Physical Desiccation | Moisture Management

Diatomaceous earth is a naturally occurring powder that has gained popularity in recent years, particularly in pest control. This fine, powdery substance consists of the fossilized remains of diatoms (microscopic, single-celled aquatic plants). The unique characteristics of diatomaceous earth make it an effective and natural alternative to chemical-based pest control methods in various settings, including homes and gardens.
However, with the rise in popularity of diatomaceous earth comes the question: does it work? To address this question, it is essential to understand how diatomaceous earth functions and what makes it effective against pests. 
Key Takeaways

• Diatomaceous earth's effectiveness is derived from its unique composition, which aids in natural pest control.

• Safety and environmental impact are important factors to consider when evaluating the use of diatomaceous earth in various settings.

• Understanding common uses and applications can provide insight into the true effectiveness of diatomaceous earth.

Diatomaceous earth (DE) is a geological deposit consisting of the fossilised skeletons of numerous species of siliceous marine and fresh water unicellular organisms, particularly diatoms and other algae. Many of these fossilised sedimentary layers originated at least 20 million years ago in the lakes and seas of the Eocene and Miocene epochs. After quarrying, crushing and milling, a fine light dust is obtained, containing porous particles with certain abrasive properties and the ability to absorb lipids to about three or more times the particle mass. Any diatomaceous earth with high oil absorbing capacity is a potential insecticide. Beyond the absorbing capacity, the size of particles, uniformity and shape of the particles, pH, and the purity of formulation affect the compound's insecticidal efficacy. Insecticidal diatomaceous earth should be a highly pure amorphous silica, having particles of equal diameter (< 10 μm), pH<8.5, containing the least possible number of clay particles and less than 1% crystalline silica. The particles of diatomaceous earth are easily picked up by rough bodied insects. The particles damage the cuticle through hydrocarbon absorption and abrasion making the cuticle permeable to water which rapidly leaves the insect's body causing death from desiccation. In this paper the advantages and disadvantages of diatomaceous earth as an insecticide and its scope of use are discussed. Briefly, the description of DE application, the modes of action and its uses are described. Tests results show great variation in physical properties and efficacy against insects among DEs from different geographical locations. Environmental factors affecting efficacy and the potential scope of DE use are discussed.

