Introduction
Oregon is the largest producer of fresh blueberries in the U.S. — a feat accomplished through the help of honey bees. Blueberry growers and beekeepers work together to safeguard these essential pollinators when conducting pest-control applications. Learn what steps you can take to protect bees while fending off pests and disease.
Highbush blueberry (Vaccinium corymbosum) requires insect pollination to set high levels of fruit. Although blueberry flowers can self-pollinate, this typically does not happen without the assistance of insect visitors. Moreover, some blueberry cultivars will set larger berries when crossed with pollen from different cultivars, which is only possible when insects move pollen between flowers on different bushes. High rates of insect visitation during bloom are essential to sustaining blueberry yields for growers.
Blueberry flowers are unlike many Oregon fruit crops in that the pollen is not produced on the tips of anthers, but at their base, and is released through a pore at the end of a long tube. Bumble bees (Bombus spp.) are adept at shaking free the pollen from these poricidal anthers by vibrating the flowers, through a process known as sonication. Wild bumble bees, however, are at low densities when blueberries come into bloom, as the primary foragers are queens that have not yet initiated their nests.
Bumble bees are adept at shaking pollen from these poricidal anthers. Wild bumble bees, however, are at low densities when blueberries come into bloom.
Crops that bloom later in the year, such as cranberry and red clover, can have far larger numbers of wild bumble bees, as their colonies are approaching full strength and can field hundreds of foragers per colony.
Although there have been attempts to introduce managed bumble bees (Figure 1) for blueberry pollination, a combination of Oregon law prohibiting bumble bee species not native to Oregon and the high cost of managed native bumble bee species has resulted in a situation where commercial pollination is almost exclusively provided by managed honey bees (Apis mellifera).
Although honey bees are not as effective at dislodging or collecting blueberry pollen, they move enough pollen through nectar-foraging activity to set large numbers of fruit. Growers rented about 64,000 colonies for blueberry pollination in Oregon and Washington in 2023, costing growers $3.6 million in fees.
Blueberry growers and beekeepers have had a strong relationship that is mutually beneficial. Together, they have established standard practices, outlined here, to ensure sustained partnership around three key areas:
- Honey bee pollination (the strength, placement and timing of movement of honey bee colonies).
- Pest management during bloom.
- Maintaining clear communication among all growers, applicators, crop consultants and beekeepers leading up to the placement of colonies until their removal.
Honey bee pollination
Colony strength and stocking rate
A typical honey bee colony consists of a stack of boxes containing movable comb frames that the bees use to rear their young (known as brood) and store pollen and nectar (Figure 2). Typically, colonies delivered to blueberries consist of at least two boxes known as brood chambers. The queen roams freely in the brood chambers, laying eggs, which enables the colony to grow. As colonies grow in population, beekeepers may add additional boxes known as “honey supers,” which are restricted from the queen and are used for making honey. In addition, there may be one or more holes where bees enter and exit, known as entrances.
Strong honey bee colonies are required to ensure adequate pollination of blueberries. Colony strength is comprised of three parts:
- The size of the workforce of foraging workers.
- The size of the brood nest, which comprises the number of immature bees and their attending adult nurses.
- The presence of a laying queen.
A long-established Oregon regulation specified that colonies rented for “orchard crops,” such as blueberries, should have four standard (Langstroth-sized equipment) frames well-filled with brood and six standard frames well-covered with adult bees. Notably, these standards assume Langstroth equipment, whereas today many beekeepers frequently operate a box that is 75% the volume of a standard Langstroth box (Figure 3A). Also, while standard Langstroth equipment contains nine to 10 frames per box, some narrower Langstroth equipment contains only eight frames per box (Figure 3B). These regulations are currently not being enforced; see Evaluating honey bee colonies for pollination, PNW 623.
A grower can confirm the strength of colonies by contacting their beekeeper to open colonies; growers should never open or disturb a colony without the beekeeper’s permission. During an inspection, a beekeeper will split the boxes to inspect how many frames are occupied by bees. By looking down on a frame, a grower can count how many of the spaces between the frames (known as seams) are covered by bees as the beekeeper opens the boxes (Figure 4).
