Used Since 1889, Mechanism Still Open: Boric Acid, Borates, and the Solubility Paradox

1. Introduction: the oldest active in the van

Almost every pest control vehicle carries a borate product. It is cheap, it has a long history, and most technicians could not tell you how it kills an insect. Neither, it turns out, can the literature.

1.1 And the modern position

A regulatory database lists the mode as stomach poison and as an antifeed for insects distrupting insect enzyme & digestive systems, with multi-site activity.⁴

Multi-site activity is an honest way of saying several things at once, and possibly a way of saying that nobody has isolated one.

2. What the family contains

Terminology first, because the names are used loosely in the trade.

Boric acid and its sodium borate salts are active ingredients in pesticide products used as insecticides, acaricides, algaecides, herbicides, fungicides and as wood preservatives. They exist naturally in rocks, soil, plants and water as forms of the naturally occurring element boron. The borate salts include sodium tetraborate, disodium octaborate and sodium metaborate, and both sodium tetraborate and disodium octaborate occur in several hydration states. Sodium tetraborate decahydrate is also known as borax.²

2.1 Boric acid is not borax

A retail source states plainly that boric acid is not the same as borax: both are boron compounds, but boric acid is the more refined form used in insecticidal baits.⁹

2.2 And the one you meet in structural work

Disodium octaborate tetrahydrate, abbreviated to DOT, which is the wood treatment. A county health department factsheet describes it as killing and preventing termites, carpenter ants, wood boring beetles and other insects and acting as a stomach poison against ants, beetles, cockroaches, silverfish, and termites.⁷

3. The history

Longer than almost anything else in current use.

A trade account records that one of the earliest mentions of borates in pest control goes back to the late 1800s, in which borax was recommended as a bait toxicant for controlling cockroaches and ants, citing an 1889 source.³

Boric acid was first registered as a pesticide in the U.S. in 1948, and at the time of a regulatory review 189 pesticide products were registered which contain boric acid or its salts.¹ Registration and re-registration are dated to 1948 and 1993 respectively.²

3.1 Fifty-nine years of use before registration

Which is a reminder of what the regulatory era replaced. This journal's article on the origins of pesticide regulation described a world in which products were used first and assessed later, and this is a surviving example of exactly that sequence.

4. The registered uses

The breadth is unusual and worth setting out.

Pesticide products containing boric acid and its sodium salts are registered in the U.S. for use as insecticides, fungicides and herbicides. As insecticides, some act as stomach poisons in ants, cockroaches, silverfish and termites, while others abrade the exoskeletons of insects. As herbicides, some cause desiccation or interrupt photosynthesis in plants, while others suppress algae in swimming pools and sewage systems. As fungicides, several are wood preservatives which control decay-producing fungi in lumber and timber products.¹

4.1 One element, four pest categories

Insects, plants, algae and fungi. A regulatory database adds biocide, wood preservative, embalming fluid, slimicide, disinfectant, algicide and agricultural fertiliser to the list.⁴

An active ingredient that is also a fertiliser is doing something unusual, and §20 returns to what that means for its toxicology.

4.2 What a fertiliser tells you

Boron is a plant micronutrient, required in small amounts and toxic in larger ones. The same compound appears as a fertiliser and as a herbicide⁴ because the only difference is the dose.

That is the clearest possible illustration of the principle, and it is worth holding when reading §20. A compound with no dose-independent hazard is not the same thing as a compound with no hazard.

4.3 The structural pest list

An extension database gives the targets as ants, bed bugs, carpenter ants, carpenter bees, carpet beetles, cockroaches, drywood termites, silverfish and firebrats, subterranean and other termites, wood-boring beetles in homes.⁵

That is most of the structural pest list, from one active, which should prompt some suspicion about how specific the mechanism can be.

A compound that kills ants, beetles, roaches, termites, bed bugs and silverfish is either acting on something all insects share or acting by several routes at once. The multi-site description in §7 is the second answer.