Diatomaceous earth (DE) and other inert dusts have been used for thousands of years as insecticides. The Chinese used DE for pest control 4,000 years ago. The American Indians often stored grain with dust to protect it. Soil and clay dust is used by birds taking “dust baths” to free themselves of mites and other parasites. In the United States, DE and inert dusts have been used to control codling moth larvae, flea beetles, bed bugs, cockroaches, termites, ants and other insects. In fact, many pest management professionals have found that diatomaceous earth can be a useful tool in structural pest control (Ebeling 1971).
Inert dusts kill insects by desiccation. They desiccate not by absorbing water, but by removing by abrasion or absorption the outer layer of wax or grease that is part of an insect’s exoskeleton. Due to its highly porous nature, DE is one of the most effective of all natural inert dusts. It absorbs waxy fats and oils (lipids) from the epicuticle (skin) of insects and other invertebrate pests. Once the waxy, oily coating is removed, the insect cannot retain water and dies due to dehydration. Partial water loss makes them thirsty, but most insects die when about 60 percent of their water is lost. Silica gel and fumed silica are synthetic amorphous silicas (SiO2) that also kill insects in this way (Ebeling 1961; Ebeling 1971).
Like silica gel, diatomaceous earth is a form of amorphous silica. It is a natural product composed of billions of fossilized microscopic diatoms. Diatoms are aquatic one-celled creatures that produce most of the food and oxygen found on earth. They also represent the major way that silicates from the earth’s crust are recycled. They extract dissolved silica (SiO2) from rivers and oceans and incorporate it into their porous shells. When the living creature dies, shells sink to the bottom of the ocean, river, or lake and accumulate. Over millions of years, the sediments become diatomaceous earth deposits (Calvert 1930; Quarles 1992).
FRESHWATER OR MARINE DE? Diatomaceous earth can originate in fresh water or salty seas. The physical properties of DE vary with its source. Under a scanning electron microscope, freshwater DE looks like a carpet of hollow porous cylinders that are riddled with holes. It has an uncanny resemblance to some breakfast cereals. Most of the individual diatom shells survive compaction during deposition and the impact of mining, drying, milling and classifying. As a result, freshwater diatomaceous earth products contain a high percentage of intact shells with both an interior void space and interior and exterior surfaces. Freshwater diatomaceous earth is mostly amorphous, containing less than 1 percent crystalline silica (Quarles 1992).
On the other hand, marine diatoms tend to be larger, lacey and fragile. Few survive the compaction of deposition and the impact of mining, drying, milling and classifying. Consequently, natural marine DE contains a high percentage of shell fragments with almost no interior void space. In general, freshwater diatoms are more uniform in shape than marine diatom fragments. Marine DE products have a greater range of size and shape and a larger number of smaller, irregularly shaped particles. Marine DE also has larger amounts of crystalline silica (Subramanyam and Hagstrum 2000).
Either freshwater or marine DE can be calcined, heated to high temperatures. Calcined material should be avoided if it is used as a pesticide. This process makes DE a better filtration material but destroys its desiccant, insecticidal properties. It also increases the crystalline silica content to 25 percent or more; inhalation of significant amounts of crystalline silica over long periods can lead to lung cancer (Quarles and Winn 2006).
BETTER FOR STRUCTURAL PESTS? Freshwater fossils met with early commercial success in pest control and are easy to apply without clumping or caking. Many structural pest control specialists believe that freshwater diatomaceous earth is more effective than marine DE in treatment of pests such as cockroaches (Katz 1991). One hypothesis is that intact freshwater diatoms, with their interior and exterior surfaces, have a greater electrostatic attraction to insects, and are more likely to cling to the insect than are marine diatoms. In fact, laboratory experiments have shown that with the same period of exposure, larger amounts of freshwater DE adhere to insects such as crickets, and mortality rates are higher compared to marine DE (Quarles and Winn 2006).

Diatomaceous earth (DE) is a geological deposit consisting of the fossilised skeletons of numerous species of siliceous marine and fresh water unicellular organisms, particularly diatoms and other algae. Many of these fossilised sedimentary layers originated at least 20 million years ago in the lakes and seas of the Eocene and Miocene epochs. After quarrying, crushing and milling, a fine light dust is obtained, containing porous particles with certain abrasive properties and the ability to absorb lipids to about three or more times the particle mass. Any diatomaceous earth with high oil absorbing capacity is a potential insecticide. Beyond the absorbing capacity, the size of particles, uniformity and shape of the particles, pH, and the purity of formulation affect the compound's insecticidal efficacy. Insecticidal diatomaceous earth should be a highly pure amorphous silica, having particles of equal diameter (< 10 mu m), pH < 8.5, containing the least possible number of clay particles and less than 1% crystalline silica. The particles of diatomaceous earth are easily picked up by rough bodied insects. The particles damage the cuticle through hydrocarbon absorption and abrasion making the cuticle permeable to water which rapidly leaves the insect's body causing death from desiccation. In this paper the advantages and disadvantages of diatomaceous earth as an insecticide and its scope of use are discussed. Briefly, the description of DE application, the modes of action and its uses are described. Tests results show great variation in physical properties and efficacy against insects among DEs from different geographical locations. Environmental factors affecting efficacy and the potential scope of DE use are discussed.

The efficacy of dry dust and slurry applications of Silico-sec® and Diasecticide™, applied to glass and plastic surfaces, was assessed in the laboratory against the beetles Tribolium castaneum, Sitophilus granarius and Oryzaephilus surinamensis, the mites Acarus siro and Lepidoglyphus destructor, and against larvae of the moth Ephestia kuehniella. For the insects, doses of 5, 10 and 20 g/m2 were evaluated for all preparations, while for the mites 0.5, 1 and 2 g/m2 of the dry dusts, and 2.5, 5 and 10 g/m2 of the slurries were assessed. Mortality was evaluated after 7 days and 24 h for the insects and mites, respectively, in conditions of 15 °C and 80% r.h., chosen to represent typical UK conditions immediately after harvest. The Silico-sec® dry dust was the most effective treatment with mean mortalities ranging from 93–100% for all the pest species at all doses. The Diasecticide™ dry dust was ineffective against T. castaneum and S. granarius with mean mortalities ranging from 86–98% for the other species at the highest dose. With both DEs the slurry applications were generally less effective than the dry dusts at equivalent doses. Oryzaephilus surinamensis was the least tolerant insect species and S. granarius and T. castaneum the most tolerant. The mite A. siro was less tolerant than L. destructor.

