Many native bees are effective pollinators

May 30, 2018 Cranberry Home & Garden

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More than 4,000 species of native bees have been identified in North America. In Pennsylvania, more than 400 species of native bees have been documented. Above, a honey bee on an apple blossom.

Honey bees (Apis mellifera), commercially important pollinators for many agricultural crops, are not native to North America.

Honey bees were introduced by European colonists in the 1600s.

Since 2006, declining honey bee populations have caused concern among bee keepers, agricultural growers and scientists. This decline has spawned research on the value of native bee species as pollinators.

Many native bees are effective and efficient pollinators. Some native bee species can pollinate plants that honey bees are unable to pollinate.

More than 4,000 species of native bees have been identified in North America. In Pennsylvania, more than 400 species of native bees have been documented.

Examples of native bees found in Pennsylvania include: common eastern bumble bee (Bombus impatiens), squash bee (Peponapis pruinosa), and blue orchard mason bee (Osmia linaria).

Bumble bees live in colonies and are active over a long season, February to November. Look for these in the early morning and when the weather is cool and cloudy.

Bumble bees forage over a wide range of plant species and perform a behavior called “buzz pollination,” in which the female clasps a flower in her jaws and vibrates her wing muscles to dislodge pollen from the flower.

Many plants, including a variety of wildflowers and crops like tomatoes, peppers, and cranberries, benefit from buzz pollination. Bumble bees also are able to act as pollinators in a greenhouse.

Squash bees are solitary, ground-nesting bees that are specialized pollinators of squash, pumpkin, melon and other related crops. Like bumble bees, they are active in the early mornings and at lower temperatures, when other pollinators are not active.

The blue orchard mason bee is a solitary species that is active early in the spring. Mason bees will fly in poor weather conditions, which gives them an advantage for pollinating early orchard crops, spring flowers and nuts.

The hairy abdomen of the female mason bee provides a location for carrying pollen, which falls off easily as she moves from flower to flower. Research has shown that an entire tree could be pollinated by six mason bees, an accomplishment that would otherwise require 360 honey bees.

The Japanese hornfaced bee (Osmia cornifrons) was introduced into the United States by the U.S. Department of Agriculture in the 1970s and now is established in the wild throughout most of Pennsylvania. The Japanese hornfaced bee is found with the blue orchard mason bee in areas adjacent to fruit orchards.

Groups of native bees with multiple species in Pennsylvania are leaf cutter bees (Megachile SPP.), sweat bees (Halictus SPP.) and mining bees (Adrena SPP.).

Similar to mason bees, leaf cutter bees are solitary and carry pollen on their abdomen.

Sweat and mining bees are small bees that nest in the ground or rotting wood.

Mining bees are often the first bees to emerge and are pollinators of early spring blooming trees and wildflowers from March to May.

Sweat bees are often shiny, metallic colored bees that can be attracted to the salts in human perspiration.

Home gardeners can attract native bees by providing a wide variety of native flowering plants; limiting or discontinuing pesticide use; providing nesting habitats such as sunny, bare spots of soil, dead trees or, specifically for mason bees, a nesting box or tubes in a sheltered location.

A consistent water source, such as a water-filled flat dish with small rocks and stones for landing, benefits bees during hot weather.

By attracting native and honey bees, home gardeners will be rewarded with more blooms and better production of flower, vegetable and fruit crops.

Mary Alice Koeneke is a retired biologist who enjoys birdwatching and gardening. As a Penn State Extension Master Gardener Butler County (Class of 2016), she is especially interested in gardening for birds, pollinators, and wildlife using native plants.

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