Summary
Borax and boric acid do kill fleas. However, these borates only affects the larval stage. Flea larvae must ingest the borate compound to die. The treatment, such as Fleabusters RX, should be applied in the environment to flea hot-spots in order to give it the best chance to mix with larval food. Studies have shown that Fleabusters can suppress 98-100% of flea larvae. It will remain active for up to 18 months, continuing to kill 75% of flea larvae.
Details
Borate-containing Compounds
Borates are naturally occurring compounds that contain the element boron. Numerous pesticide products contain borate compounds. Common ingredients are sodium borate (borax), sodium polyborate, and boric acid (orthoboric acid). Fleabusters RX powder is among the most notable brands in flea control.
In 1948, borates were first registered as pesticides in the U.S. Popularity quickly rose as they were being recommended as the least toxic pesticides for killing insects. Boric acid and its salts were first used to combat cockroaches. Now they’re commonly used against fleas, termites, cockroaches, and wood-boring insects.
Borate-containing compounds have many benefits over traditional insecticides. They have low toxicity to humans and mammals. They last a long time, have no odor, and are relatively inexpensive. Insects haven’t developed resistance to borates. Also, insects aren’t repelled, so the compounds can be used in baits.
Mode of Action
Boric acid and derivatives are metabolically inactive. They kill insects either by acting as a stomach poison, or as a contact abrasive which erodes and absorbs insects’ outer layer of wax, causing them to desiccate. With fleas, the larvae must ingest the compound. There’s no contact toxicity and desiccation with fleas.
Only the larval stage is killed by borates. And, as an intestinal poison, only actively feeding larvae are vulnerable. Like eggs and pupae, non-feeding pre-pupae are unaffected. Still, boric acid and related compounds can constitute a portion of an integrated flea management program. Larvicides suppress immature fleas before they reach the biting adult stage.
Efficacy
Larval Mortality
Powders
Borates are effective flea larvicides. They can cause 100% mortality of larvae. One of the first studies applied borax to dog runs, and saw a noticeable reduction of flea counts on animals confined to the runs. Since then, multiple studies have tested boric acid and related compounds against flea larvae. Regardless of the compound or application rate, borates have proven to be highly effective against flea larvae, ultimately preventing cocoon formation and adult emergence. In 4 to 6 weeks, complete flea control can be obtained.
Much of the research has been limited to the Fleabusters Rx powder. It has demonstrated over 99% suppression of flea development in treated carpets. There was no significant difference found between light, medium, and heavy application rates. On day 3, reduction of flea larvae was 77.7% for the light treatment, 83.3% for the medium treatment, and 97.6% for the heavy treatment. By day 21, all application rates saw a 98-100% reduction in fleas.
Aqueous Solutions
Aqueous solutions of 2.5% disodium octaborate tetrahydrate, applied with carpet cleaning equipment, provided at least 60 days of control of all larval stages. Similarly, 5% and 10% disodium octaborate solutions applied with a standard rental carpet cleaning machine killed over 90% of larvae for at least 56 days. Still, disodium octaborate tetrahydrate is about one-third as active as the powdered boric acid.
Residual Activity
Borates remain active in the environment much longer than traditional insecticides. Residual activity should persist for over a year, even with regular cleaning and vacuuming. Studies done on Fleabusters RX show that it can suppress 75% of flea development in carpets for 18 months, as long as it doesn’t get wet.
Unlike pesticides composed of complex molecules, boric acid and derivatives don’t break down or degrade in air. In water, they rapidly transform to borates, the naturally occurring form of boron. No further degradation is possible.
Wet Cleaning Reduces Efficacy
Water changes the chemical characteristics of boric acid and renders it less effective. To preserve residual activity, it’s advised not to do any wet cleaning in the environment, such as carpet shampooing or mopping. This disadvantage isn’t limited to borates, as most insecticides will lose activity with wet cleaning methods. If carpets aren’t wet cleaned, some companies guarantee that borate treatments will remain active for one year.
Product Differences & Unsupported Claims
How effective a particular borate product is depends upon the particle size and the concentration in the carpet. The variation of chemical and physical properties of the assorted products makes generalizations about activity difficult. Products not evaluated by scientific study often make comparable claims to Fleabusters RX. Additionally, only a few borate-containing products are EPA approved for broadcast application. Others are approved for “crack and crevice” treatment which limits their usefulness for flea control.
Application
Indoor Use
Borates are used for indoor environmental flea control. Outdoors, exposure to moisture and water will make them less effective. Some pet-owners have used borate compounds outdoors, but there isn’t information on its effectiveness. One study suggests outdoor use may be feasible.
Where to Apply
Borates only work when larvae ingest them. Thus, it’s important to apply the dust in flea breeding grounds. When the powder mixes with the larval food supply, it’ll have the highest chance of being ingested, and then be an effective control method.
Boric acid and borate compounds can be used throughout homes, applied on carpets, rugs, hard floors, pet beds, cat trees, cupboards, and furnishings. Successful control depends on thoroughness of application. Give special attention to areas favored by pets. As a warning, with time, boric acid may damage carpet fabric or upholstery.
Borates are most effective in carpeted environments. Carpets can be effectively treated alone with boric acid or borax, or in combination with diatomaceous earth. The powder is worked into the nap of the carpet and then thoroughly vacuumed.
Powder or Liquid
Borates have been tested in liquid and dust preparations. The efficacy and lasting effect of powder is far superior to liquids.
Professional Application
Application can be done by pet-owners. Professional services are available to provide maximal efficacy.
Safety
Borates are naturally-occurring. As biorational insecticides, they’re relatively non-toxic to people with few environmental side-effects. They don’t engender the same concerns as synthetic pesticides. Borate pesticides are an attractive choice for use in high contact areas, such as on carpeting and furniture. Those looking for “natural” insecticides are especially drawn to borates.
Most safety concerns of borates arise from unproven relationships to medical problems. Calls to the National Animal Poison Control Center did not confirm any specific cause of symptoms or relationship to borates. Miscalculating application rates can sometimes result in safety concerns. And unfounded fears have come from borate producers withdrawing from EPA approval.
Adult Mammalian Toxicity
Borates have a low toxicity to humans and other mammals. Adults are resistant to toxic effects. In prolonged feeding trials, both dogs and rats had no toxic effect. Cats living in sodium polyborate treated habitats for 5 months did not uncover any associated signs of toxicity. Borates are approved for inside broadcast application in California, which indicates a safe product based upon this state’s high safety standards.
Although boric acid is relatively safe to humans and other mammals, it can be harmful if accidentally ingested. It should be kept away from food, children, and pets. Care must be taken not to breathe in the dust when you apply it. Symptoms of exposure to boric acid dust include difficult breathing, headache, lethargy, nausea, coughing, and wheezing. Irritation of the nose, throat, or eyes can occur if small amounts of boron are breathed in.
Young Mammalian Toxicity
Young animals, particularly human newborns and infants, are very susceptible to boric acid toxicity. Toxicity can occur secondary to acute or chronic ingestion, or transdermal absorption through damaged skin. Fatalities have occurred via acute and chronic exposures. Don’t use or store boric acid in areas where children have easy access to the powder.
Reproductive Toxicity
The most significant health concerns associated with exposure to boric acid and borates are their ability to reduce successful reproduction. Boric acid can damage sperm, increase the frequency of miscarriages, reduced birth weight, and cause a variety of birth defects. In general, these effects occurred during relatively high exposures.
Not a Carcinogen
Boric acid is classified as a “Group E” carcinogen. This means that it shows no evidence of causing cancer.
Fish
Fish need boron in order to develop and grow normally. However, high concentrations can be toxic.
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