Introduction
In the UK, synthetic pesticides have traditionally been used to treat the structure of empty grain stores between harvests to control residual pest populations. However, the number of pesticides currently registered for this use is decreasing following concerns over food and environmental safety, and the development of resistant pest populations. With the continued requirements for pest-free grain, the need to assess alternative compounds is of increasing importance.
One natural product that has had increasing use in pest control is diatomaceous earth (DE), which is formed from fossilised diatoms. DE dust is mainly composed of amorphous silica and has a variety of applications, including use as a filter aid, mineral filler as well as an invertebrate control agent.
In stored-product protection, DEs have proved effective as grain protectants (Desmarchelier and Dines, 1987; Subramanyam et al., 1994) and structural treatments to storage facilities (Bridgeman, 1994, Bridgeman, 2000; Wright, 1990; Desmarchelier et al., 1993; McLaughlin, 1994). The products contain no chemical insecticide or knock-down agents, have low mammalian toxicity, do not leave harmful residues, are effective against chemical-resistant species, are persistent and are stable at high and low temperatures (Subramanyam et al., 1994; McLaughlin, 1994). DEs have a physical mode of action. Dust is picked up as pests walk over a treated surface with damage to the cuticle caused by abrasion and sorption of cuticular waxes resulting in loss of water from the body leading to death through desiccation (Ebeling, 1971).

Diatomaceous earth is environmentally friendly and easy for gardeners to find, but what is it? In what situations is it helpful in the garden?
There are many products designed for all kinds of situations that work because they contain diatomaceous earth. Diatomaceous earth is naturally occurring and found in underground deposits around the world. These deposits are made of fossilized diatoms, tiny organisms that are found in water.
After being mined, diatomaceous earth is used in many ways, including for pest control.
How does diatomaceous earth work?
While diatomaceous earth comes in a couple of different forms, whether it's in a powder or a liquid when it comes to controlling insects, the principle is the same.
Diatomaceous earth works when it comes into contact with insects. It doesn’t need to be eaten. Instead, insects and other arthropods need to put their bodies in direct contact with the diatomaceous earth. The product scrapes the insect, removing oils and fats from the outside of the insect’s body. The removal of these substances can cause the insect to dry out. The scrapes themselves can also aid in this drying and dying process.
What pests can it control?
Diatomaceous earth works best on insects and other pests that are softer bodied. It is most likely effective against soft-bodied pests like slugs, but unlikely to have a major impact on a large, hard-sided potato beetle or Japanese beetle. It can also work on pests that infest homes.
What does my garden need for diatomaceous earth to control pests?
Diatomaceous earth relies on insects drying out, so the whole process works best in dry environments. You need to reapply it after rain, watering, or dew exposure.
It also works best when it isn’t compacted, so again, rain or foot traffic will render it ineffective. Some studies have found that diatomaceous earth does very little in humid environments, meaning it may not perform well during Minnesota summers at all.

The development of polymeric nanocomposites using clay minerals as a Nano filler is of great interest to researchers and industry.. this strategy improves the thermal and mechanical performance and changes the surface finishing and the processing characteristics. The Attapulgite  (ATP) has a large surface area, strong absorption capacity superior to any other natural mineral, good mechanical resistance and thermal stability. These properties make ATP an ideal candidate for reinforcing polymeric materials.