5. The mode of action problem

Collecting what the sources actually claim.

The candidates are not mutually exclusive and the sources do not agree on their relative importance. Sections 6 to 10 take them in turn and §11 removes one that does not belong.

6. Stomach poison

The claim every source makes.

It is named as a stomach poison in ants, cockroaches, silverfish and termites,¹ as a stomach poison against ants, beetles, cockroaches, silverfish, and termites,⁷ and as a stomach poison that may also have toxic effects on insect's nervous systems.⁵

6.1 The route of entry

A retail source describes it as a slow-acting stomach toxicant once ingested during grooming.⁹

Grooming is the important word. An insect that walks through a dust does not need to eat bait; it cleans the particles off itself and swallows them. That is why a dust in a void works on a species that never encounters a bait station.

6.2 Why slow action is a feature

This journal's article on horizontal transfer and delayed action explained why a toxicant that kills immediately performs worse in a social insect than one that does not. The same logic applies to a grooming-ingestion route: the insect must survive long enough to return to harbourage and to groom.

7. Enzymes and multi-site activity

The second description, which is more specific and less common.

A pesticide properties database gives the mode as stomach poison and antifeed for insects distrupting insect enzyme & digestive systems, with multi-site activity.⁴

7.1 What multi-site implies for resistance

A compound acting at one target site is vulnerable to a single point mutation, which is the story of most of the resistance this journal has written about. A compound acting at many sites is much harder to evolve around.

That would predict low resistance development to borates, and we found no reports of borate resistance in structural pests in this search. We flag that as an absence in our search rather than an established fact.

8. The gut pH hypothesis

A specific mechanism proposed for wood-boring insects, from a patent and therefore flagged as commercial advocacy.

The patent describes a related borate from which ammonia is also liberated in the gut of wood decaying insects, where ammonia neutralizes the acidity (pH 5.0-6.0) of the content of the insect's gut and thus inhibits the activity of cellulase enzyme which is essential for the acid catalyzed hydrolysis of cellulose to glucose in wood boring insects.⁸

8.1 What it describes

Starvation rather than poisoning. The insect cannot digest wood because the enzyme that breaks cellulose down requires an acid gut.

8.2 Its limits

It is specific to the ammonium salt described in that patent and to insects digesting cellulose, so it cannot explain cockroach mortality. And it appears in a document written to argue for the claimed invention.⁸

We include it because it is the only mechanistic hypothesis with an actual biochemical pathway that we located, and because the same document states flatly that the mode of action of boric acid itself is unknown.⁸

9. The nervous system claim

Briefly, because the evidence offered is thin.

An extension database states that borate may also have toxic effects on insect's nervous systems.⁵

9.1 May

No mechanism, no target, no citation in the entry we read. We report it as a claim in a reputable source and note that it is unsupported there.

9.2 Why we include it at all

Because it illustrates the state of this literature. An extension database serving practitioners offers a possible nervous system effect without a reference, and that is the level of certainty available for an active in use since the 1880s.

Contrast this journal's articles on receptor-level work in repellents and on the sequence selectivity of an RNA-based pesticide, where the mechanism is specified to the molecule. The gap in rigour is a hundred and thirty years wide and runs in the direction you would not expect.

10. The abrasion claim

The contested one.

A regulator states that among insecticidal borate products, others abrade the exoskeletons of insects.¹ An extension database says some products may be abrasive and scratch insect's exoskeletons, causing them to dry out.⁵

An industry association argues the point with a number: the Mohs hardness of boric acid is 3.0 on a scale of 1-10 with 10 classified as a diamond. Thus boric acid and some hydrated sodium borates are also abrasive to the insect's exoskeleton which results in another way of insecticidal mortality.⁶

10.1 The source is selling borates

An industry association making the case for its own product category, flagged accordingly.⁶ A hardness of 3.0 is comparable to a copper coin and it is not obvious that this settles the question either way.

