Pollination for Ohio orchards and small fruit

You plant a block of berries, a row of young apples, a patch of brambles, and then you wait to see what the weather and the insects will do with the flowers. Pollination is the step where that gamble gets decided. A flower that never receives pollen simply drops, and you carry the loss to market as a thin set, small fruit, or nothing at all.

The details cited in this entry were checked on read the fact sheet itself.

The Ohio State University fact sheet on bumble bees and solitary bees and wasps describes what is actually working the flowers in your orchard and berry rows. Much of that work is not done by honey bees at all. Bumble bees, ground nesting digger bees, sweat bees, leafcutting bees and a long list of solitary wasps all visit blossoms, and most of them ask very little of you in return. Knowing which ones nest where, when they emerge, and how they behave around people tells you how to protect them rather than fight them.

What a bumble bee colony actually does in your orchard

Bumble bees are the heavy lifters of early fruit set. They are stout, hairy insects banded in black and yellow, sometimes with orange or red markings, and they live in true annual colonies rather than the perennial hives you associate with honey bees. A colony starts when an overwintering queen emerges in May and hunts for a cavity: an old field mouse or rabbit nest, a hole in the ground, a stump, even an abandoned mattress or a bale of straw in a barn. She lines it with dry grass or moss, builds wax pots, and stocks them with pollen moistened with nectar into a stored food called bee bread.

The first brood of spring is small, five to ten workers, all female. They enlarge the nest and take over the foraging. By late summer the colony produces drones and new queens, those queens mate on a nuptial flight, and the fertilized females leave to find a place to spend the winter under loose bark or in a hollow tree. The rest of the colony dies with the first hard freeze. Total colony size usually stays under fifty individuals, so a bumble bee nest in a hedgerow is a modest neighbor, not a hive.

Their value to an orchard sits in the length of their tongues and the way they work a blossom. The fact sheet names the crops and plants they favor: clover, sunflowers, thistles, nettles, roses, partridge peas, raspberries, alfalfa. Bumble bees are also capable of buzz pollination, and their habit of foraging in cool, cloudy weather when honey bees stay home makes them the insect you want on the first open blossoms of the season.

Which bees are nesting under your berry rows?

Walk a block of raspberries in late April and you may see dozens of bees hovering low over bare ground or thin turf. Those are ground bees, also called digger bees. Several species occur in Ohio, almost all dark brown to tan and moderately hairy, about half an inch long. Males and females overwinter in burrows and emerge together in late April into early May.

The females clean old burrows or dig new ones in ground with little or no plant cover, throwing up a small mound of soil an inch high and three to four inches across, with the opening held in the middle. The bees are docile. The fact sheet is direct on this point: the females will only sting if you try to capture and hold one, and they would rather fly away than defend the burrow. The activity runs two to six weeks, and after a few rains the burrows vanish until the following spring.

Sweat bees are the small, dark or iridescent green insects that land on your forearm for the salt in your sweat. They nest in rotting wood or under loose bark, tunneling cylindrical passages that end in wider chambers. A sting usually happens only when a bee is trapped in a fold of skin or under clothing, and it rarely hurts for more than a few minutes. Leafcutting bees are the ones that leave half-inch oval notches in rose leaves. They are solitary, nest in hollow stems or in the pith of recently pruned canes, and line their burrows with those leaf sections. They do not defend territory aggressively, though a captured female can sting.

Where solitary wasps fit into pest control

Not everything nesting near your plantings is a pollinator. Digger wasps are predators, and each species specializes on one kind of prey. Some paralyze caterpillars, some take stink bugs, grasshoppers, crickets, or horse and deer flies, and they stock soil chambers with that prey before laying an egg on it. The larvae consume the still living insects, pupate by late fall, and wait until the next spring or summer to emerge.

The largest of the group is the cicada killer, a two-inch wasp with red-orange wings that provisions its brood with annual cicadas. The males carry no stinger, but they will fly at any moving animal that enters their territory and are known to strike people on the head and shoulders. The females can sting if handled, but the loud buzzing is mostly theater. Farmers who have lost sand-based ground to these wasps, on a playground or an athletic field, have found that a woven ground cloth under no more than four inches of sand keeps the soil out of reach while still draining rain.

What does weather do to a set?

Cold, wet, windy days during bloom slow every insect on this list, and bumble bees, which forage in cooler conditions than honey bees, cannot carry a whole block on their own. Rain during the window when blossoms are open washes pollen and keeps foragers in their burrows. A hard freeze after the colony has invested in brood kills the workers and ends that nest's season early.

Ohio's spring swings are the reason a single pollination event is never guaranteed. The queen bumble bee that emerges in May is timing her colony to the flowers that are open. A cold snap that stalls bloom, or a warm spell that pushes it forward past her emergence, leaves you with flowers and few insects to work them.

Should you remove ground nesting bees from a field edge?

In most situations, the fact sheet says, it is best not to eliminate ground nesting bees and wasps. They are valuable pollinators of agricultural and landscape plants, and many are useful predators that help control harmful pests. Control is recommended only when nests or burrows sit in areas people use often, and even then the best option is to avoid the area during the weeks the insects are active. Aerosol insecticides registered for bee and wasp control work only by contact, with little to no residual action, so they solve a single encounter rather than a season.

If you do need to reduce nesting, the lever is ground cover. Most of these insects nest in open areas or thin turf with soil showing through. Better vegetative cover, or mulch over bare patches, removes the invitation without touching the insects themselves. The publication warns that mowing over a bumble bee nest provokes workers that will pursue and sting repeatedly, so scout before you mow.

What the bees need close to the block

Bumble bee nests are generally found in habitats where flowering plants are nearby, and that is the practical takeaway for a farm. A hedge, a rough field edge, a few flowering perennials, and undisturbed ground give queens a place to overwinter and start a colony within foraging distance of your orchard or berry rows. Strip out every non-crop plant and you remove the housing along with the food.

Leafcutting bees work the pithy stems of pruned canes and broken branches, and rose growers, the fact sheet notes, are intolerant of the notched leaves. Those growers plug cut canes with a piece of wood or coat the cut end with melted candle wax to deny the bees a nesting tunnel.

Whether you farm apples, blueberries, raspberries or a mixed block, the insects described in the Ohio State fact sheet on bumble bees and solitary bees and wasps do most of their work without any management from you. The details on colony timing, nesting habits and stinging behavior come from that page, and readers who want the full account of each species can read the fact sheet itself.

Walk your own ground this spring and count what is flying. The burrows you see in late April, the bees hovering over thin turf, and the workers diving at you when you pass a nest are the same insects that set your fruit in June.