Orchard Pollination: Honey Bees

European honey bees are the primary managed pollinators in orchards because their abundance can be managed from year to year.
Orchard Pollination: Honey Bees - Articles
Orchard Pollination: Honey Bees

Growers dependent on honey bees must constantly maintain a delicate balance between protecting their crops from pests and pathogens and protecting pollinators.

Due to competing demands, disease, the introduction of parasitic mites (mainly Varroa destructor), and likely impacts from insecticide and fungicide use in the field, however, the pollination picture has changed.

Despite intense efforts to protect their bees, beekeepers are losing large numbers of colonies to mites and the diseases they transmit. In addition, since 2006 there have been additional dramatic die-offs of tens of thousands of honey bee colonies from a phenomenon known as Colony Collapse Disorder (CCD). The result has been annual losses of around 30 percent of commercial colonies, which has left many beekeepers devastated and some growers without the quantity and quality of bees needed to pollinate crops. Fortunately the past few years have seen fewer losses attributed to CCD than at its peak between 2006 and 2014.

Healthy hives are key to maintaining high pollination activity during bloom because honey bees are vulnerable to many of the pesticides used to control insects, pathogens, and weed species. Growers dependent on honey bees must constantly maintain a delicate balance between protecting their crops from pests and pathogens and protecting pollinators. It is advisable to err on the precautionary side when using pesticides.

Recommendations for growers

  • Know the pesticides you are using and their toxicity to bees (do not depend on a third party to provide this information).
  • Read the label and follow the label directions.
  • Never use a pesticide on a blooming crop or on blooming weeds if honey bees are present.
  • The use of a pesticide prebloom, just before bees are brought onto a crop, is not recommended. If a pesticide must be used prebloom (for example, at pink in apples), select a material that has a lower toxicity to bees and a short residual toxicity, and apply only when bees are not foraging, preferably just after dark.
  • Do not apply insecticides postbloom (e.g., petal fall) until after the bees have been removed from the crop.
  • Blooming time varies depending on cultivars. Bees pollinating one variety or crop may be at risk while another crop or variety is being treated postbloom with insecticides. Also, while crops may have completed blooming, bees may be visiting blooming weeds in and around crops. Be aware of these situations and avoid the application of pesticides on a nonblooming crop if there is risk of drift onto blooming crops and weeds if bees are present. If a spray must be applied, use the least toxic material and apply only when bees are not foraging.
  • Protect water sources from contamination by pesticides. If necessary, provide a clean source of water close to honey bee colony locations prior to their arrival in the orchard or crop.
  • The mode of action of many fungicides in terms of toxicity to bees is unknown. Some are known to synergize with insecticides, and together these can be more toxic to bees. Avoid the application of the more toxic fungicides mancozeb and captan on blooming crops when bees are present. The use of and lime sulfur during bloom has been shown to be repellent to bees for several days as well.
  • For more information on toxicity, see also other resources online such as a Northeastern IPM guide on preserving wild pollinators and several online publications at a pesticide stewardship webpage.
  • Do not assume that organically approved compounds are safe to bees. More information on Organic Approved Pesticides.

As a result of high annual colony losses, fewer beekeepers are providing fewer honey bee colonies for growers and at much higher prices. In addition, the quality of honey bee colonies, at times, may be marginal for the purpose of pollination. Never before has the pollination situation been so critical. To ensure maximum crop yields, growers now must give careful attention and consideration to crop pollination.

Table 1-9. Toxicity of insecticides, miticides, fungicides, and blossom- and fruit-thinning agents to bees and suggested timing of application.