By averaging the seams occupied on the top and bottom of each box, a grower can estimate the number of frames of bees in a colony. Inspection is at the beekeeper’s expense, so it can help if growers preselect up to 10 colonies that they think are strong or weak.
One way to preselect colonies is to monitor the rate of returning foragers at the colony entrance. This method is quick but is less accurate than opening colonies. A grower surveying 5%–10% of the colonies using this method can readily identify dead colonies and gauge whether the beekeeper is delivering stronger-than-average colonies.
To use this method, wait two to three days after the colonies have been delivered and have settled in. Surveys should only be done when temperatures are 65°F and above, and when winds are less than 10 miles per hour. Also, the grower needs to identify all the entrances the bees are frequenting (Figure 2). In many cases, bees will enter through one primary auger hole in the top box. In other cases, bees may be using holes on the rear of the box.
Inspect the colony fully to find the dominant entrances before beginning a count. Colonies where no bees are seen returning to a hive entrance in one min may be dead; flag these with a surveyor stake on the exterior of the colony front.
In contrast, colonies where the rate of returning bees is consistently too rapid to count are considered strong (Figure 5).
Report any dead colonies to the beekeeper by texting the GPS coordinates of the colonies, along with a smartphone image showing the surveyor stake. The beekeeper can then replace them. You can also consider rewarding beekeepers who provide consistently strong colonies.
While extremes in colony size can be detected using the returning-forager-count method, it can be difficult to assess fine-scale colony strength.
The number of colonies per acre (known as the “stocking rate”) can also influence the number of bees pollinating the crop. Beekeepers have traditionally been advised to deliver three colonies per acre of blueberries.
Standard-sized colonies (four frames with brood and six frames covered with bees) at a standard stocking rate (three colonies per acre) are a good rule of thumb. However, new research indicates that a combination of colony strength and stocking rate are more important to pollination than the size of the population of bees in a single colony (“colony strength”).
“Stocking strength” is the product of the number of colonies delivered to a field and the average population of bees. A beekeeper providing stronger colonies (for example, eight to 10 frames of bees) may provide the same pollination at a lower stocking rate than a beekeeper delivering standard-sized colonies.
Stocking rate can also be influenced by:
- The total number of colonies within a 1-mile radius of the field (that is, counting colonies per acre at the landscape level, rather than by the number of colonies surrounding a specific block of blueberries (see Figure 6).
- A competing bloom adjacent to the blueberries. For example, a blooming mustard seed field may require a higher stocking rate.
- How difficult it is for bees to access the nectar from the flowers of certain cultivars. For example, the cultivar ‘Duke’ has a wide flower for honey bees to fit their heads through, whereas ‘Liberty’ has a narrow flower that makes it hard for honey bees to reach nectar. This, in turn, may necessitate a higher stocking rate. Consult with your beekeeper and OSU Apiculture Extension to determine if you would benefit from a higher stocking rate.
Timing of colony arrival and departure
Growers should establish clear expectations with their beekeepers, outlining in advance when colonies can arrive and when they should depart. Start the conversation in January or February, when beekeepers have a sense of how their colonies have survived the winter as well as the anticipated start of almond pollination (Figure 7.1). Follow up with beekeepers at bud break and again at the pink bud stage to firm up delivery dates (Figure 8).
Move colonies into fields at around 5%–10% bloom to ensure adequate bloom to hold the bees on the blueberries, so they do not seek bloom elsewhere (Figure 7.4). Bringing colonies into fields too early may result in an additional problem: Beekeepers won’t have enough time to prepare their colonies for blueberries after they return from California for almond pollination.
Beekeepers can also bring colonies before 5% bloom, provided there is little competing bloom and insecticide sprays have been completed (see next section). Moreover, growers should talk with neighbors about the crops they have planted and avoid planting crops that bloom at the same time as blueberries, such as mustard.
