The Hazard Travels With the Flowers: Pollinator Exposure From Perimeter and Barrier Treatment

1. Introduction: the half of the job that reaches outside

This journal has covered what pest control does to the technician and what it does to the target. It has not covered what it does to everything else outdoors, and that is a gap worth closing.

The short version is that the interior work is close to irrelevant to pollinators and the exterior work is not.

1.1 Why the distinction is the whole article

An industry that treats the question as a single yes or no gets it wrong in both directions. It either accepts blame for interior work that harms nothing, or it dismisses concern about exterior work that does.

2. The indoor assumption

The regulatory position on interior treatment.

Indoor uses are generally assumed not to have a reasonable potential for exposure of bees to pesticides, with exceptions occurring such as greenhouses where bees are used.⁷

2.1 What follows

Cockroach gel in a kitchen, rodenticide in a bait station inside a wall, bed bug treatment in a bedroom and crack and crevice application indoors are not pollinator issues.

That is worth saying plainly, because a general anxiety about pesticides attaches to all of it equally and the evidence does not support that.

3. The outdoor assumption

The contrasting position.

In general, outdoor spray applications are assumed to have a reasonable potential to result in exposure of adult bees and their brood to pesticides if they are applied to pollinator attractive crops or drift to pollinator attractive plants during periods when bees are likely to be foraging.⁷

Exposure to bee brood and other castes in hives is expected when exposure to foraging bees is identified, as foragers will bring residues back to the hive.⁷

3.1 The condition that does the work

The assumption is conditional on reaching pollinator-attractive plants, either directly or by drift, during foraging periods. It is not a blanket statement about outdoor application.

So the operative question on any given job is whether attractive plants are present and in bloom, which is an observation a technician can make on arrival.

That is an unusually favourable position to be in. Most of the risk trade-offs in this journal turn on information nobody has, such as whether a population is resistant or how long a tick was attached. This one turns on whether the shrub beside the foundation is in flower, which requires no instrument and no laboratory.

3.2 The hive amplification

That foragers carry residues back to the hive means exposure of one individual becomes exposure of a colony.⁷ This is the same horizontal transfer principle this journal described as an advantage in cockroach baiting, operating here as a liability.

4. The four exposure routes

How a pollinator actually encounters a product.

Pollinators can be exposed through direct contact with pesticides or residues that remain active on foliage and flowers; in nectar and pollen for systemic treatments drawn up through a plant's vascular system; pesticide drift into areas where bees are foraging, nesting or gathering nesting material; and pesticide runoff that contaminates water that bees forage on or the nesting beds of ground-nesting bees.³

4.1 The route that surprises people

Ground-nesting bees are a large share of wild bee diversity, and runoff reaching their nesting beds is a route that has nothing to do with flowers at all.³

A perimeter treatment applied to soil at a foundation line is in the same medium those bees nest in. We are not aware of work quantifying that specific overlap and flag the observation as ours.

4.2 The herbicide point

Few herbicides are toxic to insect pollinators, but many kill plants that provide nectar and pollen for bees.³

That is an indirect effect on the food supply rather than a toxic one, and it belongs in the picture because lawn weed control removes exactly the flowering weeds §5 is about.

4.3 The systemic complication

Insecticides applied by trunk injections, soil applications, or sprays are designed to remain active on leaves, stems, or even flowers, and those residues can be hazardous to pollinators. Systemic insecticides applied to soil as granular or liquid formulations, or as trunk injections, will move into the plant and possibly into the flowers.⁸

4.4 Why systemic is harder to manage

A contact residue sits on a surface and can be avoided, covered or removed. A systemic active is inside the plant and arrives in the nectar of flowers that had not opened when the treatment was made.

The guidance is correspondingly blunt about dose: precise rate and frequency of application are crucial, and never guess the amount of pesticide you are applying, with use rate and frequency named as the two concerns with application methods.⁸

5. The lawn experiment

The controlled study that anchors this paper.

Researchers noted that despite label precautions not to apply them to blooming plants, neonicotinoids and other residual systemic insecticides may be applied for preventive control of lawn insect pests when spring-flowering weeds are present, and that while dietary exposure to neonicotinoids adversely affects bees, the extent of hazard from field usage is controversial.¹

They exposed colonies of the bumble bee Bombus impatiens to turf with blooming white clover treated with clothianidin, a neonicotinoid, or with chlorantraniliprole, the first anthranilic diamide labeled for use on lawns. Sprays were applied at label rate and lightly irrigated. After residues had dried, colonies were confined to forage for six days, then moved to a non-treated rural site to openly forage and develop.¹

5.1 Why the design is good

Label rate, normal irrigation, dried residues, and a defined exposure period followed by development at a clean site. The colonies were not dosed; they foraged on a treated lawn the way they would in a suburb.

