Canola crops made possible by hard-working leafcutters

By Gillian Slade
Southern Alberta Newspapers – Medicine Hat

Those little triangular “tents” you see in some of the bright yellow fields of canola could be thought of as tent camping for bees — hard working bees, that is.

The tents/shelters provide ideal habitat for leafcutter bees that in turn work very hard pollinating female canola flowers to produce hybrid seed.
Canola grown for its commercial value as a crop is self-pollinating, said Cory Nelson, who farms near Burdett and is from a family that has been farming in the area for generations.

Canola grown for the seed is a different story, and that is where the leafcutters come in.

There are male and female canola seeds which are planted in stripes, and bees are needed to move pollen from the male plant flowers onto the female plant flowers, said Nelson. Generally there are 25 per cent male plants to 75 per cent female plants in a field.

“The seed that comes from that female plant will have higher yield potential,” said Nelson.

Agronomists monitor the canola growth to determine the optimum time for placing bees in the canola field to start pollinating, said Brady Glimsdale agronomist with Pioneer Hi-Bred Ltd., in Lethbridge. Once the first canola flowers start appearing, a judgment call is made on the day to have the bee-renting company arrive with the bees.

Leafcutter bees are supplied by companies such as Van der Stoel Pollinating Ltd., located at Enchant in the municipal district of Taber. They have been supplying leafcutter bees for about 20 years.

Leafcutter bees are needed in addition to honey bees because honey bees are most active when temperatures are cooler than 25 C. Leafcutter bees on the other hand like it hot and are more active when it is hot. They do not like getting wet though. The tents provide protection from rain and water during irrigation, said Nelson.

Each little tent holds a number of rectangular shaped boxes with numerous pencil sized channels and are about three or four inches deep. The leafcutters fill each channel with bits of leaf, honey and about six eggs.

Those cells are kept in cool storage over winter and are then incubated in preparation for going back into canola fields. The temperatures used and even the number of leafcutters supplied per acre of canola are trade secrets.

When they arrive on site, some leafcutters will have already hatched, and others will be very close to hatching, said Glimsdale. A formula is used to determine how many leafcutter bees are required, a trade secret, and they are ordered by the gallon of larvae.

According to online information, one alfalfa leafcutter bee can do the job of 20 honey bees, and based on observation in a greenhouse, 150 leafcutter bees can pollinate what it would take 3,000 honeybees to do.

While the leafcutter bee shelters are placed throughout the crop it is often possible to see honey bee boxes on a corner of a field. Honey bees will travel further than the leafcutters. Having a combination of honey and leafcutter bees covers all bases, plus irrigation of the crop, for maximum yield.

“I think a fairly common yield is between 30 to 40 bushels an acre,” said Nelson.

Male canola plants flower for fewer weeks than the female plants do. To mitigate that, with timing advised by agronomists, farmers trim the tops of some rows of male plants causing additional flowers to branch out from the sides about five or six days later, said Nelson. This prolongs the pollination season.