Leafcutter Bee (Megachile rotundata) Tour

July 19, 2019 — Hosted by John Wold, Ashlawn Farms, Laurel, MT

Attendees: Sheri Fredericksen, Gordon Clark, Mary Davis, Kyle and Pat Neary, Nan Grant, Carolyn Jones, Sue and Marvin Carter

Ashlawn Farms was established in 1909 and homesteaded by John Wold’s grandfather who moved west from Northwestern Minnesota. The name of the farm comes from the many ash trees located on the property. The family farms several crops, including some on dryland acres located south of Laurel. Leafcutter Bees (Bees) play an important role in the family’s alfalfa seed business which started in 1986.

In early years, a harrow was used to try and open the alfalfa flowers to allow pollination to occur, however, it was a practice that was destructive to the plant. During the 1970’s, farmers realized that bees worked extremely well to pollinate the alfalfa.

The alfalfa seed business is extremely weather dependent. Once the alfalfa plants begin budding, the Leafcutter Bee larvae, which have been stored in tubs during the winter, are placed into screened boxes. 19 Leafcutter 2The temperature in the incubation room is gradually increased to about 85 degrees for the larvae to mature into swarming Bees. Once the Bees begin swarming, they are hungry and ready to go to work. Ideally, if the weather can maintain about 80-85 degrees, the Bees are released to begin pollination of the alfalfa.20 Leafcutter 3

The Bees have no typical “queen;” however, the females do all of the work. The boxes containing the nesting holes are put into trailers and towed to locations where they are spaced out appropriately to pollinate the alfalfa. (The placement of the nesting boxes is 23 Leafcutter 6due to the Bees nesting range of 300 feet.) In total there are approximately 3,000 nesting holes per box. The trays of mature Bees are transported to the field by pickup (in the evening or morning) when the temperature is cool, and placed into the top of the trailers which can house 18, 24 or 28 nesting boxes. The screens are then removed. Once the temperature begins to rise, the Bees begin to swarm as they leave the boxes. The Bees are very weak and the first thing they do is learn to fly and begin to feed to gain strength. Once they build up strength, the females then choose a nesting hole.24 Leafcutter 7

Once a female Bee claims a nesting hole, it is hers and will not be used by another female while the eggs are being laid in the hole. The female Bee lines the hole with “cuts” of leaf material from nearby plants creating a sort of cocoon for depositing the pollen and nectar and laying the egg. The female Bee opens the alfalfa blooms and sucks the nectar and gathers the pollen from several 21 Leafcutter 4flowers on her belly and carries the pollen back to her nesting hole. (Since the females carry the pollen on their dry bellies, each flower they enter to gather more pollen is pollinated by the pollen that has been carried from the previous bloom.) The female Bee scrapes the pollen off inside the nesting hole, then spits the nectar into the pollen creating a paste-like food source for the larvae to feed on prior to diapause.1  When enough pollen and nectar has been collected, she then lays the egg and seals it with cuts of leaf material to protect the egg from predators. Female Bees literally wear their wings off flying into and out of the nesting holes and have a life span of about 5-6 weeks; the males live only about 2 weeks once they fertilize the females.

Approximately 6 gallons of Bees2 per acre are required to adequately pollinate the 22 Leafcutter 5alfalfa blooms. Great care is taken to ensure the alfalfa is not over-pollinated as it can have a detrimental effect to the alfalfa seed yield.

Once pollination is complete, the boxes containing the larvae are retrieved from the field and placed into the incubation room (at a temperature of 50-55 degrees) for the following year.3 The alfalfa plant is sprayed with a chemical defoliator causing the plant to dehydrate so that it is ready to harvest. One pound of alfalfa seeds equals approximately 250,000 seeds. Depending on the amount of alfalfa acres, the family’s total yield can vary year to year.

Leafcutter Bees have a gentle nature and although they have a stinger, would only sting if threatened. A sting is comparable to a mosquito bite. The Bee is renowned for their superior capability with pollinating alfalfa.

I “bee-lieve” a good time was had by all and the tour was very informative.

~ Submitted by Sheri Fredericksen

 

Footnotes

  1. Diapause is a predetermined period of dormancy, meaning it’s genetically programmed and involved adaptive physiological changes, i.e., from the time the larvae are placed into a cool temperature to the time the incubation room temperature is increased to make the larvae mature.
  2. Approximately 10,000 bees equals one pound.
  3. The larvae will remain in diapause until the incubation room temperature is increased the following summer to begin the metamorphosis cycle into mature Leafcutter Bees.