Stinging Insect Surge

Features - Painful Pests

In an excerpt from their forthcoming field guide on stinging insects, entomologists Stoy Hedges and Gerry Wegner talk about when populations peak, becoming a growing threat to your customers. Learn how to control these pests from two of the country’s leading experts.

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Arthropods that sting or bite humans and pets comprise a wide variety of different groups of insects and arachnids. Depending on the type of pest, the treatment needed may be limited to just one technique and product (i.e., yellowjacket nest) to multiple techniques and products (i.e., bed bugs).

This article will briefly discuss the different treatment techniques and corrective strategies that may be employed to address a variety of stinging insect situations, ranging from simple to complex.

NONCHEMICAL TECHNIQUES. In some situations, control of a pest infestation may require using a nonchemical approach. These include a variety of measures from exclusion and vacuuming to physical removal and lighting. A brief review of each of these nonchemical control techniques follows.

Exclusion. The best way to prevent pests from entering a structure from the outside is through exclusion by closing off potential entry points. Larger gaps and holes can easily be sealed off from arthropod entry using Xcluder brand rodent fabric which comes in 1-inch- and 4-inch-wide rolls. Xcluder fabric can be cut to fit using scissors then pushed into gaps and openings using a putty knife, screwdriver or other flat-ended tool (Figure 1). Other types of “stuffing” material to fill gaps are available commercially. Smaller cracks can be sealed using a long-lasting silicone or polyurethane sealant designed for exterior use.

Weep holes in brick veneer buildings can be closed off by stuffing them with a piece of Xcluder fabric or insect screening. Moisture-permeable products designed specifically for insertion into weep holes are commercially available.

All foundation, gable and soffit vents should be equipped with insect screening to exclude arthropod and vertebrate pests from entering these spaces.

Where accessible in attics, insect screen also should be attached to cover the openings in roof decking associated with turbine and mushroom fans (Figure 2).

An important, yet overlooked, pest entry point in homes is found at the perimeter of soffits. When constructed, the roof decking boards do not quite reach the fascia and a gap 2 to 3 inches wide exists just under the edge of the shingles (Figure 3).

Figure 1: The best prevention strategy is by excluding pests from entering by closing off or sealing potential entry points. (Photo: Paul Curtis)
Figure 2: Insect screening installed over openings for vents in attics helps prevent pests from entering.
Figure 3: A gap exists around the perimeter of the roof line just under the shingles dripline where pests can enter (top). Installing gutter apron flashing will close off this gap (bottom).
Figure 4: Xcluder fabric can be used to close off gaps at the corners and edges of gutter apron.
Figure 5: Roof returns often have large gaps (top) that need to be sealed off to exclude wasps and bees (bottom). Note the Xcluder fabric sealing the crack to the left of the metal flashing.
Figure 6: Barrel tile roofs have many gaps large enough to admit bees, wasps or scorpions. Installing exclusion materials to close off these gaps is helpful for prevention of these pests in attics.
Figure 7: Monitoring traps are used to determine the presence of biting pests and to capture scorpions wandering inside buildings.
Figure 8: Nests of yellowjackets or bumble bees can be excavated from the ground, when necessary.

This entry point is commonly used by paper wasps, mud daubers and, on rare occasion, yellowjackets or honey bees. Installing “gutter apron” metal flashing around the roof perimeter will close off this gap from pest entry (Figure 3). It is important, though, to also seal off the edges of this flashing using something like Xcluder fabric (Figure 4).

Another pest entry point into buildings is where one roof line meets another roof — a construction feature called a “roof return” (Figure 5). The gaps here may range from less than an inch to several inches depending on the quality of the construction.

The best way to seal off these gaps is by form-fitting metal flashing over the gap, which excludes both insects and rodents (Figure 5). Holes and cracks that may exist around the periphery of the flashing can be sealed using silicone or polyurethane sealant or Xcluder fabric (Figure 5).

Buildings with barrel tile roofs (Figure 6) can have many gaps where pests can enter and can be difficult sites to exclude pests from entering. Cracks and gaps can be closed off using Xcluder fabric, high-density sealants (i.e., Vulkem), metal flashing molded to fit over the opening, or ¼-inch hardware cloth coupled with insect screen (excludes both insects and rodents).

