NEWS for North Dakotans
Agriculture Communication, North Dakota State
University
7 Morrill Hall, Fargo, ND 58105-5665
July 9, 1998
The industrious honeybee is being enlisted to help boost the yield of sunflowers grown for oil and to battle one of the crop's pests.
North Dakota State University researchers found that honeybees can carry Bacillus thuringiensis, commonly known as BT, to sunflower heads. BT is a bacteria that kills the larvae of moths and butterflies, including the banded sunflower moth, a significant pest of North Dakota sunflowers. NDSU entomologist Gary Brewer and graduate student Jawahar Jyoti also discovered that the bees improve pollination and seed set even in sunflowers which are largely self-pollinating.
"North Dakota is a big bee state. And sunflowers are an important crop here," says Brewer.
Last year, North Dakota was the country's top sunflower producer and second in honey production. North Dakota farmers grew more than 1.1 million acres of sunflowers for oil. Beekeepers in the state had 245,000 colonies and produced $18 million of honey.
"Broadcast insecticides are a beekeepers' biggest enemy," says Don Nelson, a Moorhead, Minn., beekeeper who supplies bees for NDSU research. "Anytime we can get away from broadcast sprays, we'll be better off. And I depend on sunflowers for my livelihood, so anything I can do to help sunflower producers is great."
Brewer notes that sunflower producers often notify beekeepers of spraying plans so they can take steps to protect their bees. But closing up or moving hives takes time and cuts honey production.
"To avoid that, we thought about making bees part of the pest solution," Brewer says.
In the 1940s researchers discovered that bees in apple orchards in Washington state could transmit apple diseases such as fire blight. Forty years later, researchers developed a device to dust bees with bacteria that fought fire blight.
"In North Dakota, we knew that pest insects were moving into the fields at the same time as bees are working," Brewer says. "So why couldn't we use the same technique?"
Brewer and Jyoti built a BT applicator to be placed at hive exits. As bees left the hive they were covered with BT. Despite instinctive efforts to clean themselves, the bees still carried and deposited enough BT on sunflower heads to kill the larvae of banded sunflower moth. Control of the moths in one-acre plots was as good as control provided by spraying BT and other pesticides.
But it turns out that the bees do not even need to be carrying BT to benefit sunflowers.
A yield boost of up to 5 percent due to improved pollination and seed set in the test plots was a pleasant surprise in the research, Brewer says. Other researchers have reported yield increases of up to 15 percent. This summer the researchers are taking a closer look at that yield boost.
"If we can get a yield boost from improved seed set that is greater than the loss caused by a pest, we're still getting a net increase," Brewer says. "We may not need to use BT at all." In some plots, spraying pesticides for the sunflower seed weevil cut honeybee activity so much that the loss in seed set outweighed any benefit from killing the weevils.
Brewer expects the yield increase to vary by sunflower variety. The researchers have also found that oil content increases in some varieties when researchers use bees to improve pollination.
If the research results continue to show promise for boosting yields and oil content, producers may need to start considering the effect sprays have on honeybees as well as on crop pests.
Although the research is promising, Brewer cautions that additional research is required before recommendations can be issued to growers and beekeepers. "We need to know how many bees it takes to get these results and we need to look at the best placement of hives," Brewer says. "Beekeepers would like hives close to the edge of the field for accessibility, but to be most effective they may need to be in the center."
"The fact that this approach works is a big step in the right direction," notes beekeeper Nelson. "But there are still a lot of questions. A bee is going to go where it wants to within a 2-mile area, so unless we get all the sunflower producers in an area to cooperate, we're still going to have problems with spraying." He also notes that providing the BT and maintaining the hives to provide insect control will mean additional material and management expense for beekeepers. "Paying for that is also an issue that needs to be worked out."
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Sources: Gary Brewer (701) 231-7908 & Don Nelson (218) 291-1105
Editor: Tom Jirik (701) 231-9629