliver strong, healthy colonies to the seed producer.

A strong colony should have between 600 to 1,200 square inches of brood, developing honey bee larvae and pupae. Counting the frames and multiplying by 100 can estimate square inches within frames.

Strong colonies have bees thickly massed over all frames, overflowing when the hives are opened, and dozens of bees should be seen flying about the entrance to the hive. If the hive is too strong, the bees may swarm leaving only about half of the bees in the hive without a queen.

An experienced beekeeper or an inspector from the county Agricultural Commissioner's Office can easily estimate the strength and health of a honey bee colony and identify any disease or mite problems that might exist.


All honey bee colonies should be registered with the county in which they are used; registration helps protect both the seed producer and the beekeeper.

It is better to have a few strong bee hives in a field than several weak hives. In weak hives, few bees are available to forage as most must attend to keeping the hive cool and to raising the brood. Strong bee hives have many bees that are available for foraging, pollinating many flowers.

During the summer a colony will lose many bees. Foraging workers are short-lived. Pesticides are the greatest hazard to foraging honey bees. It is important to have a strong brood population with larvae and pupae in all stages of development. It also is important to have a good queen to maintain a colony and to keep it from becoming weak.

To maximize the amount of seed produced in a field:

· start with good agronomic practices;

· cooperate closely with a good, reliable beekeeper;

· provide shade and water to maintain strong colonies and protect bees from insecticide applications;

· remove bees as soon as possible after seed set;

· always use pesticides safely and wisely to ensure the future of seed production by protecting honeybees.

The Pentagon is looking for new ways to fight terrorism, including the use of honey bees to locate explosives. Honey bees are being trained to discover minute traces of explosives and guide humans to the site at a fraction of the cost of more conventional weapons detections programs.

The idea of putting bees to work for mankind is not new and is not without its problems. Humans have been using bees for a source of honey, wax and for crop pollination since biblical times. A couple of the biggest problems for beekeepers maintaining colonies in North America today are the attacks of two small terrorists, the varroa mite and the tracheal mite.

The varroa mite, Varroa jacobsoni, is an external parasite of honey bees that attacks adult bees and their developing brood. An attack of varroa mite will cause a general weakening of the entire colony by decreasing brood. Varroa mites are quickly spread to bee colonies by traveling with swarms or migrating drones and by the movement of infested equipment.

Varroa mites are a serious threat to the U.S. honeybee industry, greatly reducing honey production. They also are a threat to agriculture in general as many crops depend on bees for pollination each year.

Female varroa mites lay up to 12 eggs in a bee brood cell. The mite nymphs feed on immature bees. When the mites are mature, females are fertilized and the males die. After mating, female mites attach themselves to adult bees to feed.

The female mites eventually migrate to bee larvae in brood cells that are about to be sealed. Older female mites continually feed on adult bees and lay eggs in brood cells.

The mites are about one-fourth the size of a rice grain and dark red-brown in color. Female mites can live for about two months during the summer but many can live for up to eight months during the winter, surviving with clustered bees.

Varroa mite-infected bee colonies may not show evidence weakness during the early stages of infestation, but parasitized colonies become weaker as the mites multiply. Young bees may have as many as 10 mites attached between the overlapping segments of the abdomen as a colony becomes heavily infested. Heavy infestations can be diagnosed by varroa mite feces on the insides of cells from which parasitized bees have emerged and dead bee larvae and pupae in various stages of decay can be found in combs. Also, mites can be detected on adult bees and on brood taken out of uncapped cells.

Another honey bee terror is the microscopic tracheal mite, Acarapis woodi. Bees infested with the tracheal mite can suffer severe losses; entire apiaries may die. Honey bee colonies are most likely to succumb to tracheal mites during a stressful overwintering period, regardless of honey stores. Like the varrora mite, tracheal mites cause severe economic losses for beekeepers by reducing honey production and pollination fees. A shortage of hives could adversely impact grower production or cause pollination rental fees to increase.

The tracheal mite lays its eggs in the honey bee breathing tubes called trachea. The entire life cycle of the mite takes place in the trachea of the honey bee. The mites feed on the body fluids inside of the trachea.

When the mite nymphal developmental cycle is completed, the adult mite emerges to seek another host bee. The new host is usually younger than 9 days old.

Tracheal mites can be numerous within a single bee. Tracheal mite feeding may damage flight muscles, but the actual process by which mites cause the death of a bee is uncertain.

>> Eric Natwick is an entomologist at the University of California-Imperial County Cooperative Extension.

>> The Cooperative Extension serves all residents of the Imperial Valley.

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