Blueberry pollination is one of the longest sets a beekeeper will have for a given year. A typical pollination will involve colonies on site for up to eight weeks, which can stress the colonies. OSU research has shown that beekeepers can report an increase in a brood disease (European foulbrood) over the course of blueberry pollination. For this reason, growers need to allow beekeepers to remove colonies as soon as possible after they have finished pollination. The grower and beekeeper should communicate at approximately 50% bloom (around the time of peak blossom color) to determine when the colonies should be removed (Figure 7.6).
Fields with multiple cultivars typically bloom at different times. To prevent bees from staying in blueberry fields too long, use the pattern of bloom to decide when colonies should come and go (Figure 7.6). For example, as early cultivars drop their petals, beekeepers should begin drawing down their colonies to avoid an excessive number of colonies given the remaining bloom.
Maintaining full stocking rates until all cultivars have stopped blooming can lead to high levels of competition among colonies, potentially weakening them, without contributing to additional pollination. Growers should plan to draw down colonies as early cultivars come out of bloom.
Blueberry growth stages
Figure 8. Timing for beekeeper notification should be based on stages of flower bud development.
Flower bud development
Flower development
Colony placement
Growers should establish clear expectations with their beekeepers, outlining in advance when colonies can arrive and when they should depart. Start the conversation in January or February, when beekeepers will have a sense of how their colonies have survived the winter (Figure 7.1). Reach back out to beekeepers at bud break and again at the pink bud stage to firm up delivery dates (Figure 8).
The ideal location for colonies during pollination is (Figure 7.3):
- Accessible by the beekeeper and free of obstruction during bloom, as the beekeeper will need to periodically manage colonies.
- In areas where moisture does not pool.
- At least 30 feet from the edge of the crop to prevent directly spraying the colonies with pesticides.
- Not directly adjacent to highways, as bees can collide with vehicles. This risks a dwindling of the pollinating workforce over time.
New research from Oregon State University and Washington State University on the popular cultivar ‘Duke’ has shown that colonies placed directly on the ends of blueberry rows on trestle posts (Figure 9A) are more likely to be exposed to pesticide drift than colonies set back and clustered together in locations such as sawdust piles (Figure 9B). Moreover, these studies have shown that fruit set and blueberry yield increase when colonies are placed in large clusters of 36–40 colonies, compared to dispersing four to eight colonies throughout the field.
Clustering colonies in locations that are easily accessible and are out of the way of farm equipment also decreases the amount of time beekeepers must spend managing hives. Whenever possible, growers should direct the beekeeper to place colonies in larger clusters and set back from the blueberry by 30 feet or more.
Growers should provide clear instructions for bee drop-off before the beekeeper’s arrival. Ideally, the grower and beekeeper should meet before bloom to discuss colony placement, as beekeepers will be placing colonies at night and may not be able to visually locate drop locations. Flag desired colony locations, as well as nearby wheel line irrigation tracks, to ensure correct hive placement and help prevent collisions between honey bee colonies and farm equipment.
Care of bees during pollination
Growers need to factor in beekeeper access to colonies during pollination to ensure colonies remain at full strength. Instruct farmworkers and outside contractors to maintain sufficient clearance around the pallet of beehives. Farmworkers should be made aware that disturbing bee colonies is a serious matter. Post signs at the front office reminding workers and contractors not to disturb the colonies (Figure 10).
Blueberry pest management and bees
The risk of pesticide application to honey bees is the product of four factors:
- The toxicity of the product to honey bees.
- The attractiveness of the blooms to bees.
- The residual time of the product (how long it remains toxic on the surface of a flower or leaf).
- The formulation of the product. The best way to protect bees from pesticides is to avoid all pesticide applications when bee colonies are present in the field.
Avoiding all pesticide applications during bloom is not always possible. Some pests cannot be managed effectively outside of the bloom period, and pest or disease pressure may increase or arise unexpectedly during bloom and require treatment. Restrict pesticide applications during bloom to days when:
- Temperatures are expected to be below 50°F.
- Temperatures are warmer from early evening up until 30 minutes before sunrise. (Figure 10, Table 1).
Also, do not apply insecticides that are toxic to bees unless they have a residual time of less than eight hours and the application occurs after dusk and before sunrise (Table 1).