6. What happened to the colonies

The outcome.

Colonies exposed to clothianidin-treated weedy turf had delayed weight gain and produced no new queens, whereas those exposed to chlorantraniliprole-treated plots developed normally compared with controls.¹

6.1 Why no new queens is the severe endpoint

A bumble bee colony is annual, as this journal set out for yellowjackets. Its entire function is to produce the queens that found next year's colonies.

A colony that gains weight slowly has been harmed. A colony that produces no queens has failed completely, because nothing of it survives the winter. That is a more consequential endpoint than worker mortality.

It is also an endpoint no field observation would detect. Nobody walks past a bumble bee nest in September and notices that it failed to produce queens. A mortality event leaves dead insects on the ground; a reproductive failure leaves nothing to see at all, which is part of why this class of harm is easy to discount.

6.2 The product difference

Two products applied to the same turf at label rate produced completely different outcomes. The hazard is specific to chemistry rather than general to treatment, which means product selection is a real lever.¹

7. The absence of avoidance

The finding that removes a comfortable assumption.

Neither bumble bees nor honey bees avoided foraging on treated white clover in open plots.¹

7.1 Why anyone would have expected otherwise

It is intuitive that an insect would detect and avoid a toxic surface, and this journal has documented exactly that behaviour elsewhere, in repellency to pyrethroids and in glucose aversion in cockroaches.

Here it does not happen. The bees forage normally on treated blooms, which means the exposure is not self-limiting and the presence of foraging activity after a treatment is not evidence that the treatment was safe.

7.2 Why the asymmetry is not surprising on reflection

Detection and avoidance evolve where the compound, or something like it, has been part of an organism's history. Cockroaches encountering pyrethroids and developing avoidance is a population under decades of selection in the environment where the exposure occurs.

A bumble bee encountering a systemic residue in clover nectar has no such history and no reason to have evolved a response to it. We offer that as reasoning rather than a sourced explanation; the study reports the absence of avoidance without accounting for it.

7.3 The operational consequence

A technician cannot rely on pollinators leaving a treated area. If blooms are present and attractive, they will be worked.

That removes the most common informal reassurance offered on this subject, which is that the bees will simply go elsewhere.

8. What was in the nectar

The measured concentration.

Nectar from clover blooms directly contaminated by spray residues contained 171 plus or minus 44 parts per billion clothianidin.¹

8.1 Reading the figure

This is nectar from blooms hit directly by the spray, not from a systemic uptake pathway. The contamination route here is the simplest one: the flower was open when the product landed on it.

That is the route §9 shows can be eliminated.

9. The mowing result

The most useful finding in this paper.

Notably, neither insecticide adversely impacted bee colonies confined on the treated turf after it had been mown to remove clover blooms present at the time of treatment, and new blooms had formed.¹

9.1 What this establishes

The turf was treated. The ground still held residue. New flowers grew from treated plants on treated soil, and colonies foraging on those flowers were not measurably harmed.

The hazard was carried by the blooms that were open at the moment of application, and removing those blooms removed the hazard.

9.2 The authors' conclusion

The results validate label precautionary statements not to apply neonicotinoids to blooming plants.¹

That is an unusual outcome. A study set out to test whether a label precaution mattered and found that it did, which is worth recording because this journal has more often found label standards lagging the evidence.

9.3 The caveat that limits this

The mowing result should not be generalised beyond what it tested, and the regulatory guidance supplies the reason. Pre-bloom foliar application of pesticides to pollinator attractive crops may also result in exposure to bees if the pesticide is persistent and may translocate to pollen and nectar after spray application.⁷

9.4 What that means in practice

Removing open blooms removes the contact route. It does not remove a translocation route in a product persistent enough to move into flowers that open later.

The experiment found no harm to colonies on the re-bloomed turf with those two products at those rates,¹ which is evidence about those products rather than a general rule. A more persistent or more systemic active applied to the same ground could behave differently, and we would not tell a client that mowing makes any treatment safe.

