Can native pollinators provide free services for growers?

PHOTOS PROVIDED At left, a squash bee deep inside a pumpkin flower. Notice the pollen grains on its hairy legs.

With winter officially over and the warmer temperatures moving in, beekeepers will be able to open hives and fully assess their health.

For some, it might be a search for the queen. Can she be spotted on any of the frames? If not, are there any eggs (evidence of the queen) or brood?

If the hive is healthy and growing, it might be time to switch some boxes around to stimulate more growth before the major nectar flow.

For other beekeepers, the tasks may be a bit less joyful. For these beekeepers, time is spent brushing dead bees off frames and getting them ready for reuse.

This task is becoming more common as colony losses in Pennsylvania are reaching about 50 percent every year. Winter losses in 2016-2017 were 52 percent but dropped slightly in 2017-2018 with 46.7 percent. It will take a few months to fully determine the losses from this past winter.

At right, both a bumblebee (foreground) and squash bee (background) exit a pumpkin flower.

Fruit and vegetable growers are well aware of the issues surrounding honeybees and are looking at alternatives to make sure their crops are fully pollinated. Researchers are working closely with these producers to determine if native pollinators can replace the services of the honeybee.

Penn State’s Dr. Shelby Fleischer has been studying pumpkin fields the past several years to determine what is visiting flowers.

The problem with pumpkin pollen is that it is large and sticky. So much so that wind cannot do the work (like pollen in sweet corn) and requires insects to move it from the male flowers to the female flowers. His research shows that 37 different bee species are visiting these flowers. Most visitations are from two wild species, the squash bee and the common eastern bumblebee, plus the honeybee. A great deal of effort is looking at capitalizing on these free pollinating services from the wild species.

The squash bee has a very intimate relationship with pumpkins (and other cucurbits) as it utilizes the pollen to raise their young. No other flowering plant can fulfill this role.

Unlike the honeybee which is a social cavity nester, in managed hives or hollowed out trees – both above ground, squash bees are solitary and live in the ground. To encourage a stable or robust population, areas of the garden/farm should be no-tilled or left alone as this will promote nesting sites.

The bumblebee is also a ground nester but differs from the squash bee in that they live in a social arrangement (queen with workers and drones that have specific tasks). But instead of relying on one species of plant for their survival, bumblebees feed on diverse floral resources.

To encourage their population, some nearby soil should remain undisturbed (just like the squash bee) and alternative floral sources from other plant species should be nearby.

There is nothing wrong with some pockets of the yard/garden/farm going weedy. The broadleaf weeds will flower and can provide the alternate floral sources necessary for the bumblebee population.


Tom Butzler is a horticulture educator with the Pennsylvania State University Cooperative Extension Service and may be reached at 570-726-0022.


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