10.2 The distinction that gets lost

Abrasion and sorption are different mechanisms. A hard particle can scratch a cuticle; a porous particle can absorb its wax. Boric acid is claimed for the first and, per §11, disclaimed for the second.

Both are frequently summarised in the trade as drying the insect out, which conflates them.

11. It is not a desiccant

The correction, and it applies to a claim this journal has encountered repeatedly.

A trade technical article states: boric acid is mistakenly considered by some references as a desiccant dust. However, scientific evidence suggests boric acid's sorptive property is negligible when compared to true desiccant dusts, such as silica gel or diatomaceous earth.³

11.1 What a real desiccant does

This journal's article on desiccant dusts described the mechanism: silica gel and diatomaceous earth adsorb the epicuticular wax layer, after which the insect loses water it cannot replace. That is sorption, and it is a measurable physical property.

11.2 Boric acid does not do that

Its sorptive property is described as negligible by comparison.³

So the two dusts a technician might reach for in the same situation are not two versions of one thing. They have different mechanisms, different speeds and different failure modes, and this correction should be read alongside our desiccant article.

12. Why the correction matters

Not pedantry, because the mechanism determines the deployment.

A desiccant works on contact. The insect walks through and begins losing water immediately, without needing to ingest anything.

A stomach poison requires ingestion. Which for a dust means grooming, which requires the insect to survive the encounter and to groom afterwards.⁹

12.1 The practical difference

A species that grooms fastidiously is well suited to a borate dust. A species that does not, or one whose behaviour has been altered, is less so. Our article on behavioural resistance in German cockroaches described how readily behaviour changes under selection.

12.2 And the humidity difference

A desiccant's performance depends on ambient humidity, because it is competing with the air for the insect's water, which our desiccant article set out. A stomach poison does not have that dependency in the same way.

So a contractor who believes boric acid is a desiccant will expect the wrong humidity behaviour from it. That is our point and it is the reason for this section.

13. Why it works anyway

The most useful sentence in the whole search, from the industry source.

In the case of the cockroach, lack of repellency of boric acid plus its electrostatic tendency to stick to the insect's body outweighs its relatively low toxicity by comparison with certain organic insecticides.⁶

13.1 Read that as an admission

An association promoting borates states that its toxicity is relatively low compared with organic insecticides, and that what compensates is that insects do not avoid it and it clings to them.⁶

13.2 Which is the recurring finding of this journal

Our articles on bait aversion, on rodent neophobia, on glucose aversion and on repellency have all reached the same conclusion from different directions: what an insect or rodent will accept matters more than what would kill it if accepted.

Boric acid is the clearest case. A weak poison that nothing avoids outperforms a strong poison that everything does.

13.3 The electrostatic point

Particle adhesion determines dose. A dust that clings delivers more material per encounter than one that does not, which is a formulation property rather than a chemical one.

It also explains why particle size and grade matter in a product that is chemically identical across suppliers, and why a technical grade sold for another purpose is not automatically the same product as a registered dust.

13.4 The larval note

The same source adds that in certain other insect species, the borate acts against the larval stage.⁶

Stage-specific activity is worth knowing because a treatment that kills larvae and spares adults produces a delayed decline rather than an immediate one, which is how our article on insect growth regulators described a related pattern.

14. The concentration that works in wood

The number from §1, and it is a small one.

Boric acid is toxic to insects in very low concentrations (0.05-0.2%) in wood.⁸

14.1 Two parts in a thousand at the high end

Which is why borate wood treatment is economically viable at building scale. A timber frame does not need to be saturated.

14.2 And why penetration is the whole problem

If the effective concentration is that low, the constraint is not how much you apply but whether it reaches the depth where insects feed. Section 15 is about the property that solves that.

15. The solubility paradox

The central engineering fact about this chemistry.

Borates are water soluble.⁶ That solubility is how a surface-applied solution diffuses into timber rather than sitting on it, which is what makes a borate a treatment rather than a coating.