Monitoring Traps. Monitoring traps are generally used when figuring out which, if any, biting pests (i.e., bed bugs, mites) may be present indoors and the rooms in which they are present (Figure 7). Sticky traps are also used to trap scorpions that may wander along baseboards and in attics.

Vacuuming. Pest vacuums are widely used in bed bug control programs to physically remove as many bed bugs as possible (where they are exposed and accessible). Vacuums are also used to remove honey bees from nests within structural voids, as well as live and dead yellowjackets and bumble bees from windows, skylights, floors and situations where insecticide applications may not be prudent.

Physical Removal. When fire ants, yellowjackets or bumble bees are nesting in the soil in a site where residual treatments are not desirable (i.e., animal enclosures in zoos, child play areas), the colonies may be physically removed by digging them up and transporting the nests and insects off site for treatment and disposal.

For fire ants, smearing a thin layer of petroleum jelly on rubber boots and the shovel handle is needed to help prevent stings. For yellowjacket and bumble bee nests, a shop vacuum or a battery-powered vacuum can be used — after dusk — to remove worker bees or wasps and then followed by nest extraction (Figure 8), and placement in a plastic bag for removal and disposal off site. Fresh soil may be placed into the excavated area to refill it to grade level.

Freezing. Cryonite converts liquid carbon dioxide (CO2) into a dry ice snow that when applied directly to insects will kill them by freezing (Figure 9).

The specially designed Cryonite lance creates dry ice snow in a mixture of particle sizes that delivers a maximum freezing effect upon contact onto target insects. The snow is expelled at a temperature of around -108 degrees Fahrenheit. This technology is used by a number of pest control companies in their bed bug control programs; however, it is readily applicable to subduing colonies/nests of stinging insects within structural voids and ground cavities.

A limitation is that it works by contact only and does not leave any residual deposits. Cryonite can be used in sensitive areas where residual insecticide treatments may not be prudent or allowed, including schools, daycares, many areas of hospitals, assisted living/nursing care facilities, food processing areas, pharmaceutical areas, pet stores and zoos.

The dry ice snow is instantly lethal only when directly contacting the target pest’s exoskeleton. However, even without direct contact, the ultracold Cryonite snow is capable of subduing target insects temporarily in confined spaces/cavities by quickly lowering their body temperature and rate of metabolism, and by CO2 asphyxiation.

Nevertheless, it is important to eliminate as many treatment barriers as possible by making sure pests are not protected by layers of dirt, dust or other materials. This is generally not an issue with stinging wasps and bees, which keep their nests fairly clean. It is also beneficial that persons and pets (especially tropical fish) typically need not be vacated prior to Cryonite applications.

For maximum effectiveness, Cryonite needs to be applied using recommended procedures described in the Cryonite User Manual provided by the manufacturer. It is important when applying the dry ice snow that it be applied in a layer over target insects — a layer that evaporates within 30 seconds. This technique produces the maximum freezing of the treated pest. Cryonite USA may be contacted directly for more details and information on the use of this unique technology.

Heat. Heat treatments of infested rooms or entire buildings are used to control infestations of bed bugs within rooms, buildings and infested items. Heat treatments utilize specialized heaters, in conjunction with temperature monitoring devices (thermocouples), to raise the internal temperatures to a target level (i.e., 130 degrees Fahrenheit/54 degrees Celsius) and then hold that temperature for a specific time period.

This process is highly technical to implement and requires training, experience and often expensive, specialized equipment (Figure 10) for success and should only be completed by companies prepared and trained for heat services.

Steam. The use of superheated (dry) steam applied using portable steam- generating equipment fitted with assorted attachments for specialized situations, has proven effective against several biting and stinging pests. Such superheated steam ranges in temperature from 230-248 degrees Fahrenheit. Dry steam treatment of bed bugs in upholstered furniture is an alternative to using residual insecticides and heat. Injection of fire ant nests and yellowjacket ground cavity nests using steam is an appropriate option for sensitive situations (i.e., where the use of insecticides is not an option), particularly for smaller properties.