The most common means of reducing the particle size of solids is by grinding, a process which can affect the surface properties and the behavior of the solid in later stages (granulation, compaction, etc.), and which can influence the end-use properties of the final product. Inverse gas chromatography (IGC) measurements were used here to evaluate the influence of grinding, in a ball mill, on attapulgite. ....The stability of the surface energy with respect to the grinding process was seen to be related to the particular fibrous structure of the attapulgite clay.

This article focuses on integrated pest management (IPM) in historical interiors, where authenticity is an important part of the audience's experience. The brown carpet beetle Attagenus smirnovi Zhantiev (Coleoptera: Dermestidae) and the Berlin beetle Trogoderma angustum Solier (Coleoptera: Dermestidae) have been permanently present for two decades in the National Museum of Denmark’s exhibition The Victorian Home, located in central Copenhagen. Pest control is increasingly challenged in the old flat, originally furnished in 1890. The most recent measures, i.e. treating the premises with diatomaceous earth (DE), provided encouraging results. Using blunder traps, a reduction of A. smirnovi and T. angustum was demonstrated. In rooms where the application of DE was difficult due to heavy, hardly movable furniture, the effect of DE was reduced. A promising plan for future pest control was described for the premises. In addition, a short introduction to The Victorian Home is given.

Attapulgite (ATP) is a natural hydrophilic clay mineral known for its reactive -OH groups on the surface and having a layer chain like structure with exchangeable cations in its framework channel. It was reported by Zhu et al. [18] that modified hydrophobic ATP through cation exchange showed high absorption capacity and selectivity to organic solvents and oils owing to its mesoporous structure and hydrophobic treatment which allow it to be effectively applied for crude oil biodegradation issues. ...

Wheat grain containers or silos can be perfect habitats for insects, which generate large economic losses to grain production. Natural alternatives to synthetic insecticides have grown in popularity because of health, economic and ecological issues. Diatomaceous earth is a natural compound that has an insecticide effect by enhancing an insect's dehydration with no toxicity on mammals including humans. The aim of this study is to confirm the effect of diatomaceous earth as an insecticide for the wheat grain pest, the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae) and demonstrate its underlying mechanisms as an insecticide by open-flow respirometry and scanning electron microscopy.
RESULTS
Survival bioassays of T. castaneum revealed a dose-dependent insecticide effect of diatomaceous earth. Gravimetric measurements showed that 2 days exposure to diatomaceous earth produces a significant increase of mass loss. Open-flow respirometry measurements showed an increase of total water emission rate on insects due to an increase of both, respiratory and cuticular water loss. Our study revealed that diatomaceous earth produces an increase of insect's cuticle permeability, which is responsible for elevated cuticular water loss. Scanning electron microscopy images provided visual evidence of the lipid absorbent properties of diatomaceous earth particles, and showed a tendency for higher, although not significant, damaged area of the cuticle's surface from diatomaceous earth treated insects compared to control ones.
CONCLUSION
With state-of-the art techniques like open-flow respirometry and scanning electron microscopy, we demonstrated the underlying mechanism of diatomaceous earth as an insecticide and provided new cues for understanding the properties of the cuticle and its ecological importance. © 2024 Society of Chemical Industry.

Pollution from heavy-metal ions has become a major challenge to the global fight against environmental pollution. Given the availability of various low-cost and environmentally friendly adsorbents, adsorption has become the most efficient technology for the removal of heavy metals from water. In this study, attapulgite (ATP) was directly functionalized by coupling with an aminosilane agent. Analysis showed this maneuver provided a suitable adsorbent for the removal of lead ion (Pb2+) from an aqueous solution. The effects of several parameters including solution pH, contacting time, adsorbent dosage, and initial Pb2+ ion concentration were investigated. Batch sorption results showed that the adsorption process was rapid and over 98% of Pb2+ was removed within 30 min at the optimal pH 4.0. The maximum adsorption capacity at 25°C, calculated by the Langmuir isotherm, was 82.17, 78.80, 61.13, and 28.56 mg/g for γ-divinyltriaminepropyl-methyldimethoxylsilane-grafted attapulgite (KH-103-ATP), γ-aminopropyl-methyldiethoxysilane-grafted attapulgite (KH-912-ATP), N-(β-aminoethyl-γ-aminopropyl)-methyl-dimethoxysilane-grafted attapulgite (KH-602-ATP), and ATP, respectively. Moreover, molecular dynamics simulations of adsorption behaviors of heavy-metal ions at attapulgite surfaces (010) modified by aminosilane agents were carried out. Both the PMF value and diffusion coefficient of metal ions suggest that KH-103-ATP owns the highest rate constant and capacity compared with the other two. And the analysis of free energy and results of XPS characterization revealed that Pb2+ formed covalent bonds with the nitrogen atom of aminosilane agents.

