Many fruit trees are starting to bloom in Ontario orchards, so it is a good time to re-visit some information about pollination in orchards. Honey bees, native bee species (e.g., bumble bees, squash bees) and other pollinating insects are important pollinators for many Ontario crops.
Table of Contents
Tips for using honeybees effectively
- 2 to 4 (healthy) colonies of honeybees per hectare generally provide satisfactory pollination.
- Bees must be placed in the orchard at the appropriate time. Wait until 30% of the blooms have opened in plums, and in pears, 10%-20% of blooms open.
- Provide an adequate number of pollinizer trees. There should be at least one tree of a pollenizer cultivar for every eight trees of the main cultivar (pears), and plant every fourth tree location and every fourth row for cherries.
- Protect beehives from cold spring winds. Place the colonies is larger groupings in sunny, shelter locations. If a natural windbreak is not available, erect a temporary one ( eg. a wall of straw bales or orchard bins).
- Situate the colonies so that the morning sun warms the entrance.
- Provide fresh water especially if the bloom season is dry. Floating sticks in a shallow tub will allow bees to land without drowning.
- Watch for open water that is contaminated eg. puddles near your sprayer loading area.
- Since pear and plum blossoms are less attractive to bees than dandelion flowers and other weeds (which contain more sugar nectar), be sure to mow the orchard during the pollination period. This is less important in apples, which are more attractive to bees.
Bee poisoning Taken from Using Pesticides in Ontario (gov.on.ca)
Insecticides, some of which may negatively affect bees, require careful management to achieve both pollination and insect control of pest species. Growers and licensed commercial applicators can protect bees by following these suggestions:
- Time insecticide applications to minimize bee exposure (e.g., apply post bloom). Daytime treatments, when bees are foraging, are most hazardous. Insecticide applications in the evening are the safest, unless there is evidence of a strong temperature inversion or high humidity. Under normal circumstances, spraying after 8 p.m. allows the spray to dry before the bees are exposed to it the next day. Spraying during early morning is the next best time, when fewer bees are foraging, but pesticide residues may still be present. Spraying should be completed well before 7 a.m. While honey bees and most other pollinating insects do not usually forage at temperatures below 13°C, bumblebees do. If you plan to spray in the morning, contact beekeepers who have bees within 5 km of your crop and spray site. The beekeepers may then have the option of taking any possible protective action.
- Do not apply insecticides while fruit trees are in bloom. The Bees Act makes it an offence to do so in Ontario. Do not spray any flowering crop on which bees are foraging.
- To prevent drift toward nearby hives, do not apply insecticides on windy days or when there is evidence of a strong temperature inversion.
- Bees and other pollinators may be poisoned by visiting flowering weeds, trees and cover crops that have come into contact with an insecticide via spray drift or drift of insecticide-contaminated dust during planting. Avoid spray drift to flowering weeds that are adjacent to or within the target field. Where possible, mow down flowering cover crops or flowering weeds in and bordering target fields prior to spraying to help safeguard the bees. Control dandelions and other flowering weeds within fields before spraying or planting seeds treated with an insecticide. Take measures to reduce movement of dust from insecticide seed treatments to flowering trees, weeds and water sources that are in or adjacent to the target field. For more information on reducing dust movement, search for “Pollinator Protection and Responsible Use of Treated Seed — Best Management Practices” at www.canada.ca.
- Systemic insecticides may also pose a high risk to bees and other insect pollinators. Bees can be exposed to insecticide residues in or on flowers, leaves, pollen, nectar and/or surface water. Do not apply insecticide or allow it to drift onto blooming crops or off-site habitat if bees are foraging in or adjacent to the treatment area.
- In crop settings where pesticide use is highly likely, beekeepers should remove honey bee colonies as soon as pollination and bloom are complete in the crop and before any insecticides are applied post bloom. In emergency situations, if the colonies cannot be removed in time, beekeepers can place burlap or cloth soaked in water at the entrance of the hive to disrupt the flight of the bees for up to 12 hr and provide more time for spray to dry. To help prevent overheating of the hive during this time, keep an opening of 2.5 cm on each side of the hive entrance so bees can still get out and ventilate the hive. Also, the water on the burlap or cloth will help cool the colony.
- Not all pesticides are equally toxic to bees. If there is a risk of honeybee poisoning, try to choose an insecticide that is not highly toxic to bees. When there is a choice, choose a product formulation that is less hazardous to bees.• Always read the most current pesticide label for guidance. Some pesticides cannot be used when bees are active in the crop.
Encouraging bee diversity
By encouraging wild bee diversity on their farms, growers may see benefits to orchard pollination. Some research suggests that orchards visited by many kinds of bees have higher fruit set than those visited by one type of bee. Native pollinators may be active in cooler conditions then honeybees, helping to increase pollination in cool wet springs.
Pollination requirements for commercial crops
In general, the percentage of blossoms available at bloom that need to be set by pollination to provide a commercial crop are as follows: apple 2-8%, apricot 20-25%; pear 3-11%; peach 15-20%; and cherry 20-75%.
Conclusion
Bee communities, both wild and managed have an important role in pollination, and in our ecosystem. It is important to protect bees and their habitats.
For additional information about pollination in orchards see:
Wild bees in apple orchards | ontario.caThe Profits of Protecting Pollinators – ONfruit