Finally, there is growing concern around the use of adjuvants in conjunction with insecticide and fungicide sprays during bloom. While the science identifying which specific adjuvants pose a risk to bees remains incomplete, growers should avoid adding additional adjuvants when plants are in bloom.
|
Active ingredient |
Products |
Pest |
Toxicity to honey bees (label language)1 |
Residual toxicity (label language)2 |
RT25 values3 |
|---|---|---|---|---|---|
|
Prebloom insecticides |
|||||
|
Thiamethoxam |
Actara | Aphids | Highly toxic | Do not apply this product while bees are foraging in/or adjacent the treatment area. |
EPA: >72h Environmental hazards: >8h |
|
Acetamiprid |
Assail 30SG | Aphids | Toxic | Do not apply this product while bees are foraging in the treatment area. |
EPA: NA Environmental hazards: >8h |
|
Diazinon |
Diazinon 50W | Aphid, cherry fruit worm, winter moth | Highly toxic | Do not apply this pesticide or allow it to drift to blooming crops or weeds if bees are visiting the treatment area. |
EPA: >42h Environmental hazards: >8h |
|
Pyriproxyfen |
Esteem 35WP | Aphid, cherry fruit worm | No toxicity warning on label, but states: “Avoid direct application and/or spray drift to beehives.” | ||
|
Bacillus thuringiensis spp. aizawai |
Agree WG,Xentari dry flowable | Cherry fruit worm, winter moth | No toxicity warning on label. | ||
|
Cyantraniliprole |
Exirel | Aphid, cherry fruit worm | Highly toxic | Do not apply this product or allow it to drift to blooming crops or weeds if bees are foraging in the treatment area. |
EPA: <3h Environmental hazards: >8h |
|
Potassium salts of fatty acids |
M-Pede | Aphids | No toxicity warning on label. | ||
|
Malathion |
Malathion 8 Aquamul | Aphid, cherry fruit worm | Highly toxic | Do not apply this product or allow it to drift to blooming crops or weeds while bees are actively visiting the treatment area. |
EPA: 154h Environmental hazards: <8h |
|
Azadirachtin |
Aza-Direct | Aphids | No toxicity warning on label. | ||
|
Thiamethoxam |
Platinum | Aphids | Highly toxic | Do not apply this product while bees are foraging in or adjacent to the treatment area. |
EPA: >72h Environmental hazards: >8h |
|
Pyrethrins |
PyGanic 5.0 | Aphids | Highly toxic | Do not apply this product or allow it to drift to blooming crops or weeds while bees are foraging in the treatment area. |
EPA: na Environmental hazards: >8h |
|
Flupyradifurone |
Sivanto | Aphids | Toxic to adult bees in laboratory studies via oral exposure. However, not toxic to bees through contact exposure. Field studies conducted with this product have shown noeffects on honeybee colony development. | ||
|
Chlorantraniliprole |
Altacor | Cherry fruit worm, winter moth | No toxicity warning on label | ||
|
Indoxacarb |
Avaunt | Cherry fruit worm, winter moth | Highly toxic | Do not apply this product or allow it to drift to blooming crops or weeds while bees are foraging in the treatment area. |
EPA: 24h Environmental hazards: >8h |
|
Tebufenozide |
Confirm 2F | Cherry fruit worm, winter moth | No toxicity warning on label. | ||
|
Fenpropathrin |
Danitol | Cherry fruit worm | Highly toxic | Do not apply this product or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. | |
|
Spinetoram |
Delegate WG | Cherry fruit worm, winter moth | Toxic | This product is toxic to bees exposed to treatment during the three hours following treatment. Do not apply this pesticide to blooming, pollen-shedding or nectar-producing parts of plants if bees may forage on the plants during this time period. |
EPA: <3h Environmental hazards: <3h |
|
Spinosad |