Active ingredients (example trade names)Highly toxicModerately toxicSlightly toxicNon-toxicGuidelines for timing of applicationsResidual toxicity
Insecticides
Abamectin/avermectin (Agri-Mek), ≤0.025 lb ai/AXApply only during late evening8 hours
Abamectin/avermectin (Agri-Mek), >0.025 lb ai/AXDo not apply on blooming crops or weeds1–3 days
Acetamiprid (Assail)XApply only in late evening, night, or early morning
Azadirachtin (Azatin, Neemix)XApply only in late evening, night, or early morningUp to 2 hours
Azinphos-methyl WSP (Guthion)XDo not apply on blooming crops or weeds4 days
Bacillus thuringiensis, Bt (Dipel)XApply at any time
Bifenthrin (Brigade), < 0.04 lb ai/AXApply only in late evening, night, or early morning
Bifenthrin (Brigade), 0.04 lb ai/AXApply only in late evening
Bifenthrin (Brigade), ≥0.06 lb ai/AXDo not apply on blooming crops or weedsUp to 1 day
Buprofezin (Centaur)XApply at any timeSublethal reproductive effects on adults within 24 hours of application; contaminated pollen lethal to larvae
Carbaryl 4F (Sevin), 1 lb ai/A or lessXApply only in late evening
Carbaryl 4F (Sevin), 2 lb ai/AXDo not apply on blooming crops or weeds
Carbaryl WP (Sevin)XDo not apply on blooming crops or weeds3–7 days
Carbaryl XLR (Sevin), ≤1.5 lb ai/AXApply only in late evening8 hours
Carbaryl XLR (Sevin), ≥1.5 lb ai/AXDo not apply on blooming crops or weedsLess than 2 days
Chlorantraniliprole (Altacor)XApply only in late evening, night, or early morning2 hours
Chlorpyrifos EC (Lorsban)XDo not apply on blooming crops or weeds4–6 days
Clothianidin (Clutch)XDo not apply on blooming crops or weedsIf applied before bloom, pollen and nectar will be contaminated
Cydia pomonella granulosis virus (Carpovirusine, Cyd-X)XApply at any time
Cyfluthrin (Baythroid)XDo not apply on blooming crops or weedsLess than 2 days
Deltamethrin (Decis)XApply only in late evening, night, or early morning4 hours
Diazinon EC or WPXDo not apply on blooming crops or weeds2 days
Dinotefuran (Venom/Scorpion)XDo not apply on blooming crops or weedsIf applied before bloom, pollen and nectar will be contaminated
Emamectin benzoate (Proclaim)XApply only in late evening, night, or early morning2 hours
Endosulfan (Thiodan, Thionex), ≤0.5 lb ai/AXApply only in late evening, night, or early morning3 hours
Endosulfan (Thiodan, Thionex), >0.5 lb ai/AXApply only in late evening8 hours
Esfenvalerate (Asana), ≤0.025 lb ai/AXApply only in late evening
Esfenvalerate (Asana), 0.0375 lb ai/AXDo not apply on blooming crops or weeds1 day
Fenpropathrin (Danitol)XDo not apply on blooming crops or weeds1 day
Flonicamid (Beleaf 50SG)XApply only in late evening, night, or early morning
Flupyradifurone (Sivanto)XApply only in late evening, night, or early morning
Formetanate HCl (Carzol), ≥1 lb ai/AXApply only in late evening12 hours
Horticultural mineral oilsXApply only in late evening, night, or early morning3 hours
Imidacloprid (Provado), ≤0.1 lb ai/AXDo not apply on blooming crops or weeds8 hours; if applied before bloom, pollen and nectar will be contaminated
Indoxacarb (Avaunt)XApply only in late evening, night, or early morning3 hours
Kaolin clay (Surround)XApply at any time
Lambda-cyhalothrin (Warrior), ≤0.02 lb ai/AXApply only in late evening
Lambda-cyhalothrin (Warrior), ≥0.03 lb ai/AXDo not apply on blooming crops or weeds1 day
Lime sulfurXApply at any timeRepellent for up to 7 days
Malathion ECXApply only in late evening6 hours
Malathion ULV, ≤3 fl oz ai/AXApply only in late evening, night, or early morning3 hours
Malathion ULV, 8 fl oz ai/AXDo not apply on blooming crops or weeds6 days
Malathion WPXDo not apply on blooming crops or weeds2 days
Methidathion (Supracide)XDo not apply on blooming crops or weeds3 days
Methomyl (Lannate)XApply only in late evening2 hours
Methoxyfenozide (Intrepid)XApply at any time