Major issues associated with the currently used chemical-based insecticides are insect resistance and toxic residues causing health and environmental risks, with the need for the development of more advanced and environmentally friendly solutions for pest control. In particular, the grain industry needs to reduce its reliance on synthetic pesticides used for stored grain protection because of insecticide deregulation, resistant populations and consumer concern over insecticide residues in food and the environment. One of the promising solutions to address this problem is the use of diatomaceous earth (DE), particles from naturally occurring silica minerals formed by fossilization of green algae (diatoms), which has been successfully proved for many years to have very strong insecticidal effects and could provide chemical-free, resistance-free and environmentally friendly pest control. The unique insecticidal properties of DE particles are based on physical adsorption and abrasion of epicuticular lipids and fatty acids, leading to desiccation of insects and their death. In this chapter, we present recent developments in this field, describing the basic structural and physicochemical properties of DE silica particles, and the influence of their origin, particle size, chemical composition and dosage, as well as the physical conditions (temperature and humidity) and insect species, on their insecticidal performance, including their limitations. Finally, we present the current stage of development of new enhanced DE formulations and their future prospects.

Diatomaceous earth is often touted as a do-it-yourself remedy for bed bugs. In this study, University of Kentucky researchers and pest professionals put it to the test under real-world conditions.
 
Diatomaceous earth and other abrasive dusts have been used as insecticides for millennia. Our ancestors coated themselves with earthen dusts to rid themselves of external parasites. Early civilizations also used them to protect grain from pests during storage. Of all insecticide powders, diatomaceous earth (DE) has probably received the most public attention. Do-it-yourself pest control outlets have been marketing diatomaceous earth as a non-toxic, “eco-friendly” alternative for years. The material’s purported effectiveness against bed bugs, however, is what really put it in the spotlight. Frequently cited as an effective, reduced-risk tool for managing bed bugs, the compound has become a favorite of bed bug blogs and advocacy groups.
 
Understanding DE.
Diatomaceous earth is an off-white, powdery mineral mined from beneath long extinct bodies of water. The deposits consist of fossilized diatoms, microscopic single-cell algae whose hardened walls contain silica. Viewed under a powerful microscope, the fossilized remains look like hollow, perforated tubes. Diatomaceous earth has many industrial applications. Due to its porosity and hardness, the compound is used as a filtering agent by various industries. Because of its abrasive qualities, the mineral is also incorporated into cleansers, polishes and pesticides.

Slow-release fertilizers could improve the productivity of field crops and reduce environmental pollution. So far, no slow-release fertilizers are suited for maize cultivation in semiarid areas of China. Therefore, we tested attapulgite-coated fertilizers. Attapulgite-coated fertilizers were prepared by dividing chemical fertilizers into three parts according to the nutrient demand of maize in its three main growth stages and coating each part with a layer of attapulgite. This design is novel and unique, satisfying the demands of maize throughout the whole growing season with slow release of nutrients from the coated layers. A field experiment was conducted in 2010 and 2011, using three fertilizer rates, in kg/ha: 94.22 nitrogen (N) and 22.49 phosphorus (P), 139.09 N and 38.98 P, and 254.23 N and 50.98 P. Five types of fertilizers were compared: 20 and 30 % attapulgite-coated chemical fertilizer, 20 and 30 % attapulgite-mixed chemical fertilizer, and chemical fertilizer only. The results show that the soil mineral N and available P of attapulgite-coated fertilizer has a slow-release behavior that allows a better synchronization between nutrient availability and plant needs. Attapulgite-coated fertilizer increased the grain yield by 15.1–18.4 %. The use of attapulgite-coated fertilizers also improved partial factor productivity of N fertilizer by 10.0–26.7 % and P fertilizer by 11.0–26.7 %, compared with the control fertilized without coated formulates. Given their good performance, the attapulgite-coated fertilizers could be a promising alternative slow-release fertilizer for sustainable agriculture in semiarid areas.