Entrust | Cherry fruit worm, winter moth | Toxic | This product is toxic to bees exposed to treatment during the three hours following treatment. Do not apply this pesticide to blooming, pollen-shedding or nectar-producing parts of plants if bees may forage on the plants during this time period. |
EPA: <3h Environmental hazards: <3h |
|
Methoxyfenozide |
Intrepid 2F | Cherry fruit worm, winter moth | No toxicity warning on label | ||
|
Methomyl |
Lannate LV | Cherry fruit worm, winter moth | Highly toxic | Do not apply this product or allow it to drift to blooming crops or weeds while bees are actively foraging the treatment area. |
EPA: NA Environmental hazards: <8h |
|
Carbaryl |
Sevin XLR | Cherry fruit worm, winter moth | Highly toxic | Do not apply this product to target crops or weeds in bloom. |
EPA: >42h Environmental hazards: >8h |
|
Esfenvalerate |
Asana XL | Winter moth | Highly toxic | Do not apply this product or allow it to drift to blooming crops if bees are visiting the treatment area. |
EPA: NA Environmental hazards: >8h |
|
Bifenthrin |
Brigade WSB | Winter moth | Toxic | Do not apply this product or allow itto drift to blooming crops or weeds while bees are foraging the treatment area. |
EPA: NA Environmental hazards: >8h |
|
Bloom fungicides (with FRAC codes) |
|||||
|
Azoxystrobin(Group 11) |
Abound | Botrytis, anthracnose, alternaria | No toxicity warning on label. | ||
|
Captan (Group M) |
Captan 80WDG | Botrytis, mummy berry, anthracnose, alternaria | No toxicity warning on label. | ||
|
Fenhexamid (Group 17), Captan (Group M) |
CaptEvate 68WDG | Botrytis, mummy berry, anthracnose, alternaria | No toxicity warning on label. | ||
|
Fenhexamid (Group 17) |
Elevate 50WDG | Botrytis | No toxicity warning on label. | ||
|
Difenoconazole (Group 3)Cyprodinil(Group 9) |
Inspire Super | Botrytis, mummy berry | No toxicity warning on label. | ||
|
Isofetamid (Group 7) |
Kenja 400 SC | Botrytis | No toxicity warning on label. | ||
|
Fluopyram
(Group 7)Pyrimethanil(Group 9) |
Luna Tranquility | Botrytis, mummy berry, anthracnose, alternaria | No toxicity warning on label. | ||
|
Iprodione
(Group 2) |
Meteor | Botrytis | No toxicity warning on label. | ||
|
Fluazinam(Group 29) |
Omega 500F | Botrytis, anthracnose, alternaria | No toxicity warning on label. | ||
|
Polyoxin D zinc salt (Group 19) |
Oso SC, Ph-D WDG | Botrytis | No toxicity warning on label. | ||
|
Pyraclostrobin (Group 7) Boscalid (Group 11) |
Pristine | Botrytis, mummy berry | No toxicity warning on label. | ||
|
Azoxystrobin (Group 11)Difenoconazole
(Group 3) |
QuadrisTop, Quilt Xcel | Botrytis, mummy berry, anthracnose, alternaria | No toxicity warning on label. | ||
|
Cyprodinil (Group 9)
Fludioxonil (Group 12) |
Switch 62.5WG | Mummy berry, anthracnose, alternaria | No toxicity warning on label. | ||
|
Ziram (Group M3) |
Ziram 76DF | Mummy berry, anthracnose, alternaria | No toxicity warning on label. | ||
|
Fenbucibazole (Group 3) |
Indar 2F | Mummy berry | No toxicity warning on label. | ||
|
Prothioconazole (Group 3) |
Proline 480 SC, Tilt, PropiMax, Bumper | Mummy berry | No toxicity warning on label. | ||
|
Metconazole(Group 3) |
Quash | Mummy berry, anthracnose, alternaria | No toxicity warning on label. | ||
|
Pyraclostrobin (Group 7) Azoxystropbin(Group 11) |
Quilt Xcel | Mummy berry | No toxicity warning on label. | ||
1. Toxicity language is outlined in EPA’s Label Review Manual. Insecticides that kill more than 50% of test honey bees in laboratory trials (LD50) at a dose lower than 2 mg/bee are labeled “highly toxic to bees” under the environmental hazards section of the pesticide label. Insecticides with an LD50 less than 11 mg/bee but greater than 2 mg/bee are labeled “toxic to bees.” Products with LD50 values above 11 mg/bee will have no bee toxicity warning on the label.
