The squash bee specifically pollinates pumpkins and squash; using the all-purpose honeybee for these fields may not be useful
RIDGETOWN, Ont. — Farmers often view honeybees as all-purpose pollinators, but in some situations they’re not particularly useful.
Entomologist Jim Chaput says some uninformed growers bring commercial hives to their pumpkin and squash fields, but this practice provides only a minimal benefit. The species they really need is peponapis pruinosa, the squash bee.
“Their only source of food is from squash and pumpkins,” Chaput said during the Diagnostic Day held at the University of Guelph’s Ridgetown Campus July 9-10.
“The female comes out in the summer. We know they are able to find pumpkin and squash fields within three kilometres. We don’t know the biology well enough to know how far they can really go.”
The squash bee is the No. 1 pollinator of cucurbita species. Bumblebees are No. 2.
Farmers can help by only shallow cultivating fields with squash and pumpkins. Another technique is to stake out known nesting areas and avoid cultivation altogether.
The ground-nesting bees prefer light soil with bare patches. Their nests reach 12 to 22 centimetres in depth and often feature four to five chambers, each containing a single egg.
The larvae survive underground over the winter as pre-pupae and emerge as adults in July.
The male adults are busiest in the early morning, looking for females and blooms. Once the flowers have closed, males can often be found sleeping inside.
Don’t be afraid to check. Squash bees have no sting.
Adult bees are 11 to 14 millimetres in length, larger than honeybees. They are black and have yellowish to tan hairs on most of the head and thorax. The abdomen is black with whitish bands.
One survey of squash and pumpkin fields in the U.S. Midwest identified the bees in 19 out of 20 sites. Bee numbers ranged from 10 to 120 bees per 100 flowers.
Chaput said native pollinators are being viewed with increasing interest, especially with the decline of the honeybee population.
Susan Chan, a former Ontario bee inspector, said there are many other examples of farm-friendly native pollinators, and their activity should not be taken lightly. For example, increases of 10 to 30 percent in oilseed crop yields have been linked to strong native pollinator populations.
Chan said one of the simplest things farmers can do is leave the natural areas of their property alone.
“You can also improve a hedgerow that’s already there by planting some extra native species and taking out things that are not helpful, or that hedgerow could already be perfect. Above all, don’t rip it out,” Chan said previously at the Guelph Organic Conference.
Planting trees, shrubs and other flowering plants to which pollinators are attracted will help, especially if producers want something in bloom all the time.
Certain crops can also be managed to benefit pollinators. For example, instead of harvesting a hay crop at 10 percent bloom, wait until 15 percent of the flowers have opened.
Chan said it is a small step but can have a significant impact when combined with similar initiatives.
Farmers and other landowners with a strong interest in developing their pollinator resources should try to encourage blooms from spring to mid-fall. Having blooms of different colours and shapes will encourager greater pollinator diversity.
On her own Ontario rural property, Chan aims at having three plant species in bloom throughout the growing season.
“If you’re looking to improve pollinator habitat, it’s more complex than just planting things on the farm,” she said.
There are five major bee families in many areas of temperate North America: apidae, which includes bumblebees, honeybees and many solitaire species; andrenidae, the mining bees; halictidae, the sweat bees; megachilidae, the leafcutter and mason bees; and colletidae, the cellophane bees.
There is a wide array of ground-nesting species. Other species nest above ground in a variety of abodes including sumac and second-year raspberry canes. Chan said raspberry growers may wish to leave old raspberry canes stacked near the new growth for the season instead of burning them.
The distance that bee species fly from their nesting sites varies widely. Domesticated honeybees will travel up to three or four kilometres away, bumblebees up to one km and smaller species from 100 to 500 metres.