15.1 And the same property removes it

A factsheet quotes a reference stating that borates do not degrade but complex with organic matter and sod mineral surfaces and can be altered by water leaching and pH changes.⁷

15.2 The paradox stated

Water carries the treatment in and water carries it out. The property that makes borates uniquely good at treating wood in place is the property that makes them unsuitable wherever the wood gets wet.

We have not found a source stating it that way and we offer it as our formulation.

16. Leaching and where it matters

Following that to the practical consequence.

Decay fungi require moisture, which our article on wood decay and moisture thresholds set out in detail. So does subterranean termite activity, which our termite articles covered.

16.1 The awkward alignment

The wood that most needs preserving is the wood most exposed to the water that removes the preservative. Sill plates, crawl space framing, exterior-adjacent members and anything near a plumbing failure.

That is our inference from the leaching statement and from the moisture requirements.⁷

16.2 Which defines the correct application

Borate treatment of dry, protected, interior framing that is expected to stay dry. Not ground contact, not exterior exposure, not as a substitute for fixing the moisture problem that created the risk.

16.3 Which also explains a common sales claim

Borate wood treatments are marketed as permanent, on the basis that boron does not degrade.⁷ That is true and incomplete. It does not degrade and it does move, so permanence holds only where water does not reach it.

16.4 The persistence claim

The same factsheet notes that disodium octaborate tetrahydrate and its breakdown chemicals are considered persistent but have not been identified as a concern for groundwater.⁷

Persistent and mobile are different properties. Boron does not break down, and in wet conditions it moves.

17. Moisture ruins the dust too

The same property, in the other formulation.

However if these dry refined borates (particularly powders) come in contact with water, their effectiveness as an abrasive can be reduced due to caking of the finished product since borates are water soluble.⁶

17.1 Which is a field observation everybody has made

Boric acid dust in a damp void cakes into a crust. A caked dust is not picked up by a passing insect and is not groomed off, so the ingestion route in §6 closes.

17.2 The application rule that follows

Dry voids, thin layers, and not in locations subject to condensation or moisture. Our article on substrate effects and residual efficacy made a related point about porous surfaces absorbing liquid formulations, and this is the dust equivalent.

18. The sublethal allergen finding

A reference we encountered in a citation list and which deserves its own section.

A technical factsheet's reference list includes a 2005 allergy journal paper whose title is Sub-lethal exposure of cockroaches to boric acid pesticide contributes to increased Bla g 2 excretion.²

18.1 What we have and do not have

We have the title and the journal from a reference list. We have not read the paper, do not know the exposure levels or the effect size, and are reporting a citation rather than a finding.²

18.2 Why it is worth reporting anyway

Because the named allergen is one of the principal cockroach allergens, and this journal's articles on cockroach allergen and childhood asthma and on allergen intervention trials both established that this protein is the health endpoint that matters in an infested home.

A treatment that reduces cockroach numbers while raising allergen excretion per surviving cockroach has an ambiguous effect on the outcome anybody actually cares about.

19. Why that changes the calculus

Connecting it to the rest of this journal's work on sublethal exposure.

Our article on resistance reversion described sublethal dosing of rodents producing raised tolerance across generations, and our article on synergists described metabolic responses to sublethal exposure. The general principle is that a dose below the lethal threshold is not a small version of a lethal dose. It is a different event with its own consequences.

19.1 The specific warning here

Boric acid is slow-acting.⁹ Slow action means a window in which exposed insects are alive and exposed, which is precisely the sublethal condition the cited paper concerns.²

19.2 What we take from it

That in a household with a diagnosed cockroach allergy, a thorough treatment matters more than it does elsewhere, and a partial one may be worse than a different approach. That is our reading of a citation we have not read, and it should be weighted accordingly.

It also argues for the allergen removal step that this journal's intervention articles found to be the part most often skipped. Killing the cockroaches does not remove the protein they have already deposited.

