The use of honeybee hives for the pollination of wild blueberries is increasing. Occasionally, these hives are attacked by bears in their attempt to acquire brood and honey. Once the bears discover this food source, they return on a regular basis, especially at night. Protective measures should be in place before the hives are brought in to the field, so as to discourage the first attack from taking place. When protection is put in place after the first damage has occurred, it is rarely effective.

Beekeepers often use electric fences to ward off predators. Many wild blueberry growers in Quebec build protective enclosures for the hives by surrounding them with woven wire fences. When the hives are rented for pollination, the grower and the beekeeper need to determine who is to be responsible for installing the protective enclosure. The size of the area will, of course, be proportional to the quantity of hives which need protection.

ELECTRIC FENCE (Figure 1):

An electric fence is clearly the most effective means of protecting hives from attack by bears. Its effect is even more important psychologically than it is physically. At a touch, the bear gets a shock which needs to be sufficiently painful as to not be forgotten. To be effective, the fence needs to be well installed. A decent ground is very important. When shopping for an electric fencing system, the grower/keeper should ensure that it is adequate for deterring predators. These are the components of an electric fence:

• The energizer (charger). A wide variety of energizers are available for a number of uses. A battery powered energizer, with a 12-volt battery, is recommended for protecting beehives. Solar-powered energizers are also available, but their high price make them a less interesting alternative. When selecting a battery, it is important to check the unit's power, which is measured in joules. To deliver a sufficiently painful shock to deter a bear, the charger should supply 0.7 to 1.3 joules.

  The energizer and battery can be placed in an empty hive within the area enclosed by the fence in order to prevent vandalism or theft of these items.

• The ground. Under dry conditions, the soil is not a good conductor. Without a proper ground, the electrical unit is not effective and will not deliver a shock, even if the system is very strong. To remedy this, plant one or more 25 mm galvanized rods at 2 m intervals, to a depth of 1 metre, and connect them. Another way to improve the efficiency of the system under dry soil conditions is to install chicken wire 15 cm from the base of the fence and all the way around it. The chicken wire should not touch the electrical cords, but should be attached to one of the ground stakes near the fence.

• Electrified wires. The type of electrified wire used will depend on the type of fence. For a permanent fence, a high-tension metal wire is recommended. For a temporary fence, a thin high conductivity "polywire" is recommended. A polywire system is easy to install and use.

  To adequately protect the hives, a minimum of four wires should be installed at heights of 24, 50, 85 and 105 cm above the soil. The wires need to be connected in order to ensure that the current passes through all of them. To avoid having a bear put his head between the wires, use a lard "bacon" bait to entice him to touch the electrical wire with his snout or his tongue. This will result in a more painful and memorable shock.

• The posts. The corner posts should be well anchored to the ground while the others should be installed 4 m apart and will define the perimeter of the beehive area. These posts can be made of cedar, insultimber or metal. Insulators are necessary, except in the case of insulated posts like insultimber. The insulation stops a ground from being created by way of the posts.

• Electrified gate. The electrified gate consists of simple spring or thin polywire, attached to the end of a handle. The number of gate handles should be equivalent to the number of wires, that is at least four.

WOVEN WIRE FENCE (Figure 2):

Some growers prefer to use barrier fences which are not electrified. This decision is usually based on the cost of electric fencing and also on the number of apiaries which need protection. The woven wire fence is a permanent structure. It is not electrified and therefore needs to be extremely sturdy in order to prevent the bears from reaching the hives.

• Posts. Four-metre cedar posts, pounded to a depth of 1 m., and placed at 3 m intervals will define the perimeter of the beehive area. The corner posts should be well anchored to resist the tension of the woven wire. The base of the posts should be treated, to prolong the usefulness of the posts.

• Woven wire. Two series of woven wire (10 or 15 cm mesh), one laid over the other, can be used to cover the full height of the posts. The lower one is dug 25 cm into the soil. It is very important to secure these solidly.

• The gate. The gate allowing access to the interior of the enclosure should be solid. It can be framed by metal or wood. The interior of the frame can be covered with woven wire.

CONCLUSION

In order to avoid significant losses, it is important to maintain good communication between the grower and the beekeeper, regardless of the understanding with respect to hive protection. Since the grower is more frequently in the field, he should advise the beekeeper of any potential problem.

References: Caron, D. M. et al. 1992. Diseases and Pests of Honey Bees. In The Hive and the Honey Bee (Joe M. Graham, ed.) Dadant & Sons, Hamilton, Illinois. Pages 1083-1151. Gallagher Power Fencing Systems . Power Fencing, 7th edition. Vickery, V.R. 1991.The Honey Bee. A Guide for Beekeepers. Particle Press, Pincourt, Qué. 250pp

Prepared by: Bernard Savoie, P. Ag., Horticultural Technician; John Argall, P. Ag., Provincial Blueberry Specialist, N.B. Department of Agriculture & Rural Development. Figures provided by Gary Wheaton, Engineering Technologist, NBDARD

Winter 1996