7. Desiccant Dusts for the Control of Bed Bugs

Always check with the certifying agency before using a new product or material. This guide is not a substitute for pesticide labeling. Always read the product label before applying any pesticide.

Insects and other arthropods (ticks, mites, spiders, etc.) have an exoskeleton, the hard, outer surface that provides the shape of the insect. A waxy layer, called the cuticle, serves as a barrier to prevent water loss. Without the cuticle, insects and other arthropods rapidly lose water from their bodies and die.

Desiccant dusts have long been used in pest management. They work by either scratching or abrading the exoskeleton or by absorbing the waxy cuticle layer. The outcome is the same in both cases – the insect loses its ability to retain water and dies from desiccation or water loss.

Diatomaceous earth and silica gel are two types of desiccant dusts used against bed bugs. These products are non-toxic dusts and do not contain active ingredients such as pyrethroids or neonicotinoids, two common pesticides.

Diatomaceous earth is the fossilized remains of algae (called diatoms). It is a naturally occurring mineral, like talcum powder. When an insect crawls over diatomaceous earth, it scratches the insect cuticle and makes the insect vulnerable to desiccation. Silica gel, on the other hand, is a synthetic, fluffy white powder that is made from silica (the name is misleading – it is a powder and not a gel). Silica gel sticks to and adsorbs the waxy cuticle of the exoskeleton. The outcome is the same: the insect dies slowly from desiccation.

How to Use Desiccant Dusts:

• Read all label instructions prior to using a desiccant dust. Label instructions might include recommendations for personal protective equipment (gloves, mask, eye protection), and will provide details about suitable application methods.
• Dust applications should be thin coats of the material that create a light film and/or are barely perceptible.
• DO NOT OVERAPPLY! When treating furniture, the bed frame, carpet edges, etc., a soft-bristled paintbrush or a cosmetic brush (Fig. 73) may be used to apply a very thin coat to cracks and crevices (Fig. 74).
• Remember that these materials work by affecting the insect exoskeleton – essentially requiring that the insect crawl through it. Applying desiccant dusts to open areas will not force bed bugs into complete contact with the material and may not affect their survival. Instead, apply dusts to cracks and crevices where bugs will press against two or more surfaces, exposing themselves to the material.
• Common areas of dust application include cracks and crevices of floor molding, bed frames, couches/sofas, electrical outlets, or other areas where insects or their evidence is visible. Some products can be used directly on box springs and mattresses – with applications focused on areas of bed bug activity such as the seams/folds of the mattress and the underside of the box spring [read the label for specific instruction].

Consider This:

• There is some evidence that silica gels perform better than diatomaceous earth. This is partially because of the way the products work: silica gels adhere to the exoskeleton and adsorb the cuticle layer, whereas diatomaceous earth scratches the cuticle. It is important to note that juvenile stages of bed bugs may be able to overcome both products when harborages are sufficiently humid, if they are recently fed (blood is high in moisture), or if they molt soon after exposure to the dusts.
• Desiccant dusts will clump in high humidity or excessive moisture. Clumped dusts will not adhere to the insect’s exoskeleton to cause desiccation. High humidity may also reduce the effect of dusts because desiccation is less likely.
• Apply desiccant dusts in a thin layer, as indicated on the label (Fig. 74). Large amounts of desiccant dusts may be repellant to bed bugs, and are likely to be less effective.
• Compared to synthetic insecticides, desiccant dusts are a safer alternative when used according to the label.

Advantages and Disadvantages of Desiccant Dusts:

• Advantages:
• Silica gels can also be mixed with water and used as a spray formulation. Instructions on the label should be followed to avoid clogging applicator tips on spray equipment.
• When applied in dry areas and according to label instructions, desiccant dusts will have a much longer residual activity than most liquid insecticides. The physical properties of the dusts do not change over time and will abrade or absorb the exoskeleton, whereas chemical insecticides can decay over time in response to light, moisture, and bacteria.
• Dusts picked up by one insect can be transferred to others in a harborage. This horizontal transfer can increase the impact of desiccants.
• Research has highlighted cost savings for multi-unit buildings when connecting walls are proactively treated with desiccant dusts.
• In some situations, desiccant dusts can be applied with minimal home preparation.
• Based on their demonstrated safety, desiccant dusts have a broad application label and can be used in a variety of sites and locations.
• Disadvantages:
• Depending on the surface of application, residue left by desiccant dusts can leave a white powdery residue. However, this powder can easily be cleaned with a wet paper towel, duster, or vacuum. Label instructions should be consulted for cleaning up excess product.
• According to the label, desiccant dusts should be applied in a manner that leaves behind a thin coating of product. This can be achieved in a variety of ways, but in many cases, special equipment is utilized, such as automated dusters.