20. The toxicity question

Because boric acid has a reputation for safety that is partly earned and partly not.

A factsheet states that disodium octaborate tetrahydrate's toxicity is based on its boron content, that boron is generally considered low in toxicity due to its prevalence in the environment and people's ingestion of boron daily, but that like most pesticide ingredients, it can be used in applications that can create an exposure of concern and that the risks associated with the use of borate products are related to the potential exposure the application can have.⁷

20.1 The classification that surprises people

A European regulatory database lists boric acid against a criterion for pesticide active ingredients that meet the criteria of reproductive toxicity Categories 1A and 1B of the Globally Harmonized System, with the corresponding hazard classification.⁴

20.2 Both things are true

An element we consume daily in food and water, and a reproductive toxicity classification in a major regulatory system. The dose and the route do all the work, as they do for most things.

We raise it because the trade shorthand for borates is safe, and because a technician spreading a dust in an occupied home should know which hazard class the product sits in.

20.3 The wildlife entries

The same reference list contains papers on toxic effects of boron on mallard reproduction and effects of boron on growth and physiology in mallard ducklings.² We note them without having read them.

21. The home-made bait

Because this is the one professional product the public also mixes at home, and our article on consumer pest products examined what that market gets wrong.

A retail source describes a proven DIY bait of 1 part boric acid to 3 parts powdered sugar, bound with just enough water to make a thick paste, with the sugar as attractant.⁹

21.1 The problems with that

The attractant may be the wrong one. Our article on glucose aversion in German cockroaches described a behavioural resistance trait that makes a sugar-based bait actively repellent to some populations.

Water in the mix. Section 17 is about what moisture does to borates.⁶

And the same source says so. It states that this is the published mechanism behind EPA-registered borate bait products and is not a use direction for bulk boric acid, and that registered borate products are formulated and labelled for specific placements and quantities, with the product label, not a general rule of thumb, governing where and how much may be applied.⁹

21.2 Which is correct and worth repeating

This journal's article on the legal force of the label established that applying a pesticide contrary to its directions is not a technicality. Bulk boric acid sold as a chemical is not a registered pest control product and using it as one is a different act from using a registered bait.

22. Where borates are the right choice

The positive case, which is strong.

Dry interior voids. Wall voids, under appliances, in electrical boxes where permitted by label, where a dust can sit undisturbed for a long time.

Species that groom. Cockroaches, silverfish, firebrats and ants, which the sources list as targets.³⁵

Protected structural timber. Where the wood is expected to stay dry and the treatment will not leach, per §16.2.

Where resistance is a concern. Multi-site activity is the opposite of a single target site,⁴ and our rotation and resistance articles explain why that matters.

And where slow action is acceptable. A client who needs a visible result this week is not a candidate.

23. Where they are the wrong one

The limits.

Anywhere damp. Caking, leaching, or both.⁶⁷

Ground contact and exterior timber. Where leaching is continuous.⁷

As a substitute for a moisture repair. Treating wood that is wet without fixing why it is wet treats the symptom and loses the treatment.

Where the client needs speed. A slow stomach poison is the wrong tool for an urgent problem.

And as a visible dust in occupied space. Section 20 and the label both apply, and a dust the occupants can see is a dust in the wrong place.

24. The Manitoba position

Two local notes.

The dry winter helps. Our article on dust mites and humidity established how low indoor relative humidity runs here in winter, and a dry void is where a borate dust performs best.⁶

And the termite question is mostly moot. Borate wood treatment is marketed heavily on termite protection, and our articles on the northern limit of subterranean termites explain why that is a small consideration in most of this province. The beetle and carpenter ant cases are the local ones.

24.1 And the beetle case is the one that matters here

Our article on concealed insect detection described anobiid beetle activity in interior joinery, and dry interior timber is exactly the condition in which a borate treatment holds. That is the local application with the strongest case behind it.