2. Bee residual toxicity language is outlined in EPA’s Label Review Manual. Insecticides that dissipate within eight hours to levels that kill fewer than 25% of the bees (RT25) will have the following phrase on the label under environmental hazards: “Do not apply this product or allow it to drift to blooming crops or weeds while bees are actively visiting the treatment area.” Insecticides that remain toxic to bees after eight hours of weathering (RT25 > 8 hours) have the phrase: “Do not apply this product or allow it to drift to blooming crops or weeds while bees are visiting the treatment area.”
3. RT25 is the residual time needed to reduce the activity of the test substance and bring bee mortality down to 25% in cage test exposures to field-weathered spray deposits. EPA has published RT25 values. Where EPA has not published RT25 values, they have been inferred from the residual toxicity statement on the label (see point 2, above). Finally, recent research from OSU is also listed.
Pests and diseases around bloom
Blueberries are a high-value crop, and even small levels of damage can result in significant economic loss. Consequently, growers may need to control several insects immediately prior to bloom. These include aphids (including Ericaphis fimbriata and Myzus persicae), cherry fruitworm (Grapholita packardi) and winter moth (Operophtera brumata). Most of these insects can be managed by prebloom treatments, but on rare occasions, these pests require a cleanup spray during bloom.
A series of additional insect pests may require treatment following bloom. These include blueberry gall midge (Dasineura oxycoccana), root weevils (Otiorhynchus sulcatus, O. rugosostriatus, O. ovatus) and leafrollers (Choristoneura rosaceana and Argyrotaenia franciscana). Wait to treat crops for these insects until after removing honey bee colonies from fields.
Blueberry growers typically need to control a number of fungal diseases during bloom, most critically mummy berry (Monilinia vaccinii-corymbosi), botrytis blight (Botrytis cinerea), alternaria fruit rot (Alternaria spp.) and anthracnose ripe rot (Colletotrichum fioriniae). This can result in repeated applications of fungicides, frequently in tank mixtures of products with different FRAC (fungicide resistance action committee) codes to prevent the development of fungicide resistance.
Insecticides around bloom
Restrict insecticide sprays to the period before honey bees arrive in fields. Many products registered for insect pests in blueberries are toxic to bees. Some products, such as Malathion 8 for aphid and cherry fruitworm control, will remain toxic to bees on plant surfaces for up to a week. Apply them well before colonies arrive. Consult Table 1 for estimates of the residual toxicity of insecticides used during the prebloom phase.
Some insecticides are relatively nontoxic to honey bees. Use these during bloom if pest problems appear to require control. For caterpillar pests such as cherry fruit worm or winter moth, insecticides containing the active ingredients chlorantraniliprole or Bacillus thuringiensis subspecies aizawai are a good option.
If you need to apply an insecticide during bloom, inform the beekeeper under contract, as well as beekeepers in neighboring fields. Provide at least 48 hours’ notice of insecticide treatments. This will allow them sufficient time to move their colonies out of the field. Although moving beehives out of the field is possible, it is not practical to move bees out during sprays and bring them back later; this can result in lost pollination.
Moreover, when bees are in fields, contain runoff from the washing and rinsing of pesticide applications. Do not allow the runoff to pool in the range of bees gathering water (within a 2-mile radius of the colonies). These containment procedures are particularly important later in bloom, when temperatures warm and bees forage for water.
Fungicides around bloom
Unlike insecticides, there are no label restrictions associated with the use of fungicides. When disease pressure is high, fungicides may need to be applied on a seven- to 14-day schedule throughout the bloom period. In a drier year, a grower may only need two fungicide sprays: once before the bees arrive and a second during bloom.
Key fungicides such as iprodione and azoxystrobin have been found in pollen. These fungicides, used in disease management, have been associated with reduced honey bee colony survival, particularly when tank-mixed with insecticides. Avoid these products during bloom. If deemed necessary, restrict the use of iprodione and azoxystrobin products until early evening, when bees and pollen are much reduced in the fields.
