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Conserving Wild Bees in Pennsylvania

Wild bees, which include native and naturalized bees, pollinate a variety of crops. In areas of Pennsylvania, wild bees already provide the majority of pollination for some summer vegetable crops.

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Updated:

July 15, 2025

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Wild bees like this bumble bee are essential to Pennsylvania agriculture. Credit: Nash Turley

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Wild bees are critical for the health of our ecosystems and for pollinating crops. These bees look and live very differently from honey bees and have recently faced drastic declines. How can we help them?

Ways to Help Wild Bees

We can conserve and attract wild bee species in Pennsylvania by increasing the amount of floral resources in the area, conserving natural habitats in the landscape, creating or conserving nesting sites, and reducing bee exposure to pesticides.

Bumble bee on tomato flower — Bumble bee on a tomato flower at Penn State's community garden.

Ouch, That Stings!
Bees have a reputation for producing painful stings, partly because of stings inflicted by hornets, yellow jackets, and other wasps. However, most wild bees are not aggressive because they are solitary nesters and thus do not have large colonies to defend. The risk of getting stung by a wild bee is low.

Conserve Natural Habitats

Many studies have shown that wild bee diversity increases as the proportion of natural habitat in the surrounding landscape increases. Forests, meadows, and wetlands provide wild bees with nesting sites and floral resources, especially early in the spring when flowers may be scarce. Fortunately, community groups can work with nonprofit organizations, conservation land trusts, and local municipalities to acquire and protect natural lands through grant programs like the Community Conservation Partnership Program (C2P2), managed by Pennsylvania's Department of Conservation and Natural Resources (DCNR). Land managers can also conserve natural habitats on their properties by maintaining flowering plants in their field margins.

When selecting plants to add to your landscape, consider the following characteristics:

Native plants: Prioritize growing native plant species as these support more pollinators than non-native plants. Native plants are well adapted to the local weather and soil conditions and they have co-evolved with the insect communities in our region.

Diversity of plants: Growing a wide variety of plant species will help support the most number of bee species. Select plants which have flowers of a variety of shapes, sizes, colors, and blooming times.

Right plant, right place: Plants will grow best in regions where they are well adapted. Select plants that are appropriate for local soil and light conditions. Pollinator-friendly plant guides are useful tools for finding appropriate native plants for your area (see Resources).

Preserve Nesting Sites

The vast majority of bee species are solitary (over 90%) meaning individual female bees build their own nest rather than living in large social colonies. These nests are built in a wide variety of locations and habitats. Approximately 70% of bee species build nests in the soil while the rest nest in cavities above ground, mostly in dead wood and plant stems. Many species are particular in their nesting locations and highly variable environments will help provide nesting sites for the most bee species. Reducing or elimination tilling and not spraying pesticides are also ways to help preserve nesting habitat. Nesting sites for bees can include:

Bare ground
Dead wood or logs
Dried plant stems
Dense vegetation
Forest floor

Reduce Bee Exposure to Pesticides

Bees may be poisoned or killed when they come into contact with pesticides found on leaves and flowers on which they forage or the soil where they nest. Insecticides are harmful to bees but so are herbicides and fungicides. All pesticides should be reduced where possible. When chemical controls are necessary, take special care by:

Choosing products that target the pest organism.
Choosing the least harmful formulations to pollinators.
Treating plants when their flowers are not blooming.
Applying chemicals in the evening when bees are not active and many flower buds are closed.
Preventing pesticide drift onto flowering crops or natural areas

Cellophane bee (Colletes sp.) at the opening of her underground nest

Planting Cover Crops

Cover crops are plants grown in agricultural fields and gardens for a number of reasons, including reducing erosion, increasing soil fertility, and suppressing weeds. If allowed to bloom, some cover crops can also help support bee populations. However, take care to terminate the cover crop before it sets seed to avoid any potential weed problems. Examples of flowering cover crop species:

Cover crops - buckwheat, hairy vetch, and clover — Examples of flowering cover crop species: Buckwheat (left), Hairy Vetch (middle), Clover (right)

Importance of Wild Bees to Agriculture

There are over 400 species of wild bees in Pennsylvania. Wild bees are any bee that is not a honey bee and they pollinate a variety of crops, including apples, pears, nuts, strawberries, tomatoes, peppers, blueberries, squash, and melons. In areas of Pennsylvania, wild bees already provide the majority of pollination for crops. Conserving wild bee populations is essential for sustaining agricultural production in Pennsylvania.

Other tips for providing floral resources throughout the growing season include:

Planting flowering herbs within the crop field.
Setting aside marginal land for bee habitat by establishing hedgerows of flowering woody plants or native perennial plants.
Harvesting flowering crops, like alfalfa, in strips rather than all at once.
Allowing a portion of leafy crops to bolt (produce flowers).

The Wide Variety of Wild Bees

Bees come in a wide variety of shapes, sizes, and colors. Some are hairy and have a robust shape with yellow markings, like you expect from familiar bumble bees. But many more are small and slender, are not noticeably hairy, and have a variety of colors ranging from black to metallic green. Some of the most diverse and abundant bees are frequently confused with wasps, like those in the photos below. Behaviors among bees are also highly variable. For example, many species only visit particular species of plants, and some species are parasitic, meaning they do not collect pollen at all and instead lay their eggs in the nest of other bees.

Bees Important to Pennsylvania Agriculture

Approximately 4,000 described bee species exist in North America. More than 400 species occur in Pennsylvania and many are important crop pollinators.

Bumble Bees (Bombus spp.)

These large-bodied bees have the ability to buzz pollinate (vibrate pollen
off anthers). They are social bees and colonies are established each spring
by a single queen.

Sweat Bees (Family Halictidae)

There are over 100 species in Pennsylvania of these small bees that
range in color from metallic blue and green to brown and black. Most species are solitary, and a few are attracted to the salts in human sweat.

Leafcutter bees (Megachile spp.)

These solitary bees are black with white, silver, or orange hairs. Females frequently nest in rotting wood and line the interior with small pieces of leaves. Unlike most bees that carry pollen on their hind legs, leafcutter bees transfer pollen on the underside of their abdomens.

Squash bees (Xenoglossa pruinosa)

The squash bee is an efficient pollinator of squash plants and related crops. This solitary, ground-nesting species will visit flowers at temperatures and under light conditions that are unsuitable for most other pollinators.

Longhorn bees (Melissodes spp.)

These fast-flying and solitary species are most active during late summer
and fall. They nest in the ground and sometimes in large aggregations. Males have long antennae and can be found sleeping in groups in flowers or on plant stems.

Mason bees (Osmia spp.)

Mason bees are prized for their efficient pollination of orchard crops in spring. Both native and introduced species have been successfully managed by providing nesting boxes or tubes that can be stored in a sheltered location over the winter.

Mining bees (Andrena spp.)

These solitary bees are rightfully termed "mining bees" for their habit of excavating underground nests. These are among the first bees to emerge in the spring and many only collect pollen from certain types of plants.