North Dakota State University

Figure 1. Hover fly with few hairs. Photo by Veronica Calles-Torrez, NDSU

By Veronica Calles-Torrez, North Dakota State University (NDSU); Esther McGinnis, NDSU; Patrick Beauzay, NDSU; Nathaniel Walton, Michigan State University Extension; Joy Landis, Michigan State University; Janet J. Knodel, NDSU

Editor’s note: This article was a joint collaboration between North Dakota State University and Michigan State University Extension.

Everyone knows that bees love to visit flowers, but not everything that you see visiting flowers or buzzing around the garden is a bee. In fact, many insects imitate bees in order to avoid unwanted attention. Whether you call them “bee-mimics,” “wanna-bees” or “yellow-stripey-things,” most are beneficial helpers in our yards and gardens. This brief guide will help you tell some of these insects apart.

Flies

Figure 2. Hairy honey bee (Apis mellifera) on sedum. Photo by Veronica Calles-Torrez, NDSU

Some flies, especially hover flies and bee flies, can be mistaken for bees because their body form, color and hair patterns, buzzing sounds and behaviors mimic bees. Flies have a set of front wings (forewings), but the hind wings are small, knob-like balancing organs called halteres, so flies appear to have only two wings (Figure 1, red circles). Bees have well-developed forewings and hind wings.

Figure 3. Hover fly. Photo by Veronica Calles-Torrez, NDSU

Flies have large compound eyes that occupy most of the head, while bees have narrow compound eyes on the sides of the head. Most flies that resemble bees have short, three-segmented antennae, while bees have longer, cylindrical antennae of 12 (female) or 13 (male) segments.

Some flies, especially bee flies, can be hairy like honey bees (Figure 2), bumble bees and digger bees, and can hover and move quickly from flower to flower while foraging, just like bees. Flies do not sting people.

Hover flies (Family: Syrphidae)

Figure 4. Bee fly. Photo by David Cappaert, Bugwood.org

Several hover fly species (Figures 1 and 3) resemble bees in coloration, behavior and size. Most hover flies are 5 to 15 millimeters long and have large heads with reddish or marbled black eyes, two clear wings and black and yellow color patterns on the abdomen and sometimes on the thorax. Some hover flies are quite hairy while others are not.

Hover flies buzz and hover like bees around flowers. They feed on pollen and nectar, often using the same flowers that bees do. Some hover fly larvae are aphid predators and provide biological pest control.

Bee flies (Family: Bombyliidae)

Figure 5. Paper wasp. Note the waist between the thorax and abdomen. Photo by Veronica Calles-Torrez, NDSU

Bee flies (Figure 4) are about 7 to 15 millimeters long and have stout bodies covered with yellow, black or brown hairs. Different species can have transparent or patterned wings. Bee flies have a long proboscis (tongue) and feed on pollen and nectar.

Wasps

Figure 6. Honey bee collecting pollen from aster flower. Note the pollen basket on its hind legs. Photo by Veronica Calles-Torrez, NDSU

Similar to bees, wasps have four developed wings, long segmented antennae and a distinctly visible narrow “waist” (Figure 5) due to a constriction between the thorax and abdomen. Bees also have a constricted waist, but it isn’t readily visible. Wasps are much less hairy than most bees (Figures 2 and 6). Wasps’ hairs are not branched, while bees’ are branched, but you will need a microscope to see this.

Most bees have special pollen-collecting hairs on their hind legs and collected pollen is easy to see (Figure 6). Leaf-cutting bees collect and carry pollen on hairs underneath their abdomens. Also, wasps have brighter colorations and patterns, and wider range of color and pattern variations than bees.

Yellowjackets, hornets and paper wasps (Family: Vespidae)

Figure 7. Eastern yellowjacket. Photo by Jon Yuschock, Bugwood.org

These insects are strikingly patterned with black and yellow. They hold their wings folded lengthwise over their bodies like a jet. Yellowjackets (Figure 7) are approximately 12 to 25 millimeters long. Their face is mostly yellow, except for black eyes and black antennae. Yellowjackets have yellow and black bands on the abdomen and usually nest in the ground.

Paper wasps (Figure 5) are approximately 25 millimeters long with black, yellow and sometimes orange markings. Nests are constructed of paper, often underneath house eaves.

Figure 8. Bald-faced hornet. Photo by Johnny N. Dell, Bugwood.org

Bald-faced hornets (Figure 8) are black with white markings and are about 15 to 25 millimeters long. The tip of the abdomen often has white markings. Nests are constructed in trees and sometimes roof peaks. Bald-faced hornets are usually aggressive and sting when their nests are disturbed.

Cicada killers (Family: Crabronidae) (Figure 9) are large wasps 20 to 50 millimeters long. They have a yellow face brick-red eyes and a black abdomen with yellow bands. Wings are lightly infused with brown and the legs are red. As its name implies, Cicada killer wasps prey on cicadas. They do not have nest guarding instincts like wasps and honey bees. These impressive looking wasps are not aggressive, but females do have stingers and can sting when they feel threatened.

Figure 9. Cicada killer wasp. Photo by Johnny N. Dell, Bugwood.org

This article was published by Michigan State University Extension. For more information, visit http://www.msue.msu.edu. To have a digest of information delivered straight to your email inbox, visit http://www.msue.msu.edu/newsletters. To contact an expert in your area, visit http://expert.msue.msu.edu, or call 888-MSUE4MI (888-678-3464).

