Tree Fruit Leader, Vol. 4(1) Mar. 1995

Bees and Pollination

John Gates, Apiculture Specialist, BCMAFF, Vernon

Honey Bee Shortage?

By now, many orchardists have probably heard of the exotic honey bee mite Varroa jacobsoni. Varroa can decimate honey bee populations very rapidly as has been demonstrated throughout the US. In the last few years there have been reports of bee shortages for pollination in a number of states.

Last spring in the Fraser Valley, Varroa was partly responsible for the death of approximately 60% of the areas' honey bee colonies. As a result, Cranberry growers imported about 1400 hives from the interior for pollination, at greatly increased prices. There is some early indication that Varroa is beginning to take its toll in the Southern Interior, especially in areas close to the U.S. border. Hives around Osoyoos and Oliver should be the most vulnerable because Varroa has been established in that area for some time.

Whether you hire bees for pollination or not, Varroa will eventually impact your pollination. A lot of pollination activity is conducted by wild honey bee colonies and by bees from unmanaged "hobby" hives. Varroa will eliminate virtually all of those bees.

It is still too early to predict what the impact of the mite will be this coming season. It could be business as usual or there could be some problems. Growers and beekeepers should carefully monitor the situation. March and April will tell the tale. Growers should stay in contact with their bee suppliers and work out some arrangements for replacement hives if necessary.

The Orchard Mason Bee - A Potential Pollinator for Tree Fruits

Last spring Margriet Dogterom (Simon Fraser University) and I indicated a joint project to study a native, locally occurring species of solitary bee Osmia lignaria (Orchard Mason Bee). A number of wild bee species including several Osmia species have been identified in or around orchards and other horticultural crops in B.C. but have not been evaluated for commercial pollination in our conditions. Studies in Utah and California have demonstrated that Osmia lignaria is an efficient pollinator of apples, prunes and almonds and has potential for other crops. In Japan, a close relative, Osmia cornifrons is used extensively in apple pollination.

Osmia lignaria is active as a foraging adult in early-late spring. Females lay their eggs at this time and the new generation of bees undergoes development throughout the rest of the season, remaining in diapause throughout the winter months waiting for spring to arrive. In nature the females nest in tubular holes in wooden material and construct mud pugs to partition the tubes into separate nursery compartments. The ends of the tubes are also capped with a thick mud plug, hence the common name, Orchard mason bee. For management purposes, paper or plastic straws and wooden blocks are used for nesting materials. Its natural foraging period in the Okanagan should coincide with cherry and apple bloom, but it can be incubated to time its period of activity to many different crops. Lignaria is managed similarly to the alfalfa leafcutter bee which is now the pollinator of choice for alfalfa seed production.

We decided to work the lignaria because of potential honey bee shortages due to the two new parasitic honey bee mites, now established in B.C., which have caused so many problems in the U.S. Questions still need to be answered before lignaria can be used successfully for commercial pollination.

Although we could have obtained sufficient lignaria from the U.S. to initiate pollination trials here, we decided to try to collect local bees to avoid importing diseases or pests which our populations may not have. Margriet Dogterom put out about 1,000 nesting straws which were set out in each of twelve communities (Keremeos, Cawston, Oliver, Vaseaux Lake, Naramata, Summerland, Vernon, Enderby, Chase, Dawson Creek, Maple Ridge and Victoria). Approximately 3,400 Osmia cocoons were collected and are now in storage until spring. When the adults emerge we will be able to identify the Osmia species we have captured. The majority of the cocoons were gathered in Victoria and Enderby where 165 and 52 cocoons respectively were collected for every 100 straws set out. Collecting success was a lot lower in Vaseaux Lake, Cawston/Keremeos, Summerland and Chase (about 5 Osmia for every 100 straws). Vernon, Naramata and Oliver yielded less than two per hundred and no Osmia were found at the Dawson Creek sites.

Similar to honey bees and bumble bees, mites were found to be associated with our local Osmia. In Japan and China, mites are the major Osmia pests, thus mite control could become an integral part of Osmia management.

To date, funding for the project has come from Ministry of Agriculture, Fisheries and Food sources, Simon Fraser University and donations from private beekeepers. Unfortunately our funds will be exhausted soon so we are looking for new money. No funding has been secured from the tree fruit industry but other commodity groups are showing an interest, so pollination trials may be diverted to other crops at the coast. A proportion of the Osmia collected in 1994 will be returned to the capture sites.

For more information contact Margriet Dogterom in Vancouver at 936-5843 or John Gates in Vernon at 260-3000.

Beehive Distribution for Pollination

Years ago, the number of hives per acre required for proper tree fruit pollination were established based on old standard, wide spaced plantings. One to two hives per acre have remained the general recommended rate since that time. With the introduction of new planting styles and varieties the question of how many hives per acre is being revisited. There is one important point, though, that has been overlooked by many in the past when considering how many bees to use - not all honey bees remain in the orchards where their hives are placed.

Hive distribution studies in Canada and the U.S. have demonstrated that honey bees tend to distribute themselves fairly evenly over a large area. They adjust themselves to the available forage and to the level of competition. If there are a lot of bees in an area, some of them move to other areas where the forage is as good. So what does that mean for the orchardist?

Well, orchardists hiring bees at the recommended rate may not be getting maximum pollination if neighbouring growers do not bring in bees. The entire area will be pollinated to some extent, but at a lower level than the recommendations originally had intended. The point is, pollination should be considered on a "community basis . . . encouraging your neighbours to rent colonies of bees will help you also".

This point is discussed in the "Almond Pollination Handbook", the best practical guide to pollination for both growers and beekeepers that I have read. It is written in an easy to read style and its author obviously has considerable commercial experience in the area. Don't let the title put you off. The principles involved apply to almost any crop requiring pollination, especially tree fruits. It is written in two sections, one for growers and one for beekeepers and covers all the issues important to both groups, including orchard design for pollination, things to consider when renting bees, managing bees for pollination, when to remove bees, the basis for rental costs and other insect pollinators.

If you are interested in improving your knowledge of pollination, this is the book for you. Interestingly enough, the author suggests that this might be a nice gift for a beekeeper pollinator to give to an orchardist client.

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