24.2 What we could not find

Any Canadian-specific registration list, any provincial guidance on borate use in structures, and any Manitoba data on borate resistance or efficacy. As elsewhere in this journal, the local evidence base is empty.

25. Limitations and open questions

The source quality is mixed and mostly not primary. A regulator factsheet, a poison information centre factsheet, an extension database, a properties database, a county health department sheet, a trade magazine, an industry association, a patent and a chemical retailer. No peer-reviewed toxicology was read in full.¹⁶⁹

Two sources are selling borates. The industry association and the chemical retailer both have a direct commercial interest, and the abrasion argument and the adhesion argument both come from the first of those.⁶⁹

The patent is advocacy. Its statement that the mode of action is unknown supports its own claimed invention, and its date means the position may have moved since 1989.⁸

The mode of action may now be better characterised. We searched and found contemporary sources still listing several candidates,⁴⁵ but a specialist toxicology literature may have resolved this and we would not know.

The allergen paper was not read. Section 18 reports a title from a reference list, and everything we draw from it in §19 is contingent on a paper we have not seen.²

The regulatory figures are dated. The 189 product count and the review date come from 1993 documents and the current figures will differ.¹

We found no borate resistance reports and cannot conclude there are none. Section 7.1 states this and it bears repeating.

Sections 1.1, 3.1, 6.1, 6.2, 7.1, 10.1, 10.2, 12, 13.1, 13.2, 14, 15.2, 16.1, 16.2, 17.1, 17.2, 19, 21.1, 22, 23 and 24 are our reasoning. The reading of multi-site activity, the grooming route argument, the abrasion assessment, the consequences of the desiccant correction, the interpretation of the adhesion sentence, the solubility paradox as formulated, the leaching alignment argument, the sublethal calculus and the two lists of appropriate and inappropriate use are ours rather than sourced positions.

26. Conclusion

Borax was recommended against cockroaches in 1889, boric acid was registered in 1948, and by 1993 the active sat in 189 products covering insects, fungi, weeds, algae and timber.³¹ A patent from 1989 states that it kills insects at 0.05 to 0.2 per cent in wood and that nobody knows how.⁸ The contemporary sources offer a stomach poison, an antifeedant disrupting enzyme and digestive systems with multi-site activity, a possible nerve effect and an abrasion mechanism, and one trade source removes a fifth candidate by noting that the sorptive property everybody assumes is negligible against a real desiccant.⁴⁵³

What explains its persistence in the trade is not potency. An industry association states that its toxicity is relatively low compared with organic insecticides, and that what compensates is a lack of repellency and an electrostatic tendency to stick.⁶ A weak poison that nothing avoids has beaten strong poisons that everything does, for a hundred and thirty-seven years, which is the same conclusion this journal has reached from baits, from neophobia and from behavioural resistance.

The engineering limit is a single property. Water solubility is what carries a borate into timber at a concentration of two parts in a thousand, and it is what removes it again wherever that timber gets wet, and what cakes a dust into a useless crust in a damp void.⁶⁷ So borates belong in dry places, they are not a substitute for repairing the moisture that created the problem, and a citation we have not read suggests that a sublethal dose may raise the cockroach allergen output that a treatment in an asthma household was meant to reduce.² An active this old should have better answers behind it than this.

