Where have all the Honey Bees Gone?

By: Lucas Duralia


Every year, Insects alone pollinate billions of dollars worth of crops worldwide. By far the most domesticated of these crop pollinators is the honey bee (Apis mellifera L.). Although originally managed only for its honey and wax, the honey bee has become a highly successful pollinator under years of conventional crop production.


Due to the migration of Africanized (killer) bees and the recent threats to honey bees from parasitic mites, producers growing crops which rely on pollination from honey bees are facing major challenges. As pollination costs continue to rise and honey bee populations continue to drop, the need for alternative sources of crop pollination has become apparent.


Traditionally, advocates of pollinating bees have been separated between those for honey bees and those for non-honey bees. While there has always been strong competition for funding between these two groups, the majority of funding has landed on the honey bee side. As a result, only a handful of the 30,000 non-honey bees found worldwide have received enough serious attention and adequate funding to be developed into domestic crop pollinators. The alkali bee (Nomia melanderi Cockerell) and the alfalfa leafcutting bee (Megachile rotundata Fabricius) are among the top of the Pacific Northwest list. Because they are highly adapted to the hot, dry alfalfa seed growing climates of eastern Oregon, eastern Washington, and Idaho, these wild bees are far more efficient than honey bee at pollinating alfalfa. On the other hand, these wild bees exhibit a limited forage crop preference and are not adapted to the western climates north of Medford, Oregon.


Next to the alkali and alfalfa leafcutting bees, the mason bee species of the genus Osmia have without a doubt undergone more scrutiny than any other wild bee crop or orchard pollinator. Among these bees is the orchard mason bee (Osmia lignaria propinqua Cresson) and is found in wooded areas near homes throughout western Oregon and Washington. With their ability to forage on a wide variety of pollen and nectar plants, orchard mason bees are often observed visiting early season fruit tree blossoms. They are commonly recognized for their efficient pollination capabilities and their ability to forage in poor weather conditions. Surprisingly, they are often seen flying and foraging in conditions 3 - 4F cooler and wetter than honey bees. The orchard mason bee has proven to be an effective pollinator in apple, plum, and almond orchards.




The greatest surprise about the orchard mason bee is how few people know about it. The orchard mason bee is a gentle and beneficial pollinator of tree fruits, with a sting that is no worse than a mosquito bite. They are not aggressive and will only sting if threatened, usually when handled roughly or trapped under clothing. It is the ideal pollinator for urban areas and should be encouraged to nest in nearby areas. They make their nests in reeds and natural holes. Unlike carpenter bees, they cannot drill holes into wood themselves which often leads them to investigate small crevices such as nail holes or even gaps under siding. Although homeowners are often concerned when they see orchard mason bees entering small spaces such as these, they are not destructive insects and no controls are necessary. Because they cannot excavate the holes themselves, they simply use preexisting holes for non destructive nesting.


Orchard mason bees differ from honey bees in a variety of ways. Not only do they not produce honey, but they also have a shorter flight range and a completely different appearance than the honey bee. Orchard mason bees generally do not travel much further than your garden with their flight range of about 100 yards. Honey bees on the other hand have a flight range of a mile or so. When comparing appearance, the orchard mason bee is slightly smaller in size than the common honey bee. Additionally, their looks differ from the honey bee with their shiny dark blue color. Male and female orchard mason bees can also bee differentiated through their appearance. Males are smaller than females, have slightly longer antennae, and have additional light colored hairs on the face. Females have additional hairs under the abdomen, an adaptation for carrying pollen.


Nesting Habits


When the female searches for existing holes in wood for her nest, she chooses holes slightly larger than her body, usually 1/4 to 3/8 of an inch wide. The first thing she does is place a mud plug at the bottom of a chosen hole. She then collects nectar and pollen from spring flowers and brings somewhere between 15 and 20 loads into the hole. If watched closely while entering her nest, one can actually see the pollen on the underside of her abdomen.

After filling a cell with a sufficient food supply for her larva, she then lays an egg and seals the cell with a thin mud plug. She then creates another cell, and continues until the hole is full. Finally, she plasters a thick mud plug at the entrance of the nest. While some wasps also build nests in such holes, their nests can be distinguished from the orchard mason be nests by the look and feel of the plug. While the wasp prepares a smooth plug, the orchard mason bee prepares a plug that is rough.


Although the female orchard mason bee only lives for about a month, she can produce up to two eggs a day. After a few days, the larva hatches from the egg and begins to eat the prepared pollen and nectar mass. After about 10 days when the food is gone, the larva spins itself a cocoon and pupates with the cell.


The bee makes its transformation to the adult stage near the end of summer, but remains in the cocoon throughout the winter. When the weather has warmed in the springtime to a daytime temperature of about 14C (57F), the males emerge by chewing their way out of the cocoon and through the mud plug. The females, which are usually in the tunnels inner cells, tend to emerge a few days after the males. During cooler weather, it can take up to two weeks for all the bees to emerge.


Females mate soon after their emergence and begin nesting after 3 or 4 days. The bees forage on a variety of different flowers including apples, cherries, Oregon grape, and dandelions.


How to Build a Bee Condo


Trap nests are commonly set out in order to increase bee populations for the purpose of pollinating a home or even a commercial orchard. Trap nests are made by drilling small holes anywhere from 1/4 3/8 inches in diameter and about 3 inches deep into 4x4s. They are ideally attached to the side of a house or shed where there is some protection from rain, but can also be placed on trees or posts in wooded areas. The bees main requirements include a good supply of mud for constructing nests and flowers on which to forage. If a natural mud source is not readily available near the nests, we recommend digging a shallow hole, lining it with a plastic, and finally filling it with moist soil.

Trap nests should be somewhat strategically positioned where they will receive morning sunlight. They should be put up in March before the bees begin to build nests. If they are left out through the winter, preferably under cover to protect them from the weather, the bees will begin to emerge in April. The bees will begin to forage for pollen when apples bloom and continue afterwards as long as there is a sufficient supply of other flowers available to them as well.


If planning to develop large populations for orchard pollination, it helps to store the nests in a refrigerator at 35 to 40F. This not only allows one to control their emergence time, but also protects the nests against predators and parasites. The nests should not be placed into storage until September or October in order to assure the adults develop completely. When spring arrives, the nests should be placed among the fruit trees facing east. They should be placed a few days before the fruit trees begin to bloom. If necessary, one can induce emergence by incubating the bees at room temperature for 24 hours before placing them in the orchard.


Ideally, one should provide 500-1000 filled holes per acre. Assuming an average of 1 females per hole, 750-1500 females per acre is expected. While males also visit flowers, they do not have a long lifespan and are not nearly as effective when it comes to pollinating an orchard. When fruit bloom begins, it is recommended that any competing flowers are removed in order to encourage pollination of the specific orchard.


Because the short duration of bloom limits reproduction, the development of a large population of bees may take some time. However, it is not uncommon to develop a relatively large population of bees in 2 or 3 years.


Protecting your Mason Bees


In order to protect your population of orchard mason bees, it is important to know of the different dangers they face. The first danger is ichneumon flies, which feed on the bees. Birds have also been known to become a problem. Birds can be held at bay by protecting nests with a screen of inch mesh hardware cloth. Parasitic wasps have also been known to enter nesting tubes from the back. Preventing their backdoor entrance is as easy as backing the nests up against a wall. Finally, it is important not to spray insecticides in the garden from March through June. After June, spraying should not be much of a problem because the eggs are sealed with a protective layer of mud.