© M.F. Potter.

Desiccant dust has been around in one form or another for decades. For some pest management professionals, it’s a go-to product for controlling and preventing bed bugs. Others can benefit greatly from its use.

WHY? Desiccant dust kills bed bugs by damaging the waxy layer of the cuticle that helps them retain moisture, thus causing them to dry out.

So far the pests haven’t figured out a way to resist dehydration even though some have developed ways to resist conventional insecticides. “Resistance to desiccating dust is exceedingly rare in the insect world,” said Mike Potter, urban entomologist, University Kentucky.

Neither do the dusts lose efficacy like some liquid insecticides once they have dried on treated surfaces.

“These desiccant dusts are one of the few products that are available right now that work after the technician has left the building,” said Dini Miller, urban entomologist, Virginia Tech, of dusts’ long-lasting residual activity.

Lab tests by University of Kentucky researchers found that silica gel dust applied to carpet substrates remained potent for 18 months and that even a short exposure to the dust was lethal for bed bugs, achieving 100 percent mortality within two days. When the researchers applied the dust to bed-bug-infested apartments that had neither been prepped nor treated by other means, they achieved a 98 percent reduction of the pests.

NOT WITHOUT LIMITATIONS. Using desiccant dust poses some challenges, however. Most notably, it is lightweight and a heavy-handed application can disperse it readily into the air. Silica gel in particular is very “floaty,” said Potter.

“If you use a hand duster, you’re going to have a mess and you’re going to have this product all over the room and all over personal items,” said Lawrence Washburn, president of Blue Diamond Exterminating in Hyden, Ky. The dust is particularly noticeable when over-applied on dark surfaces.

PMPs who work in low-income housing also may have an unconscious bias against desiccant dusts as it’s not uncommon for residents to buy dusts like diatomaceous earth and apply it improperly, usually much too heavily. As such, the insects avoid the dust or walk across it when it becomes damp and ineffective.

Here DE is brushed along seams, folds and edges (as opposed to “puffed”) to avoid drift.
© M.F. Potter.

“I think this has hindered their use in the pest control industry because these guys see residents misapplying it and not getting very good results,” said Miller.

The advantages of using a desiccant dust, though, far outweigh the challenges. “Most companies should be really looking at this and the best way to apply it,” advised Miller.

Pros-in-the-know shared how to make the most of these products:

The application of diatomaceous earth (DE) needs to be thorough, targeting where bed bugs are found or likely to occur.
© M.F. Potter.

Less is definitely more. An application of desiccant dust must be so light that the bed bugs are willing to walk through it, which is what causes them to pick up a lethal dose. “If you apply it too heavily, I think a lot of insects are smart enough to avoid it,” said Miller.

“If you see the dust you have too much applied. You should barely be able to tell it’s even there,” added Elia Levin, owner of 5 Star Pest Solutions, Indianapolis.

Focus on points of interception. Apply desiccant dust where bed bugs most likely will come in contact with it. Depending on the level of infestation, this may involve dusting the legs of bed frames and furniture, the seams, tufts and framework of upholstered furniture, the seams of mattresses and the underside of the box spring before encasing them.

“Your bed bug has to come in contact with the product. Obviously, it has to be put where they behaviorally are going to be either living in a brood center or meandering about” in search of a blood meal, said Levin.

Choose the right duster. Hand dusters don’t cut it. “I’ll see the technicians out there who are just puffing it and I don’t know that that’s really light enough,” said Miller of the resulting distribution of dust.

A power duster will provide the appropriate distribution, but “different dusts work better in different dusters,” she cautioned. “It’s not one size fits all” and it’s best to figure this out before investing in (or ruining) expensive equipment, she said. PMPs also may want to use equipment designed for specific applications, such as for dusting along carpet edges.

Use a brush. “You need to be precise with it; you need to be able to put it exactly where you need it,” said Washburn of the dust. As such, he uses a small brush (e.g., a cosmetic or soft paint brush) to lay the dust on mattress seams, bed legs and the undersides of upholstered furniture and box springs.

“If you use a bellows duster and just puff against the surface it’s just going to bounce back at you,” said Potter of the dusts’ tendency to go airborne.

Eliminate inter-unit travel. In multi-unit housing where bed bugs can move between units, use a power duster to apply the dust above shared drop ceilings (often found in bathrooms) and in the voids behind medicine cabinets and utility openings.

Also apply dust around the unit’s perimeter where the carpet and baseboard meet. “Desiccant dusts are excellent barriers to put around there,” said Miller.

Avoid unnecessary work. Don’t waste time pulling up carpet edges or dusting every crack and crevice, wall void or utility opening if an inspection shows the pests aren’t likely in those places. Large infestations of bed bugs are found everywhere in a residence, but in the early stages of an infestation they’re more predictably found near the sleeping person, said Potter.

Different levels of infestation and clutter require different strategies for controlling the pests, advised Miller.

Think outside the box (spring). Miller works in public housing where “there are no box springs.” And different cultures prefer to sleep on different types of beds, from those of stone to roll-up mats. “We need to think how these desiccant dusts can be applied in a non-hazardous way in situations where the people don’t have the traditional bed,” she said.

Always read the label. “The number one mistake with desiccant dust is not being really familiar with the label and where you can apply it and where you can’t,” said Miller. Labels for products without added insecticide are generally broad; still, experts advised not to apply the dusts where residents might come in contact with them.

And while airborne silica gel or DE is not considered a health hazard, Potter urged PMPs to take extra care to limit this around people with respiratory ailments. He also said silica gel was far more effective as a dust than as a suspension mixed with water, as allowed for on the label.

Play defense. Most PMPs combine the use of desiccant dust with other bed bug treatments, such as conventional insecticides or heat. Brad Carrier, owner of Bugsy’s Pest Solutions, Waterloo, Iowa, uses silica gel as “a defense mechanism,” a hedge against the day he runs into insecticide resistance.

Washburn uses the dust alone to prevent bed bug introductions from becoming bigger problems. Two years ago he treated the perimeter carpet edges of the rooms at a resort and hasn’t had a bed bug problem call since.

A desiccant dust “can be used either as a primary or a supporting secondary material. It depends on the level of infestation and how quickly you need to accomplish the elimination,” said Levin.

Offer as an alternative. Washburn often gets calls from people with bed bug problems who cannot afford professional pest control. “That’s one of the big problems with really getting a handle on what’s going on with bed bugs,” he said. As such, he advises callers on how to purchase silica gel and apply it with a brush. Potter would like to see an affordable application device developed for the consumer market to help people more effectively do this.

Satisfy the desire for green. “Desiccating an insect totally makes sense. How green do you have to be to use something that s

imply dries it out,” asked Levin. As such, Bryan Nichols, owner, Advanced Maintenance and Pest Solutions, Chicago, uses silica gel as a stand-alone green treatment for some jobs. “It’s been very successful in getting rid of the bed bugs and also keeping my clients more at ease. It has the safety profile that allows us to really breeze through a lot of the chemo-phobic questions that come about” and also reduces the risk should a resident return home to find that a treatment was done but who wasn’t told of this beforehand by the landlord, said Nichols.

“It’s a great tool to have in your toolbox,” said Levin.

The author is a frequent contributor to PCT.