References

1. Reregistration Eligibility Document fact sheet for boric acid. United States regulator document dated 1993. Used for the list of sodium salts covered, namely disodium octaborate tetrahydrate, disodium octaborate anhydrous and sodium metaborate; for the use profile stating that products containing boric acid and its sodium salts are registered as insecticides, fungicides and herbicides, that as insecticides some act as stomach poisons in ants, cockroaches, silverfish and termites while others abrade the exoskeletons of insects, that as herbicides some cause desiccation or interrupt photosynthesis in plants while others suppress algae in swimming pools and sewage systems, and that as fungicides several are wood preservatives controlling decay-producing fungi in lumber and timber products; for the statement that these actives are used on several agricultural and many non-agricultural sites including residential, commercial, medical, veterinary, industrial, forestry and food or feed handling areas; and for the statements that boric acid was first registered as a pesticide in 1948 and that 189 pesticide products containing boric acid or its salts were then registered. https://www3.epa.gov/pesticides/chem_search/reg_actions/reregistration/fs_PC-011001_1-Sep-93.pdf
2. Boric Acid Technical Fact Sheet. National pesticide information centre archived factsheet. Used for the statements that boric acid and its sodium borate salts are active ingredients in pesticide products used as insecticides, acaricides, algaecides, herbicides, fungicides and wood preservatives; that they exist naturally in rocks, soil, plants and water as forms of the naturally occurring element boron; that these pesticides were registered for use in 1948 and reregistered in 1993; that the borate salts include sodium tetraborate, disodium octaborate and sodium metaborate, that both of the first two occur in several hydration states, and that sodium tetraborate decahydrate is also known as borax; that uses for individual products vary widely and that the actives are used against insects, spiders, mites, algae, molds, fungi and weeds; and that boric acid acts as a stomach poison while certain hydrated salts are used to inhibit fungal growth by preventing production of reproductive spores. Also cited for three entries appearing in its reference list which we did not read in full: a 2005 allergy journal paper titled Sub-lethal exposure of cockroaches to boric acid pesticide contributes to increased Bla g 2 excretion, and two environmental toxicology papers on toxic effects of boron on mallard reproduction and on effects of boron on growth and physiology in mallard ducklings. https://npic.orst.edu/factsheets/archive/borictech.html
3. The mysterious boric acid and its relatives. Pest management trade magazine technical article. Trade source, cited as attributed material. Used for the statement that boric acid and other boron-containing compounds such as borax and disodium octaborate tetrahydrate, collectively called sodium borate salts, are well known for their insecticidal properties; for the account that one of the earliest mentions of borates in pest control goes back to the late 1800s, when borax was recommended as a bait toxicant for controlling cockroaches and ants, citing an 1889 source; for the statement that boric acid and borates are currently used as active ingredients in many products to control pests in urban and agricultural settings, in formulations including dust as the pure compound, liquid spray, and granular, liquid or gel baits, and that boric acid is sold as a general-use dust for controlling cockroaches, silverfish, firebrats and ants; and for the correction that boric acid is mistakenly considered by some references as a desiccant dust, while scientific evidence suggests its sorptive property is negligible compared with true desiccant dusts such as silica gel or diatomaceous earth. https://www.mypmp.net/the-mysterious-boric-acid-and-its-relatives/
4. Boric acid entry, pesticide properties database maintained by a university agriculture and environment research unit. Used for the description of the compound as a weak acid of boron with antiseptic and insecticidal activity; for the listed targets of cockroaches, ants, silverfish, carpenter ants and termites in domestic, commercial and industrial non-food areas; for the listed functions of biocide, wood preservative, embalming fluid, slimicide, disinfectant, algicide and agricultural fertiliser; for the stated mode of action as stomach poison and as an antifeedant for insects disrupting insect enzyme and digestive systems, with multi-site activity; and for the entry recording the compound against a criterion covering pesticide active ingredients that meet the criteria of reproductive toxicity Categories 1A and 1B of the Globally Harmonized System on Classification and Labelling of Chemicals, with the corresponding hazard classification. https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/2136.htm