10. Why that result matters most

It converts a values argument into a scheduling problem.

If the hazard were inherent in treating turf or foundations at all, the only responses would be to stop or to accept the harm. If the hazard is carried by open blooms present at the moment of application, then mowing, covering, avoiding or timing eliminates most of it.

10.1 The cost of the fix

Mowing a lawn before a treatment costs a homeowner nothing they were not going to do anyway. Covering a flowering shrub during a perimeter spray costs a technician a few minutes.

We would state plainly that a hazard avoidable at that price has no defence for occurring, and that this is our position rather than a sourced one.

11. The barrier spray assessment

The finding that names this industry directly.

A 2025 assessment concluded that on a site by site basis, residential mosquito sprays, in particular barrier sprays performed by private companies, likely pose a significant risk to pollinators.⁴

11.1 Why this is the sharpest version of the problem

A residential mosquito barrier treatment is applied to vegetation, by design, because that is where adult mosquitoes rest. Vegetation is also where pollinators forage and shelter.

Unlike a perimeter band at a foundation, the target surface and the pollinator habitat are the same surface. There is no version of the treatment that reaches one and not the other, which makes timing and plant selection the only available controls.

11.2 The scale of the practice

Residential mosquito barrier treatment has grown into a substantial consumer service, and it is offered on properties chosen for having vegetation, shade and moisture, which are the same features that make a yard useful to pollinators.

We are describing our own industry's fastest-growing outdoor service and we do not have figures for its extent in this province. That it is named specifically in the assessment, rather than insecticide use in general, is the part we think practitioners should sit with.

11.3 The comparison with municipal work

A municipal adulticide programme is intermittent, publicly noticed, conducted under a permit or an order, and subject to buffer provisions, as this journal set out. A private barrier treatment is recurring, applied directly to vegetation, and subject only to the label.

Those are different exposure profiles, and the more heavily governed one is not obviously the larger contributor. We flag that comparison as ours and note we have no data comparing the two.

12. What that assessment measured

The method, and its limits, which the authors state.

Researchers calculated risk quotients for specific pyrethroids and three species of butterflies, and found levels of risk tied to moderate to high levels of risk in many yards.⁴

The calculations utilized acute contact LD50 values, used to investigate the acute risk to honey bees and butterfly caterpillars coated by insecticides when the sprays occurred.⁴

12.1 What that does and does not cover

Acute contact toxicity at the moment of spraying is one exposure scenario. It does not address chronic dietary exposure, sublethal effects, or the colony-level outcomes that §6 measured.

A risk quotient is a calculation rather than an observed kill. We would describe this as a well-founded hazard estimate rather than a measurement of harm, and note the authors present it as an initial assessment.

13. The species we know nothing about

The honest state of the evidence base.

We also don't know much about the direct toxic effects, or acute toxicity, of pesticides on pollinating insects outside of honey bees, alfalfa leafcutting bees and some bumble bees.³ Scientists don't yet know the effect of long-term exposure of pollinators to low doses encountered over a lifetime.³

The barrier spray authors make a parallel point: most insect populations are not monitored, so there are potentially other declining taxa present in yards treated with mosquito sprays.⁴

13.1 What that means for the argument

The toxicity data underpinning pollinator risk assessment rests on a handful of managed or well-studied species. The wild bee fauna of a Canadian yard is not those species.

That uncertainty runs in the unhelpful direction. An unstudied species is not thereby a safe one, and absence of evidence of harm to most pollinators reflects absence of study rather than absence of effect.

13.2 The habitat context

Site-level management including planting a diversity of flowering plants can help counter the landscape-wide impact of urbanisation, and home gardeners have contributed to that effort. But even when habitat is present in urban areas, pollinators and other beneficial insects can still be negatively impacted by pesticide use, with background contamination detected in urban greenspaces including natural areas, community gardens and yards.⁴

14. Mosquito control as a pollen contaminant

An independent line of evidence on the same activity.

Pyrethroid insecticides associated with mosquito abatement were found to be a major contaminant of pollen collected by honey bees in one state, and a large bee-kill occurred in another in 2016 after an aerial application of an organophosphate insecticide.⁹

14.1 The connection to the previous article

This journal examined Winnipeg's municipal mosquito programme separately. The relevant point here is that mosquito adulticide is named in the pollinator literature as a category of concern alongside agriculture, forestry and landscape management.³

That programme's own published position is that larviciding is the most effective approach, and larvicide applied to water is not an application to flowering vegetation. The non-target argument points the same direction as the efficacy argument did.