Blueberries at harvest display poor pollination. Right cluster was visited by bees while left cluster was not. Courtesy Michigan State University Extension

By Esther E. McGinnis, North Dakota State University; Nathaniel Walton and Erwin Elsner, Michigan State University Extension; Janet Knodel, North Dakota State University

Bees are important insect pollinators for bountiful home vegetable gardens and backyard fruits. Both European honey bees and native bees, such as bumble bees, help ensure fruit set and higher yields. Learning about the process of pollination can help smart gardeners attract and safeguard these important insects.

What is pollination?

Figure 1. Flower anatomy in a perfect flower. Courtesy Michigan State University Extension

Pollination is the deposit of pollen grains from the anther (male structure) onto the pistil (female structure) of the same plant species (Fig. 1). Pollen can be transferred within an individual flower or between separate flowers. Successful pollination results in the production of viable seeds and a fruit to protect them.

Most crop plants are pollinated by insects or wind. Many agronomic crops, such as wheat and corn, rely on wind pollination. In contrast, many fruits and vegetables require or benefit from insect pollination. Common insect pollinators include bees, butterflies and flies. Of these pollinators, bees are the most important in home gardens.

The role of pollinators in the vegetable garden

Common plants in the cucurbit family include cucumbers, squash, zucchini, pumpkins, watermelon and muskmelon. Most cucurbits depend on bee pollination because each plant produces separate male and female flowers rather than having both sets of reproductive parts in each flower.

Figure 2. Cucumber flowers. Female flower with ovary on left, male on right. Courtesy Michigan State University Extention

Gardeners frequently ask why they have so many flowers on their cucumbers, but no fruit set. Look closely at the flowers to answer this question. In many cucumber cultivars, the first set of flowers are all male, which do not bear fruit. Both male and female flowers will then be produced in the second wave of blooms.

If female flowers are present but no fruit develops, then the problem may be a lack of pollinators. In the short-term, you can fill the role of the bee with hand- pollination. Take a clean paintbrush and insert it into the male flower to gather pollen. Then, transfer pollen to the stigmas of an open female flower. Hand-pollination works best in the morning. For a long-term solution, create pollinator habitat near or in the garden to attract bees.

Such flowers are called “imperfect.” Bees are essential to cross-pollinate or carry pollen from the male flower to the receptive female flower.

Figure 3a. Tomato flower anthers forming a tube around the pistil. Courtesy Michigan State University Extension

The cucurbit male flower contains three to five stamens with pollen- producing anthers. The female flower produces a single style with three stigmas. The easiest way to distinguish between the two flower sexes is to look for an ovary below the yellow petals. Female flowers have a swollen ovary or fruit and male flowers do not (Fig. 2).

Figure 3b. Portion of anthers cut away to revel pistil. (Courtesy Michigan State University Extension

In contrast to cucurbits, Soloanaceae crops such as tomatoes, peppers and eggplants produce “perfect” flowers that contain male and female reproductive structures. Flower anatomy differs from the idealized image in Figure 1. Tomato anthers form a tube that completely surrounds the pistil (Fig. 3a). Figure 3b shows the anthers partially removed to reveal the pistil. Tomatoes, peppers and eggplants can be pollinated simply by wind shaking the pollen from the anthers onto the stigma. However, bumble bees can improve fruit set and size because they vibrate the flowers and shake pollen loose from the anthers.

Leafy greens (lettuce, spinach, arugula), cole crops (cabbage, broccoli, cauliflower, kale), root crops (carrots, beets, radishes, onions), legumes (peas, beans) and tuber crops (potatoes) do not require bees to produce an edible harvest.

The role of pollinators in growing fruit

Bee pollination is important for growing tree fruits and small fruits. Many tree fruits such as apples and pears are self-incompatible (Table 1). This means two separate cultivars must be planted to produce fruit. For example, a ‘Honeycrisp’ apple blossom will not set fruit if a bee deposits pollen from a second ‘Honeycrisp’ apple tree. Instead, the pollen must come from a cultivar that is genetically different and has an overlapping bloom time.

Fruits such as sour cherries are self-compatible and can set fruit in the absence of a second cultivar (Table 2). However, self-compatibility still requires bees to transfer pollen within the flower or between flowers for full pollination. The number of cherries on a tree is directly related to the number of bee visits.

Raspberries are another example of a self-compatible fruit that relies on bees for full pollination (Table 2). The average raspberry flower contains 100 to 125 pistils. To produce a normal berry that does not crumble, at least 75 to 85 of the pistils must be pollinated.

Best management practices to attract and protect pollinators

Plant native and other well-adapted flowering plants for season-long bloom in or near the garden.
Create nesting habitat for ground- and cavity-nesting bees.
Do not spray insecticides or fungicides on flowering plants or fruit trees just before or during bloom.
If pesticide applications are necessary, choose a product with the least toxicity to bees.

Resources

Bee-utiful Landscapes: Building a Pollinator Garden from NDSU Extension
Bees of the Great Lakes region and wildflowers to support them from MSU

For more information on a wide variety of Smart Gardening topics, visit www.migarden.msu.edu or call MSU’s Lawn and Garden hotline at 1-888-678-3464.

Download a printable PDF: Smart Gardening: Pollination in vegetable gardens and backyard fruit

This work is supported by the Crop Protection and Pest Management Program 2017-70006-27175 from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

This article was published by Michigan State University Extension. For more information, visit http://www.msue.msu.edu. To have a digest of information delivered straight to your email inbox, visit http://www.msue.msu.edu/newsletters. To contact an expert in your area, visit http://expert.msue.msu.edu, or call 888-MSUE4MI (888-678-3464).