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Blueberry research continuing at NSAC

November 30, 1999  By Dan Woolley

The Nova Scotia Agricultural College has an extensive array of wild blueberry management research projects ranging from pollination to weed control.

The Nova Scotia Agricultural College has an extensive array of wild blueberry management research projects ranging from pollination to weed control.

Dr. Chris Cutler of NSAC’s department of environmental sciences is involved in a five-year research program, the Canadian Pollination Initiative (CANPOLIN), funded by a Natural Sciences and Engineering Research Council of Canada (NSERC) grant.


Dr. Cutler says researchers are interested in the interaction of bees with plants, the economic and ecosystems involved in pollination and the management of pollination to determine sustainable solutions to pollination problems and pollinator declines.

Wild blueberries are heavily dependent on pollination and a major horticultural crop covering a wide area of Eastern Canada with researchers working in Newfoundland-Labrador, Nova Scotia, New Brunswick and Quebec. The group is looking at wild bees in blueberry habitat, what drives their populations, how they can be promoted. It is also examining pollination patterns in fields.

Dr. Cutler says wild bees tend to be found near the edges of fields, while bees in hives are found in the centre of fields.
“A lot of things [people] consider as weeds – like sheep sorrel – are good attractants to bees,” he explains.

Toxicology is a big issue with blueberry production and bee management since bees can ingest poisons in nectar sprayed with toxic pesticides or by coming into contact with contaminated pollen, says Dr. Cutler.

Some pest control products are very safe, he adds. Belt is one of the best, he says, while Entrust – an organic product – is very toxic to alfalfa leaf cutter bees but not bumblebees. Delegate is very toxic to bumblebees when they ingest it, although it has no effect on them when it is topically applied. As for sublethal effects, Dr. Cutler notes oral ingestion of Serenade, a bio-fungicide, hinders brood production, while topical exposure to Moventa may stimulate brood production. Oral ingestion of Decis results in reduced lifespan and impaired reproduction in worker bees and significantly increased mortality in alfalfa leaf cutter bees.

There are many new control products coming in the next few years, Dr. Cutler says, adding that, following field trials with reduced risk insecticides in 2010, “we are doing a lot of stuff with bio-controls and predator beetles.”

Altacor could soon be registered and Cyazypyr, a good spanworm control product, is not yet registered on the crop, he says. Botanigard, a fungal biocide, is slower acting and had little or no effect, he adds.

Movento, not yet registered on the crop, did not work well on spittle bug, although Assail did, he observes. It also worked very well on fruit fly maggots and Admire and Movento – at lower rates – also gave some control, with Movento at higher rates working well on maggots. He adds that BYI02960, not yet registered, also worked well and Cyzazypyr at a higher rate gave good control.

Dr. Cutler notes bees can also be used as a vector for transmission of bio-control agents by passing through an enclosed tray containing a biocide dust that the bee then distributes to plants. Research on bees as biocide transmitters began in 2010 and will continue into 2011.

As there are a lot of data on toxicity in honeybees but not as much on bumblebees and alfalfa leaf cutter bees, Dr. Cutler says he will be extending his issue to cover these pollinators.

His research colleague, Dr. Nathan Boyd, who is examining weed management options in wild blueberries, has found Ultim to be one of the best controls for black bulrush. He is now examining Ultim as a control for other weeds. But it does damage blueberries, so Dr. Boyd is looking at when to apply Ultim, as it does suppress tickle grass, without eliminating it. He also notes Ultim is very effective on witch grass.

Burning also doesn’t reduce weed density, he observes, although some weed species will decline in numbers and others will increase.

Dr. Boyd says that while fescue is very sensitive to heat, and burning may reduce its seed bank, it will not control its population. Burning also will not kill mature tufts of fescue, but it can reduce seed populations in the tufts.

Dr. David Percival’s research focus at NSAC is wild blueberry leaf diseases. Three of them – septoria, rust and valdensinia – greatly interfere with the leaf’s ability to produce carbohydrates to nourish the plant by causing premature defoliation in the sprout year and premature fruit spoilage and loss of yield in the crop year.

Dr. Percival’s research is examining more than 15 products for application in the sprout year. He says fungicides have different windows for effectiveness, with Proline, particularly on sprouts, offering excellent suppression in the sprout year for septoria and rust.

Bravo and Proline work well on leaf retention and there were more flower buds, he says. Bravo and Proline also work very well together against valdensinia.

“We think there is a larger window of protection with these two fungicides in a tank mix,” he says.

Dr. Percival also recommends using Proline in a tank mix with Bravo to avoid resistance problems. Good suppression can also be achieved with just one application. He feels Proline is the best way to go with leaf diseases in the future.

“You have to stay on top of these leaf diseases,” he advises. “You have to keep going out to the field, even after harvest, to keep these leaf diseases at bay.”

Protect the plant canopy in the crop year for excellent fruit retention, he says.

As for future fungicides, Fontelis has excellent potential and BASF is developing a new product, under the trade name Lance, Dr. Percival says.

Triazole fungicides, used in blueberries for 30 years, show no apparent effect on spore germination and may not even inhibit spore growth, he says.

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