15. The label instrument

How this is regulated.

Additional Pollinator Protection Labeling is required for pesticides, including all neonicotinoid class insecticides registered for foliar use outdoors. From 2014, neonicotinoid product labels were required to have a pollinator protection portion including a bee advisory box with general information on routes of exposure and spray drift precautions, and a Directions for Use portion providing mitigation options.⁵

15.1 The framing the extension source offers

The same source puts the underlying point bluntly: it is important to remember the purpose of insecticides, they kill insects.⁵

That is the sentence the industry's marketing language tends to avoid, and it is the honest starting point for any conversation about non-target effects.

15.2 The regulatory range

Labelling is not the only instrument that has been used. At least one jurisdiction adopted an administrative rule prohibiting the application of four neonicotinoid insecticides.⁶

So the available responses span advisory labelling at one end and prohibition of named actives at the other, which is the same regulatory spectrum this journal described for cosmetic pesticide policy in this province.

15.3 The tiered directions

The Directions for Use accompanying those labels describe different scenarios, distinguishing crops under contracted pollination services from food crops and commercially grown ornamentals not under such contract.⁶

That structure ties the requirement to whether managed bees are known to be present. It has no obvious analogue for a residential garden, where wild pollinators are present and nobody has contracted for anything.

16. What the advisory box says

The content of the requirement.

The box contains advisory language on different routes of exposure for bees, covering contact from foliar application and ingestion of nectar and pollen from seed treatment, soil treatment, trunk injection and foliar application; on best management practices to reduce exposure to bees, including reducing drift; and on how to report bee kills.⁶

The two precautions identified are direct contact with foliar residues and ingestion of residues in pollen and nectar.⁸

16.1 The reporting provision

That the label tells an applicator how to report a bee kill⁶ is worth noting, because it presumes kills occur and establishes a route for recording them.

Section 19 suggests that route is not heavily used.

17. Drift distance

How far the question extends beyond the treated area.

Regulatory assessment has considered that bees exposed to spray drift extend 1000 feet from the edge of the treated field.⁶

For one compound, all crops and application methods where on-field exposure was expected produced exposure concentrations exceeding the risk levels of concern for bees, and even where on-field exposure was not expected, an off-field spray drift assessment indicated there could be risk from all foliar uses.⁶

17.1 The urban translation

A thousand feet from a treated field is agricultural framing. In a residential setting that distance spans many properties, and the neighbours whose gardens fall inside it were not party to the decision.

We flag that translation as ours. The figure is from field-scale assessment and we have not seen it applied to residential perimeter work.

18. Aged residues

How the risk changes with time since application.

A residual toxicity study indicated that aged residues at 48 hours did not cause significant increases in bee mortality by contact, and that the primary risk concern post application is through dietary routes of exposure.⁶

18.1 The two-day window

Contact hazard declines substantially within two days for that compound. Dietary hazard, through contaminated nectar and pollen, persists because it is carried in plant tissue rather than on a surface.

That distinction explains §9. Mowing removes the contaminated tissue; waiting does not, because what remains is inside the flower rather than on it.

18.2 Why this changes the advice about timing

Two different timing rules follow from the two routes. Against contact hazard, delaying access to a treated area for a couple of days materially reduces risk. Against dietary hazard, delay accomplishes little because the residue is being served in nectar for as long as the contaminated flowers persist.

An operator who says it is safe once it dries is applying the first rule to a situation governed by the second. We would put that as the single most common error in how this is explained to clients, and flag it as our judgement.

18.3 The compound dependence

The 48 hour figure concerns one compound in one study.⁶ Residual persistence varies by active, by formulation and by surface, which this journal established at length for structural substrates, and there is no reason to expect a single number to transfer.

19. The reported kills

What is on record.

A 2015 report found seventeen reported pollinator kills over a seven-year period related to the use of one insecticide, mostly in urban areas or on ornamental plants.⁸

19.1 How to read a small number

Seventeen reported incidents in seven years is a small figure, and there are two readings. Either kills are rare, or they are rarely identified, attributed and reported.

A pollinator kill requires someone to notice dead bees, connect them to an application, know that a reporting route exists, and use it. For a wild bee population with no keeper, none of those steps occurs. We would expect substantial under-ascertainment and flag that as reasoning.