To improve fertilizer use efficiency and minimize its negative impact on environment, a slow-release nitrogen and boron fertilizer with water-retention was prepared. Wheat straw was used as skeletal material in copolymerization on which acrylic acid monomer can be grafted to form superabsorbent composite. Urea and borax were introduced to provide nitrogen (N) and boron (B) nutrients, respectively. The product possessed a core/shell structure. Its core was urea in attapulgite and alginate matrix, and the shell was chemically modified wheat straw-g-poly(acrylic acid)/attapulgite (CMWS-g-PAA/APT) superabsorbent composite containing urea and borax. The effects of the amount of cross-linker, initiator, chemically modified wheat straw and attapulgite on water absorbency were investigated and optimized. The water absorbency of superabsorbent synthesized under optimal conditions was 186 g g−1 in tap water. Ammonia-selective electrode and inductively coupled plasma results showed that the contents of the nitrogen and boron of the product were 23.3% and 0.65%, respectively. The water retention capacity and the slow-release behavior of N and B of the product were investigated. The results showed that the product with slow-release and water-retention capacity, being economical, nontoxic in soil and environment-friendly, could be found good application in agriculture and horticultural.

Inert dusts are promising alternatives to conventional insecticides against numerous stored-product insect species. Diatomaceous earth formulations are based on natural substances and are registered for direct application on grain in many parts of the world. The objective of this study was to evaluate the effectiveness of three diatomaceous earth formulations (namely Silicid, Celatom® MN-23, and SilicoSec®) against adults of a wide range of stored-product beetle species. Specifically, seven stored-grain beetle species were tested, including three primary colonizers and four secondary colonizers, which are commonly found in stored cereals and other relevant commodities in Greece. The experimental units for the bioassays were plastic cylindrical vials. Twenty grams of soft wheat was filled in each vial and twenty adults of each species were placed in each vial, with a separate series of vials for each species. Mortality levels were recorded after 3, 7, 14, and 21 days of exposure. After that, the vials were kept for additional 65 days to assess progeny production. Our results indicate that among the tested diatomaceous earth formulations, the application of Silicid resulted in complete control of the major stored-product insect species. Offspring production was noted only for primary colonizers.
Abstract
Diatomaceous earth (DE) formulations are promising alternatives over the use of traditional insecticides. In the present study, a series of laboratory bioassays was carried out to assess the efficacy of three diatomaceous earth formulations, i.e., Silicid, Celatom® MN-23, and SilicoSec®, for the control of a wide range of stored-product insect species in soft wheat. The species tested were Tribolium confusum, Tribolium castaneum, Sitophilus oryzae, Sitophilus granarius, Rhyzopertha dominica, Oryzaephilus surinamensis, and Alphitobious diaperinus. Different dose rates, i.e., 0 (control), 100, 300, 500, and 1000 ppm, were used for each of the aforementioned dust formulations. Mortality levels of the exposed individuals were assessed after 3, 7, 14, and 21 days of exposure. Moreover, progeny were counted 65 days later. Based on our results, dust formulations were effective for the control of most of the stored-product beetle species tested. Among the DE formulations tested, Silicid could adequately control the stored-product insect species. Complete suppression of offspring was observed only for secondary species (T. confusum, T. castaneum, O. surinamensis, and A. diaperinus). For primary species (S. oryzae, S. granarius, and R. dominica), the lowest number of progeny was observed in wheat treated with Silicid. For instance, in the case of R. dominica, significantly fewer individuals were produced in Silicid-treated wheat at the highest dose rate. The results of the present study aim to encourage the utilization of DE in stored-product protection as an integrated pest management tool. Additional experimentation is required to apply the tested DE formulations in the field and on different surfaces.