Pollination and Bee Poisoning Prevention

Table of Contents

1. Pollination Requirements for Fruit Crops
2. Using Honeybees Effectively
3. Recommended Publications
4. Bee Poisoning

Pollination Requirements for Fruit Crops

Most fruit crops benefit from or require insect pollination.

Apples

Apple cultivars grown in Ontario do not generally set fruit with their own pollen. Pollination with pollen from more than 1 cultivar normally results in larger fruit compared to fruit grown from a single source of pollen. A bloom requires 8–24 visits by pollinators. A well-designed orchard reduces the number of bee visits required. Good pollen movement is necessary for fruit with high seed count. Good pollen movement in a higher density planting is generally limited to 3–4 rows across the orchard. The distance pollen travels down the row is limited to a few trees. For this reason, 2 or more compatible cultivars must be planted together in the orchard to allow for cross-pollination and fruitfulness. Varying the placement of beehives does not normally have a significant influence on pollen dispersal distances within the apple orchard.

Apricots

Most varieties are self-fruitful and may be planted in solid blocks. Because apricots bloom early when the weather is unreliable, provide honeybees to help with pollen transfer.

Blueberries

Blueberries are self-fruitful and may be planted in solid blocks. However, cross-pollination of cultivated blueberries can give larger berries, higher yields and somewhat earlier ripening. It is advisable to plant more than 1 blueberry variety. Honeybees help with pollination.

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Sour Cherries

Sour cherries are self-fruitful and do not require pollenizer cultivars for a commercial crop. For maximum production of sour cherries, use honeybees at a rate of 2 strong hives per hectare. Sour cherries and sweet cherries are different species, and will not pollinate each other.

Sweet Cherries

Sweet cherries are not pollinated by wind; the honeybee — use 2 hives per hectare — is the only effective pollinating insect reported. Many sweet cherry cultivars are self-unfruitful and must not be planted in solid blocks. Certain groups of cultivars will not pollinate each other. Careful attention to planting arrangement of sweet cherries is required. Recent sweet cherry cultivar introductions from the Vineland breeding program are self-compatible.

Currants and Gooseberries

These are self-fruitful, but insects assist in pollen transfer. Honeybees can increase crop yield.

Grapes

All commercial varieties of grapes are self-fruitful and are pollinated by wind. It is not necessary to provide honeybees for pollination.

Peaches and Nectarines

All commercial varieties grown in Ontario are self-fruitful and may be planted in solid blocks. Honeybees readily work peach blossoms and frequently cause a heavy set, resulting in extra thinning costs. For this reason, do not put beehives in peach orchards.

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Pears

All varieties in Ontario are self-unfruitful. Mixed plantings are necessary. Insects are required for cross-pollination. Honeybees do not find pear blossoms as attractive as most other fruit. Careful timing of the introduction of honeybees to orchards is necessary. Place up to 8 strong hives per hectare when the orchard is about 25% in bloom. Use pollen inserts to help overcome pollination problems.

Plums

Consider both European and Japanese plums as self- unfruitful. Mixed plantings and insect pollinators are essential. Honeybees readily work plum blossoms.

Raspberries and Blackberries

Raspberries are self-fruitful. Their bloom is very attractive to bees.

Strawberries

Strawberries are self-fruitful, and are pollinated by gravity, wind and insect transfer. Pollination by honeybees or other insect pollinators may improve berry size and shape.

Tree Nut Crops

These rely on cross pollination achieved mainly by wind action.

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Using Honeybees Effectively

The primary domesticated insect pollinator of cultivated crops is the honeybee. Many growers facilitate the pollination process by arranging to have beekeepers move honeybee colonies into their crops during the blooming period. The following information will help you use honeybees more efficiently.

• Obtain honeybees from a reliable beekeeper able to supply strong, healthy colonies. Weak colonies are of little value for early spring pollination when cool weather is often encountered.

• Two to 3 colonies of honeybees per hectare provide satisfactory pollination. Stocking rates vary depending on the type of fruit, the variety and the planting density. In young orchards fewer honeybee colonies may be required because there are generally fewer blossoms to pollinate. On the other hand, for early blooming fruit crops such as apricots, cherries and plums, you are better off to use more honeybee colonies than the recommended stocking rates indicate. This precaution should compensate for the negative effect of cold weather, which often occurs during the pollination period of these crops.

• A pollen insert is a device that forces bees leaving the hive to crawl through a shallow tray containing pollen from the desired pollenizer. Pollen adheres to the legs and body of each foraging bee to enable it to cross-pollinate the blossoms it visits.

• When using a pollen insert, place hives in the crop after blossoms have partially opened (earlier for sweet cherries, later for pears). This encourages more bees to work the fruit blossoms in the immediate surroundings, rather than foraging elsewhere. This recommendation is extremely important to ensure the effective use of pollen inserts. Have 5 colonies per hectare when using pollen inserts.

• Weather is often cool during the pollination period for early-blooming fruit crops. To encourage maximum honeybee flight during cool weather, protect the colonies from cold spring winds. Place the colonies in larger groupings in sunny, sheltered locations. Where there is no natural windbreak, erect a temporary wind shelter using, for example, bales of straw. Place the colonies so that the morning sunshine strikes the hive entrances.

• Provide water to colonies during bloom periods that are exceptionally dry. Bees will abandon pollen collection in favour of securing water for the colony. A shallow tub of water with floating sticks allows bees to land without drowning.

• Honeybees favour apple pollen over dandelion pollen. Apple pollen provides a higher quality protein that bees require to feed colony brood. Although bees will forage on dandelion as a protein source, the vast majority will move to apple pollen quickly when it becomes available. Apple growers do not need to be concerned about dandelion bloom drawing bees away from apple bloom. A rigorous program of mowing dandelion bloom in orchards is no longer recommended for Ontario apple growers.

• For information contact the OMAFRA apiary specialist at 1-888-466-2372 ext. 63595 or by e-mail at doug.mcrory@ontario.ca.

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Recommended Publications

For more information on pollination requirements of fruit crops, refer to OMAF Publication 430, Fruit Cultivars, A Guide for Commercial Growers.

Bee Poisoning

Bees are essential for the pollination of most tree and small fruits. Insecticides, many of which kill bees, are required for insect control. With careful management, you can obtain both pollination and insect control. You can protect the bees by following these suggestions.

• Do not apply insecticides while fruit trees are in bloom. The Bees Act makes it an offense to do so in Ontario. Read label for guidelines.

• Time of treatment is important. In general, daytime treatments when bees are foraging in the field are most hazardous. Insecticide applications in the evening are the safest. Early morning is the next best time.

• Remove honeybee colonies as soon as pollination is complete and before any postbloom insecticides are applied.

• If there is a risk of honeybee poisoning, try to choose an insecticide that is not highly toxic to the bees.

• Honeybees frequently are poisoned by visiting cover crops, such as dandelions or clovers, that are in bloom in the orchard. Clipping or beating down such crops prior to spraying will help safeguard the bees.

The following groups found in Table 6–1, Relative Toxicity of Pesticides to Honeybees, (chemicals used with fruit crops) show the relative toxicity of pesticides to honeybees as determined by laboratory and field tests.

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Extremely Toxic to Bees

FURADAN 480F

This insecticide has caused more loss (confirmed cases of poisoning) to bees in Ontario than any other of the materials mentioned in this publication. Fruit growers and apiarists require close liaison when and where Furadan is used.

For more detailed information on the toxicity of specific pesticides to honeybees refer to the pesticide label.

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