19.2 The location detail

That the reported kills were mostly in urban areas or on ornamental plants⁸ is the part relevant to this trade. The recorded incidents are not predominantly agricultural.

20. What an operator should do

The guidance is specific and practical. With perimeter sprays, care needs to be made to avoid bee-attractive plants. If that is impossible without compromising the treatment, consider covering these blooming plants during the spray, or spraying when the plants have no blooms on them.²

The highest risk for pollinator exposure is when a toxic pesticide is applied to an attractive plant in full bloom.²

20.1 The list we would work from

Interior work is not the issue. Indoor uses are assumed not to present reasonable potential for bee exposure.⁷

Look at the plants before the sprayer comes out. Bloom presence is the single variable.²

Mow or remove blooms where you can. The experiment found the hazard went with them.¹

Cover what cannot be removed. Named in the extension guidance.²

Product choice matters. Two products on the same turf produced opposite outcomes.¹

Do not read foraging activity as safety. Bees did not avoid treated blooms.¹

Treat barrier spraying as the highest-exposure service offered. It is named specifically in the assessment.⁴

Remember systemics reach flowers that were not open yet. Soil and trunk applications move into the plant.⁸

Measure the dose. Rate and frequency are named as the two application concerns.⁸

Dry is not the same as safe. Contact hazard falls with time; dietary hazard does not.⁶

21. The householder problem

The larger share of the exposure may not be professional at all.

Surveys indicate that pesticides, most commonly insecticides, are stored in nearly all residential homes, and that while most home pesticide users read labels, the majority do not measure their pesticide applications precisely, and many dispose of unused pesticide improperly.⁹

21.1 What that implies

A licensed applicator is trained, measures, and is bound by the label. A household applying an over-the-counter product to a flowering shrub is doing none of those reliably.

We are wary of this argument because it is convenient for us, and we would not use it to deflect from §11. Both can be true: professional barrier spraying is a named risk, and unmeasured domestic application is widespread.

21.2 The useful role

A technician on a property is in a position to say which plants matter and when not to spray, including about the products the householder applies themselves. That advice costs nothing and is not currently part of most services.

It also has a second benefit worth naming. A household told which plants matter and when not to spray is less likely to apply an unmeasured product themselves, which is the exposure route §21.1 identifies as widespread and unmanaged. Advice given during a visit reaches the applications made between visits, and those are the ones nobody is supervising.

22. Limitations and open questions

The lawn experiment is one study on one bee species. Bombus impatiens, two products, one turf system.¹ It is well designed and it is not a literature.

The barrier spray work is an initial assessment using calculated risk quotients. Set out in §12.1. It models acute contact hazard rather than observing outcomes.⁴

The drift figure is agricultural. Stated in §17.1.

Regulatory material is United States. Label requirements, the bee advisory box and the risk assessment guidance are from a different regulatory system than the one governing this company, and Canadian requirements differ.⁵⁶⁷

We have not addressed Canadian or Manitoba pollinator data. We located none on urban pesticide exposure here, and the species composition of prairie urban pollinator communities is not something we can speak to.

Toxicity data covers few species. Stated in §13, by the sources themselves.³⁴

Sections 4.1, 10.1, 17.1, 19.1 and 21.1 are our reasoning. The ground-nesting soil overlap, the cost-of-the-fix argument, the urban drift translation, the under-ascertainment argument and the comparison with domestic application are ours rather than sourced findings.

Our commercial position. This company provides mosquito control and applies insecticide outdoors, including perimeter treatments. An article stating that barrier spraying is the highest-exposure service in the trade, and that a bloom check should precede every exterior application, is an article constraining our own work. We think the constraint is correct and cheap.

23. Conclusion

Indoor treatment is assumed not to present reasonable potential for bee exposure.⁷ Outdoor spray is assumed to present it where it reaches or drifts onto attractive plants while bees are foraging.⁷ Between those two sentences sits everything this trade does outside a building.

Bumble bee colonies foraging on clover blooms treated at label rate showed delayed weight gain and produced no new queens, the bees did not avoid the treated blooms, and the nectar of directly contaminated flowers held 171 parts per billion of the active.¹ A 2025 assessment named barrier sprays performed by private companies as likely posing significant risk to pollinators.⁴ The industry does not get to treat this as somebody else's argument.