Novaluron (Rimon)XXDo not apply on blooming crops or weedsSublethal reproductive effects on adults within 24 hours of application; contaminated pollen lethal to larvae
Oxamyl (Vydate), ≤ 0.5 lb ai/AXApply only in late evening, night, or early morning3 hours
Oxamyl (Vydate), ≥1 lb ai/AXApply only in late evening8 hours
Permethrin (Ambush, Pounce), 0.1 lb ai/AXDo not apply on blooming crops or weedsUp to 2 days
Phosmet (Imidan), 1 lb ai/acreXDo not apply on blooming crops or weedsLess than 4 days
Potassium salts of fatty acids/soap (M-Pede)XApply at any time
Pyrethrins (Pyrenonee, Pyrocide)XApply only in late evening, night, or early morning2 hours
Pyridaben (Nexter)XApply only in late evening, night, or early morning2 hours
Pyriproxyfen (Esteem)XApply at any timeSublethal reproductive effects on adults within 24 hours of application; contaminated pollen lethal to larvae
RotenoneXApply only in late evening, night, or early morning
Spinosad (Entrust, Success)XApply only in late evening, night, or early morning2 hours
Spinetoram (Delegate)XApply only in late evening, night, or early morning2 hours
Spirotetramat (Movento)XApply at any time
Sulfoxaflor (Closer)XDo not apply on blooming crops or weeds; check isoclasttankmix.com before tank-mixing.14 days; if applied before bloom, pollen and nectar will be contaminated
SulfurXApply at any time
Tebufenozide (Confirm)XApply at any time
Thiacloprid (Calypso)XApply only in late evening, night, or early morning
Thiamethoxam (Actara)XDo not apply on blooming crops or weeds14 days; if applied before bloom, pollen and nectar will be contaminated
Miticides
Abamectin/avermectin (Agri-Mek), ≤0.025 lb ai/AXApply only during late evening8 hours
Abamectin/avermectin (Agri-Mek), >0.025 lb ai/AXDo not apply on blooming crops or weeds1–3 days
Acequinocyl (Kanemite)XApply at any time
Bifenazate (Acramite)XApply only in late evening, night, or early morning
Bifenthrin (Brigade), <0.04 lb ai/AXApply only in late evening, night, or early morning
Bifenthrin (Brigade), 0.04 lb ai/AXApply only in late evening
Bifenthrin (Brigade), ≥0.06 lb ai/AXDo not apply on blooming crops or weedsUp to 1 day
Clofentezine (Apollo)XApply at any time
Dimethoate (Cygon)XDo not apply on blooming crops or weeds3 hours
Etoxazole WDG (Zeal)XApply at any time
Fenbutatin-oxide (Vendex)XApply at any time
Fenpyroximate (Portal)XApply at any time
Formetanate HCl (Carzol), ≥1 lb ai/AXApply only in late evening12 hours
Hexythiazox (Onager, Savey)XApply at any time
Horticultural mineral oilsXApply only in late evening, night, or early morning3 hours
Spirodiclofen (Envidor)XDo not apply on blooming crops or weedsToxic to larvae w/ contaminated pollen
Plant Growth Regulators
Ethephon (Ethrel)XApply at any time
NAA/1-Naphthaleneacetic acidXApply at any timePossibly repellent
Fungicides
CaptanX
Lime sulfur, sulfurX
MancozebX
Sterol inhibitors (Indar/Nova/Rally/Rubigan)X
Strobilurins (Flint/Sovran)X

Insecticide toxicity is generally measured using acute contact toxicity values LD50 (the exposure level that causes 50 percent of the population exposed to die).
Toxicity thresholds are generally as follows to adult bees and indicated in the table:

• Highly toxic = acute LD50 of < 2/ μg/bee
• Moderately toxic = acute LD50 of 2–10.99μg/bee
• Slightly toxic = acute LD50 of 11–100μg/bee
• Non-toxic = acute LD50 of > 100μg/bee)

Do not return managed bees to the field until after the time period when residuals remain toxic. Additional label restrictions may apply; see pesticide label.

Source: Adapted from Hooven, Sagili, and Johansen (2013), “How to Reduce Bee Poisoning from Pesticides. Pacific Northwest,” Oregon State Extension Publication 591; May, Wilson, and Isaacs (2015), “Minimizing Pesticide Risk to Bees in Fruit Crops,” Michigan State University Extension Bulletin E3245, and unpublished data from Biddinger, Joshi, Rajotte, Shugure, and Phan.

Source: Penn State Tree Fruit Production Guide, updated January 2018