5. Boric acid and borate entry, statewide integrated pest management programme pesticide active ingredients database at a state university. Used for the description of the active as a boron-based insecticide acting as a stomach poison that may also have toxic effects on insects' nervous systems, and the note that some products may be abrasive and scratch insects' exoskeletons causing them to dry out; and for the listed pest targets of ants, bed bugs, carpenter ants, carpenter bees, carpet beetles, cockroaches, drywood termites, silverfish and firebrats, subterranean and other termites, and wood-boring beetles in homes. https://ipm.ucanr.edu/home-and-landscape/pesticide-active-ingredients-database/active-ingredient-details/?uaiKey=102
6. Borates in Pesticides. Industry association page for a borate producer. Commercial source advocating for the product category, cited as attributed material. Used for the argument that the Mohs hardness of boric acid is 3.0 on a scale where diamond is 10, and that boric acid and some hydrated sodium borates are therefore abrasive to the insect exoskeleton, giving another route to insecticidal mortality; for the statement that if dry refined borates, particularly powders, come into contact with water their effectiveness as an abrasive can be reduced through caking of the finished product, since borates are water soluble; for the assessment that in the case of the cockroach, lack of repellency of boric acid plus its electrostatic tendency to stick to the insect's body outweighs its relatively low toxicity by comparison with certain organic insecticides; for the note that in certain other insect species the borate acts against the larval stage; and for the list of formulations in which borates are marketed, including liquids, soluble and emulsifiable concentrates, granular products, powders, dusts, pellets, tablets, solids, paste, baits and crystalline rods. http://www.americanborate.com/all-about-borates/borate-applications/borates-in-pesticides/
7. Disodium octaborate tetrahydrate, county health department hazardous substances factsheet. Local government consumer information document. Used for the quoted statement, attributed within it to a further reference, that borates do not degrade but complex with organic matter and soil mineral surfaces and can be altered by water leaching and pH changes; for the note that disodium octaborate tetrahydrate and its breakdown chemicals are considered persistent but have not been identified as a concern for groundwater; for the described uses of killing and preventing termites, carpenter ants, wood boring beetles and other insects, and acting as a stomach poison against ants, beetles, cockroaches, silverfish and termites; and for the toxicological framing that the compound's toxicity is based on its boron content, that boron is generally considered low in toxicity due to its environmental prevalence and daily human ingestion, but that like most pesticide ingredients it can be used in applications creating an exposure of concern, with risks related to the potential exposure the application creates. https://s3.us-west-2.amazonaws.com/thurstoncountywa.gov.if-us-west-2/s3fs-public/2023-01/EH_HW_Health-basic-61-PDF-18_Disodium%20octaborate%20tetrahydrate.pdf
8. Insecticidal composition. United States patent specification. Patent document arguing for its own claimed invention, flagged as commercial advocacy rather than neutral assessment. Used for the statement that boric acid is known to be toxic to insects such as termites, powderpost beetles, black carpet beetles, fire ants, carpenter ants, carpenter bees, cockroaches, silverfish, houseflies and other insects; for the statement that boric acid is toxic to insects in very low concentrations of 0.05 to 0.2 per cent in wood but that its mode of action is unknown; and for the proposed mechanism that ammonia liberated from a related borate in the gut of wood decaying insects neutralises the acidity of the gut contents at pH 5.0 to 6.0 and thereby inhibits the activity of the cellulase enzyme essential for acid catalysed hydrolysis of cellulose to glucose in wood boring insects. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/4873084
9. Boric Acid and Cockroaches: chemistry, grades, safety. Chemical retailer article. Commercial source selling the material discussed, cited as attributed material and treated with corresponding caution. Used for the description of borates as affecting cockroach physiology in two ways, as a slow-acting stomach toxicant once ingested during grooming and as an abrasive that disrupts the waxy epicuticle and accelerates water loss, described there as the published mechanism behind registered borate bait products; for the statement that boric acid is not the same as borax, both being boron compounds but boric acid the more refined form used in insecticidal baits; for the home-made bait described as one part boric acid to three parts powdered sugar bound with just enough water to make a thick paste, with the sugar as attractant; and for the cautions given in the same source that this is not a use direction for bulk boric acid, that registered borate products are formulated and labelled for specific placements and quantities, that the product label rather than a general rule of thumb governs where and how much may be applied, and that such baits should be kept away from children, pets and food preparation surfaces. https://alliancechemical.com/blogs/articles/win-the-war-against-roaches-boric-acid-bait-secrets-revealed