What makes it tractable is the same experiment. Once the blooms present at treatment had been mown off and new flowers had grown on the same treated ground, neither product harmed the colonies.¹ The hazard travelled with the flowers. Which means the remedy is a technician looking at what is in bloom before the sprayer comes off the truck, and either mowing it, covering it, moving the date, or choosing a different product. None of that is expensive, none of it requires a regulation that does not already exist, and a hazard avoidable at that price is one there is no good reason to keep causing.

References

1. Larson, J.L., Redmond, C.T. and Potter, D.A. (2013). Assessing Insecticide Hazard to Bumble Bees Foraging on Flowering Weeds in Treated Lawns. PLOS ONE. doi:10.1371/journal.pone.0066375. Principal experimental source. Used for the observation that despite label precautions not to apply them to blooming plants, neonicotinoids and other residual systemic insecticides may be applied for preventive control of lawn insect pests when spring-flowering weeds are present, and that while dietary exposure to neonicotinoids adversely affects bees the extent of hazard from field usage is controversial; for the design in which colonies of Bombus impatiens were exposed to turf with blooming white clover treated with clothianidin or chlorantraniliprole at label rate and lightly irrigated, with colonies confined to forage for six days after residues had dried and then moved to a non-treated rural site; for the finding that colonies exposed to clothianidin-treated weedy turf had delayed weight gain and produced no new queens whereas those exposed to chlorantraniliprole developed normally compared with controls; for the finding that neither bumble bees nor honey bees avoided foraging on treated white clover in open plots; for the measurement of 171 plus or minus 44 parts per billion clothianidin in nectar from clover blooms directly contaminated by spray residues; for the finding that neither insecticide adversely impacted bee colonies confined on the treated turf after it had been mown to remove clover blooms present at the time of treatment and new blooms had formed; and for the authors' conclusion that the results validate label precautionary statements not to apply neonicotinoids to blooming plants. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680470/
2. Are my pesticides harmful to pollinators? Oregon State University Extension Service. Extension source. Used for the statements that toxicity is not the only factor resulting in the death of bees but also whether bees are likely to be exposed; that the highest risk for pollinator exposure is when a toxic pesticide is applied to an attractive plant in full bloom; that an insecticide treatment applied in a cockroach bait around the interior of a home will be of very little risk to bees and other beneficial insects; and that with perimeter sprays care needs to be made to avoid bee-attractive plants, with the options of covering blooming plants during the spray or spraying when the plants have no blooms on them where avoidance is impossible without compromising the treatment. https://extension.oregonstate.edu/ask-extension/featured/are-my-pesticides-harmful-pollinators
3. Enhancing urban and suburban landscapes to protect pollinators, EM 9289. Oregon State University Extension Service. Extension source. Used for the four identified exposure routes, comprising direct contact with pesticides or residues that remain active on foliage and flowers, presence in nectar and pollen for systemic treatments drawn up through the plant's vascular system, pesticide drift into areas where bees are foraging, nesting or gathering nesting material, and pesticide runoff contaminating water that bees forage on or the nesting beds of ground-nesting bees; for the statement that scientists do not yet know the effect of long-term low-dose exposure, known as chronic toxicity, and do not know much about the acute toxicity of pesticides on pollinating insects outside of honey bees, alfalfa leafcutting bees and some bumble bees; for the statement that pollinators are susceptible to pesticides used in agriculture, forestry, mosquito control and landscape management; and for the observation that while few herbicides are toxic to insect pollinators, many kill plants that provide nectar and pollen for bees. https://extension.oregonstate.edu/catalog/em-9289-enhancing-urban-suburban-landscapes-protect-pollinators
4. An initial assessment of risk to pollinators from mosquito control in residential settings. Stacks Journal, 2025. Used for the conclusion that on a site by site basis, residential mosquito sprays, in particular barrier sprays performed by private companies, likely pose a significant risk to pollinators; for the method of calculating risk quotients for specific pyrethroids and three species of butterflies, finding levels tied to moderate to high risk in many yards; for the statement that calculations utilised acute contact LD50 values to investigate acute risk to honey bees and butterfly caterpillars coated by insecticides when the sprays occurred; for the observation that most insect populations are not monitored so there are potentially other declining taxa present in yards treated with mosquito sprays; and for the point that site level management including planting a diversity of flowering plants can help counter the landscape-wide impact of urbanisation, but that even when habitat is present pollinators and other beneficial insects can still be negatively impacted by pesticide use, with background contamination detected in urban greenspaces including natural areas, community gardens and yards. https://stacksjournal.org/article/anderson-25013/
