[Focus on Foam] Foaming Fundamentals

Features - Pesticide Issues

Foam can be a valuable tool because of its ability to move laterally and vertically throughout an enclosed void.

September 28, 2012

Editor’s note: The following article is an excerpt from the “Equipment” chapter in the recently published Mallis Handbook of Pest Control, 10th edition, www.mallishandbook.com. The chapter was authored by Judy Black, technical director for The Steritech Group. She can be reached at jblack@giemedia.com.

Adding a surfactant and injecting air into a liquid pesticide solution will change the formulation into a foam. The use of foams has become popular in termite control as well as for sanitation purposes to help reduce filth flies and for penetrating wall voids for other pests. Foams have the ability to move laterally and vertically throughout an enclosed void. By physically filling the void with insecticide foam, the professional ensures that the insecticide contacts all surfaces in the void. This type of treatment may have distinct advantages over sub-slab and void injection of (non-foam) liquids where coverage laterally and vertically is dependent on pest management professionals’ use of specialized tools and drilling many access holes.

Foaming equipment can be hand-held, portable electric units or attachable to existing spray systems. Professionals can choose from a variety of injection tools to fit their service needs. Tools resemble termite slab injectors and void injectors. Shut off can occur at the nozzle tip or at the valve. Tools with tip shut-off give more precise control at the injection site but will cause more “shearing” or breaking of the foam bubbles from moving around metal mechanisms in the tip. Shearing will result in a “wetter” foam (more liquid, less air). Adjustable needle valves on tools can help compensate for this occurrence.

Handheld foamers operate with compressed air from a hand pump. The insecticide and surfactants are mixed in a small plastic tank (usually one-quart capacity), and the foam is generated as the mix moves through a specialized tip. The foams are generally wet with some variability based on the pressure applied through the sprayer. These foamers are used for very small spot treatments, and more frequently, to apply degreasing/sanitizing materials. These foamers are useful, but not practical in situations where large amounts of foam are required.

Nowhere for Wasps to Hide

Syngenta’s Optigard Flex was introduced as a zone treatment with foam for ant control. But it soon was discovered that the foam component worked wonders for another type of pest.

“We started adding insects to the label later,” said ElRay Roper, senior technical representative, Syngenta. “It works well against Hymenoptera. Yellow jackets will nest in the ground and wall voids.”

For a variety of hard-to-reach places, a foam application of Optigard Flex proved an effective method to control these pests. Roper said mixing Optigard Flex at .1 percent with a 15 to 1 expansion ratio foam injected into an area worked wonders.

“You just inject that into the void with a six-foot extension wand,” Roper said. “Put the nozzle at the entry of the nest, inject foam for three or four seconds. I’ve never had failure. Within an hour all activity is stopped. One of the first I did was under a brick veneer in my own house.”

The versatility of a foam application is useful in situations such as this for reasons that a spray application may fail, Roper said. “You get very good expansion into these voids and a good coating in these nests. Unlike a spray, you may not get it on the area where the wasps are making contact. With a foam you actually fill up a void. It works the same way as filling up a termite gallery.”

In a field demonstration with the European wasp, Roper said Optigard Flex worked well. “Oft times when you have a home, the people who put up the siding and aluminum work got it tight and did a good job. Certain homes had poor workmanship, with wasps nesting in soffits. Optigard foam, took them out every time.”

The foam application of Optigard took out wasps nesting in a metal hand rail, in a children’s swing set, in a basketball standard — the wasps couldn’t hide. “PMPs probably have thousands of other examples where these insects nest,” Roper said. “Foam works really well in these types of applications.”


Spot foamers are used to treat small areas, such as isolated sub-slab voids and bath traps, against organic debris build up in commercial facilities and often for termite retreatments. A typical rig consists of a spray tank with a 1- to 5-gallon capacity, an electric compressor to deliver air pressure, an application hose and treatment tools. Most are mounted on wheeled carts. The Pestifoamer (Richway Industries), VersaFoamer 4000 (B&G), and B&G Wood Treatment System are examples of spot foamers (see Figure 1, right). Units able to apply both foams and liquids using a dual-line system offer versatility to switch formulations without changing equipment. These units are electrically powered and most are now pre-calibrated. Adjusting a needle valve in the application tool will change the foam density.

In-line foaming equipment is used for high-volume applications, such as whole sub-slab injection or treating large volumes of hollow voids (e.g., block construction). In-line foamers may be “piggybacked” on existing rigs where a selectable control valve or injector determines foam or liquid treatments. Another type of in-line foamer requires tank mixing of the foaming agent. Choosing between foam and liquid applications is done on a metering system on a separate cart. Some carts are portable and can be brought into basements. A third system uses multiple hose lines to allow for liquid treatments or foam to be produced at the treatment tool.

Canned foaming products have fairly recently appeared on the market. These products have multiple target pests and are designed for void applications.


The author is technical director for The Steritech Group and a PCT contributing writer. She can be reached at jblack@giemedia.com.

Mallis Handbook of Pest Control

The tenth edition of the Mallis Handbook of Pest Control — an industry standard in education for more than 65 years, is the leading reference source in the structural pest control industry. It is a scientific guide and practical aid for the biology, behavior and control of structural pests. The 24-chapter publication provides pest control operators with the information needed to deliver effective, environmentally conscious pest management services in today’s competitive business climate.

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For more information or to order visit www.mallishandbook.com or call the PCT Bookstore at 800/456-0707.