Communication between growers and beekeepers
Industry communication
Every five years, representatives from OSU Extension, the Oregon Blueberry Commission and Oregon State Beekeepers Association meet to discuss provisions in the Bee Protection Protocol. They talk about new pollination needs, emerging pest and disease problems for each industry, pending Special Local Need pesticides, and other issues. Based on this dialogue, the groups may choose to revise this document.
Pollination contract
Recommended for new growers — some beekeepers and growers have long-lasting relationships and may not require a contract. See the Appendix.
Communication checklist
Beekeepers and growers should exchange cell phone numbers when entering a business relationship. It is typical to communicate via text message, which enables sharing map images or GPS coordinates. Best practices for communication between growers and beekeepers are:
Early season (mid-November–early January)
- Beekeepers and growers generally have wrapped up their management tasks by mid-November. This is a good time to touch base about the upcoming pollination and target hive numbers.
- If the grower is working with a new beekeeper, the grower and beekeeper should drive together to each field and map and flag loading and placement areas. Talk to the beekeeper about cultivars or blocks that experience low fruit set and where stocking rate should be boosted or decreased.
Bud break (March)
- Beekeepers will be finishing pollination in California almonds and will have a good sense of their numbers coming into blueberry pollination. Growers will also have a better sense of the crop's progress towards bloom. This is a good time to firm up colony numbers and rough out a delivery date for colonies.
10 days prior to moving colonies to the field (pink bud stage)
- Grower updates the beekeeper on the expected date of colony move-in.
- Grower to let the beekeeper know if there will be any issues applying prebloom insecticides close to move-in.
- Grower should provide at least 72 hours’ notice of when they want the colonies delivered, or some prearranged notice time.
Bloom
- Grower contacts beekeeper 48 hours before applying pesticides.
- Grower contacts beekeeper at 50% bloom (full bloom) to discuss the removal time of the bees from the crop.
References and resources
- Belsky, J., and N.K. Joshi. 2020. Effects of fungicide and herbicide chemical exposure on Apis and non-Apis bees in agricultural landscape. Frontiers in Environmental Science, 8.
- Brouwer, K.L., 2023. Impacts of Hive Placement on Blueberry Pollination and Pesticide Drift onto Hives. PhD thesis, Washington State University.
- Brouwer, K., M. Eeraerts., E. Rogers, L. Goldstein, J.A. Perkins, M.O Milbrath, A. Melathopoulos, J. Meyer, C. Kogan, R. Isaacs and L.W. DeVetter. 2025. Strategic honey bee hive placement improves honey bee visitation but not pollination in northern highbush blueberry. Journal of Economic Entomology, 118(1): 82-290.
- Eeraerts, M., E. Rogers, B. Gillespie, L. Best, O.M. Smith and L.W. DeVetter. 2023. Landscape-level honey bee hive density, instead of field-level hive density, enhances honey bee visitation in blueberry. Landscape Ecology, 38(2): 583-595.
- Fisher, A., C. Coleman, C. Hoffmann, B. Fritz, and J. Rangel. 2017. The synergistic effects of almond protection fungicides on honey bee (Hymenoptera: Apidae) forager survival. Journal of Economic Entomology, 110(3): 802-808.
- Goldstein, L.M., 2023. Assessing Honey Bee Hive Stocking Density and Colony Strength for Northern Highbush Blueberry Pollination. Master’s thesis. Michigan State University.
- Grant, K.J., L. DeVetter and A. Melathopoulos. 2021. Honey bee (Apis mellifera) colony strength and its effects on pollination and yield in highbush blueberries. PeerJ, 9, p.e11634
Acknowledgments
- This article is based upon work supported by the National Institute of Food and Agriculture (NIFA), U.S. Department of Agriculture, under award No. 2020-51181-32155 from the Specialty Crops Research Initiative.
- The protocol involved the close involvement of the Oregon Blueberry Commission and Oregon State Beekeepers Association, particularly the following individuals: Tom Cinquini (Sowers Apiaries), Matt and George Hansen (Foothills Honey LLC), TJ Hafner (Agricare Inc.), George Kaufman (Agricare Inc.), Andrew Lierman (Valley Agronomics LLC), Andy and Annie Steinkamp (Berries Northwest LLC) and Devesh Singh (Wilber-Ellis).