5. Minimizing Honey Bee Exposure to Pesticides, ENY-162/IN1027. University of Florida Institute of Food and Agricultural Sciences Extension. Extension source, United States regulatory context. Used for the statement that additional Pollinator Protection Labeling is required for pesticides including all neonicotinoid class insecticides registered for foliar use outdoors, with labels from 2014 required to have a pollinator protection portion including a bee advisory box giving general information on routes of exposure and spray drift precautions and a Directions for Use portion providing mitigation options; and for the statement that it is important to remember the purpose of insecticides, which is that they kill insects. https://ask.ifas.ufl.edu/publication/IN1027
6. Protecting Pollinators through the Pesticide Label. North Carolina Department of Agriculture and Consumer Services, Structural Pest Control and Pesticides Division. Regulatory guidance, United States. Used for the description of advisory language covering different routes of exposure for bees, best management practices to reduce exposure including reducing drift, and information about how to report bee kills; for the statement that bees exposed to spray drift extend 1000 feet from the edge of the treated field; for the finding that for one neonicotinoid compound all crops and application methods where on-field exposure was expected produced exposure concentrations exceeding the risk levels of concern for bees, with off-field spray drift assessment indicating risk from all foliar uses even where on-field exposure was not expected, and refined analysis showing the compound could adversely affect bee larvae from chronic oral exposure; and for the residual toxicity study indicating that aged residues at 48 hours did not cause significant increases in bee mortality by contact, with the primary post-application risk concern being dietary routes of exposure. https://www.ncagr.gov/divisions/structural-pest-control-and-pesticides/pollinator/protecting-pollinators-through-the-pesticide-label-pdf/open
7. Guidance for Assessing Pesticide Risks to Bees. United States Environmental Protection Agency, Office of Pesticide Programs. Regulatory guidance. Used for the statements that outdoor spray applications are generally assumed to have a reasonable potential to result in exposure of adult bees and their brood if applied to pollinator attractive crops or drifting to pollinator attractive plants during periods when bees are likely to be foraging; that exposure to bee brood and other castes in hives is expected when exposure to foraging bees is identified, as foragers bring residues back to the hive; that pre-bloom foliar application to pollinator attractive crops may also result in exposure if the pesticide is persistent and translocates to pollen and nectar; and that in contrast indoor uses are generally assumed not to have a reasonable potential for exposure of bees to pesticides, with exceptions such as greenhouses where bees are used. https://www.epa.gov/sites/default/files/2014-06/documents/pollinator_risk_assessment_guidance_06_19_14.pdf
8. Protecting Pollinators in Urban Areas: Reducing Hazards from Pesticide Use. Alabama Cooperative Extension System. Extension source. Used for the statement that a 2015 report by the Environmental Protection Agency found seventeen reported pollinator kills over a seven-year period related to the use of the insecticide, mostly in urban areas or on ornamental plants; for the statement that insecticides applied by trunk injection, soil application or spray are designed to remain active on leaves, stems or flowers and that these residues can be hazardous to pollinators; and for the identification of the two precautions on the bee advisory box as direct contact with foliar residues and ingestion of residues in pollen and nectar, with the note that systemic insecticides applied to soil or by trunk injection move into the plant and possibly into the flowers, making precise rate and frequency of application crucial. https://www.aces.edu/blog/topics/bees-pollinators/protecting-pollinators-in-urban-areas-reducing-hazards-from-pesticide-use/
9. Pesticides and pollinators: A socioecological synthesis. Science of the Total Environment. doi:10.1016/j.scitotenv.2019.01.016. Used for the report that pyrethroid insecticides associated with mosquito abatement were found to be a major contaminant of pollen collected by honey bees in Indiana, attributed to Long and Krupke (2016), and that a large bee-kill occurred in South Carolina in 2016 after an aerial application of an organophosphate insecticide; and for the survey findings from California and Minnesota indicating that pesticides, most commonly insecticides, are stored in nearly all residential homes, and that while most home pesticide users read labels, the majority do not measure their pesticide applications precisely and many dispose of unused pesticide improperly. https://www.sciencedirect.com/science/article/pii/S0048969719300166