Do's and Don'ts of Pollinator Care in Blueberry Fields

By Dan Woolley

This article initially appeared in the March 2015 issue of Atlantic Farm Focus, and is reproduced here with permission of the publisher and author.

A panel presented some Do’s and Don’ts about the care of pollinators at the Wild Blueberry Producers Association of Nova Scotia’s annual meeting.

Even with excellent pollination there are different things, like soil nutrition and water that will affect the ultimate crop, panel chair Dr. Chris Cutler told growers.

Without good pest control “you won’t get good productivity from pollination,” the Dalhousie Agricultural Campus research scientist observed. 

Even with a good bloom in a field the number of fruitlets on the plants will decline over time. “You can get up to a 70 per cent reduction in fruit formation by the end of the harvest season.”

Dr. Cutler noted plants generally produce more blossoms than fruit, and pest and disease pressures will vary from year to year. Once blossoms emerge the more bees that visit will affect fruit set for the better. “The number of clonal varieties you have in your field, the better will be the final fruit set. You need insects to vector pollen around and in the flower. Bees move pollen within flowers on a plant or between different plants. All these things will affect the amount of fruit you get.”

Some clonal varieties are also “self-incompatible” while others produce scarce pollen or have sterile anthers, or are cross incompatible, the scientist explained.

Some varieties only have a short flowering period or pollen receptability. He said 75 per cent fruit set may not be possible, while 70 per cent would be excellent.

Most self-pollinated plants produce little or no fruit and with cross-pollination between different clones, only 40-60 per cent of plants that have flowers produce fruit.

Moreover, Dr. Cutler observed honeybees aren’t efficient pollinators of some crops, while bumblebees are. He suggested a strategy when using honeybees is to set out a high number of hives—“pollination by brute force.”

He concluded that the number of bees in the field affects both initial and final fruit set and that clone genetics are also a big factor in pollination success.

His graduate student, Robyn McCallum, was also on the panel. She is examining conservation biology techniques for native pollinators. She wants her Master’s thesis to provide principles and tools for preserving biological diversity in pollinators.

McCallum said there is a challenge when there is a lack of either nesting habitat or food for pollinators. She is looking at habitat management to provide food or nesting to increase native pollinating insects and reduce the need to import hives.

The graduate student is examining increasing pollen resources by planting annual and perennial flowers along wild blueberry field edges. She is also looking at nest structures and has found that nests made from used milk cartons make the best housing, while wood posts with drilled holes are the worst.

McCallum found that planting buckwheat in fields will crowd out weeds; but when planted over sub-surface hardpan or during a drought, it will die out. Deer are also another negative factor in managing the crop. She said tillage of the buckwheat planting strip could be a positive factor, as is planting in shade or close to tree lines. She plans to look at drought as a factor in buckwheat development.

The student observed that marginal or out of production land could be planted to provide habitat and food to pollinators who really need food in the late summer.

Bumblebee quads should be placed in wild blueberry fields five to 10 days before the fields bloom, Bernie Watts told growers.

The Koppert Canada biological systems specialist noted that once they are in the field the bumblebees need a few days to recover from traveling and will forage on wild flowers before the wild blueberries bloom.

“Don’t store the quads. Get them into the field as soon as they arrive,” he advised growers. Quad colonies have a lifespan of six to eight weeks in the field.

Watts noted that bumblebees forage close to their quads, effectively increasing fruit set up to 100 metres away. He recommended placing quads on pallets or crates randomly along laneways or bare patches in the fields and fencing them in to prevent bear damage. They should also be kept at least 100 meters from honeybee hives, as honeybees tend to take food from the quads.

When relocating the quads for pollination, Watts told growers to close the bee door in mid-afternoon, then move the quad and re-open the door the next morning.

He recommended that growers dispose of their quads at the end of the season by burning them, and then order new ones in February. Quad stocking density varies from two to four per acre.

Panelist Tony Philips, a honeybee keeper, saw providing hives to blueberry growers as “an essential partnership” for him. “It is important to give good service when renting hives to growers.”

The WBPANS and the NS Beekeepers Association have prepared a contract for beekeepers and blueberry growers. Philips said it is good to be clear about what each party is responsible to do as it benefits both parties to establish a long-term relationship.

He said there should also be an extra payment for beekeepers who have to move hives during the rental period as its increases stress on the hives and bee mortality. He suggested prompt payment to the beekeeper for any rented hives. “Don’t make the beekeeper your banker.”

Growers should also have good field roads to expedite beehive handling and transport. Philips also recommended good electrical fencing to deter bear damage with the fencing kept at least three feet from the hives. Growers should not spray pesticide near the hives.

Growers should also anticipate their future need for hives by telling their beekeepers by July 2015 “what you will need for hives in May of 2016.”

Philips also felt it would be great if growers would actively solicit and encourage new entrants into beekeeping. Honeybees, he said, will pollinate a wide area and can complement bumblebees.

“It is important to have bee diversity, “Dr. Cutler observed. “There are studies that show, if you have bumblebees and honeybees, you do have more crop.”