- Photos of blueberry growth stages resourced from a publication of Michigan State University Extension and used with permission of Michigan State University. © 2026 Michigan State University. All rights reserved.
Appendix: Sample pollinator contract
Pollination agreement
This agreement is made between _____________________________ (hereafter referred to as “Beekeeper”) and _____________________________ (hereafter referred to as “Grower”).
The terms of this agreement shall be for the DATE ______, CROP _____________________________ growing season.
Beekeeper responsibilities
The beekeeper shall supply the grower with hives (colonies) of honey bees to be delivered as follows:
- Approximate date of introduction: ______________________
- Approximate number of hives required:____
- Colony strength: An average of eight frames, with a minimum of five frames.
The beekeeper shall locate said bees in accordance with directions of the grower or, if none are given, according to their judgment in providing the maximum pollination coverage. The beekeeper agrees to provide colonies of the following minimum standards: honey bee colonies with a laying queen as evidenced by brood frames with brood and frames covered with adult bees (required strength as specified above) in deep hives with eight to 10 frames per hive. The beekeeper agrees to open and demonstrate the strength of colonies randomly selected by the grower.
The beekeeper agrees to maintain the bees in proper pollinating condition by judicious inspection, appropriate medication, treatments, and adding supers or removing honey as needed.
The beekeeper agrees to leave the bees on the crop until full petal fall or end of nectar flow as determined by the beekeeper or until traditional germination seasons are complete as determined by beekeeper or grower, whichever comes first.
Grower responsibilities
- The rental fee for the colonies will be ~$000.00 per colony for the period described above.
- The balance will be due in full at release date.
The grower agrees to provide a suitable location for the hives. The site must be accessible to a truck or other vehicles used in handling and servicing the colonies. The grower shall allow the beekeeper entry to the premises at all times. The grower assumes full responsibility for all loss and damage to his fields or crops resulting from the use of trucks or other vehicles in handling and servicing such colonies of honey bees.
The grower agrees not to apply pesticides highly toxic to bees to the crop while the bees are being used as pollinators. The grower shall not apply pesticides immediately prior (according to label) to the bees’ movement in the field or orchard if the residue would endanger the colonies.
The grower agrees to properly dispose of all pesticide solutions in such a manner that bees will not be able to contact the material while searching for a water source.
The grower agrees to give the beekeeper a 72-hour notice if hazardous materials not listed on this contract need to be applied. The cost of moving the bees away from and back to the crop to prevent damage from toxic materials shall be borne by the grower at the rate of ~$50 per hive. In addition, a mileage fee of ~$2.50 per mile per hive with a minimum of five miles movement may apply. Additional moves or setting shall require a fee of ~$50 per hive per move, after original setting.
The grower agrees not to touch, open, move, disturb or otherwise harass any beehives without the express written permission of the beekeeper.
The cost of the destruction of beehives due to any vandalism, movement, theft or relocation by trespassers, friends, family, the grower, agent or employees of the grower shall be borne by the grower or property owner at the rate of ~$200 per hive. PLEASE, for your own safety and fiscal liability and responsibility, do not touch the hives in any manner.
In addition, the grower agrees to provide adequate watering facilities for the bees if none are available within one-half mile of each colony used in pollinating the crop. The grower or property owner also agrees to hold harmless and without fault _____________________________, its agents, owners and employees in the event of any stinging incident.
Performance
It is understood and agreed that either party to this agreement shall be excused from the performance hereof in the event that, prior to delivery of the colonies, such performance is prevented by causes beyond the control of such party.
Grower signature: ________________________________________ Date:____/____/____
Mailing address:_______________________________________________
_____________________________________________________________
_____________________________________________________________
Day phone:_______________________ Night phone:_______________________
Beekeeper signature: ______________________________________ Date: ____/____/____
Mailing address:_______________________________________________
_____________________________________________________________
_____________________________________________________________
Cell phone: _______________________ Home phone: _______________________
About the authors