Lighting. Insect light traps (ILTs) are used to capture flies and other flying insects that enter buildings. Primarily designed for fly control, ILTs do attract and capture wasps and bees inside. Outside, bright white metal halide or LED lamps in exterior light fixtures can attract certain pests such as thrips, corsairs or kissing bugs (Triatoma spp.) to buildings.

Advising customers to switch to yellow “bug lite” bulbs in home fixtures or sodium vapor lamps in commercial fixtures will attract far fewer of these and other flying insects to a building.

INSECTICIDE TECHNIQUES. Application techniques are those methods that involve application of insecticides to control pests in and around buildings.

Figure 9: Cryonite technology converts liquid CO2 into dry ice snow that freezes insects on contact.
Gerry Wegner
Figure 10: The use of heat to control bed bugs requires the use of specialized heaters and other equipment.
Figure 11: Treatment of cracks and openings targets the sites used by pests as harborages and entry points.
Figure 12: The battery-powered Exacticide duster can push dust deeper into larger voids and also can be used to treat even small cracks.

Crack & Crevice Treatments. A crack and crevice treatment involves the application of a small amount of insecticide applied directly into a crack or crevice (Figure 11). The insecticide should be applied in such a way that the treatment goes into and remains inside a crack and does not stray outside the crack (Note: Some product labels require clean-up of any application outside the target crevice.)

Crack and crevice treatments can be made with many different formulation types with residual dusts and aerosols being the most widely utilized formulations. Dust products have a long residual life (up to a year or longer), distribute more completely within a crack and are easily picked up by pests entering or harboring in a treated crack.

Aerosols also provide adequate distribution within cracks but may be partially absorbed by porous surfaces (i.e., raw wood). Most water-based residual products can be applied as crack and crevice treatments. Care must be taken during the PMP’s application to use an injector tube/tip on the sprayer.

Void Treatments. A void, for pest control purposes, is an inaccessible space enclosed on all sides. Examples include wall voids, the voids under the base of cabinets and the inside of porch columns. Larger enclosed spaces such as attics, crawlspaces and false ceilings are accessible to enter and so should not be considered for void treatment as described in this section.

Voids are typically treated with a residual dust formulation which will (1) penetrate and distribute throughout the enclosed space and (2) leave a long-term residual deposit which will kill new pests that attempt to enter that space.

Voids may be treated with one of several different types of dusters such as bellows dusters, bulb dusters, pump dusters, cordless electric dusters (i.e., Exacticide) or a compressed air duster (for large, inaccessible voids). Figure 12 shows an Exacticide duster in use to treat a soffit.

Yellowjackets (underground, in buildings) and hornets (above ground) enclose their nest combs within a paper covering, or envelope, which effectively forms a void.

These nests are easily treated by injecting a residual dust into the nest (Figure 13). Due to the complex interior construction of such nests, especially those of Dolichovespula spp. aerial nesting yellowjackets like the bald-face hornet, two or three injection points are recommended for dust application, for better penetration and distribution of the dust on interior surfaces.

Spot Treatments. These are applied to exposed surfaces where pests harbor and is generally limited by the product label to a maximum of two square feet in area. Water-based formulations and many aerosol products have spot treatments as an application method available on the label.

Spot treatments are generally permissible in most areas inside and outside buildings, although the label may prohibit application to some types of surfaces such as plastics or food contact surfaces.

Gerry Wegner
Figure 13: In-ground yellowjacket nests can be treated by application of a residual dust product into the nest.
Figure 14: A general surface application involves the application of an insecticide to a larger surface area such as a flea treatment shown here.
Figure 15: Perimeter treatments have a number of use restrictions on insecticide product labels.
Figure 16: A direct contact treatment involves application of an insecticide directly onto exposed insects.
Figure 17: Granular baits designed for fire ant control are typically applied using handheld or push-type spreaders.

Application of spot treatments indoors for pest control should be directed at sites where pests spend time on exposed surfaces. Examples include surfaces around paper wasp nests or carpenter bee nest entrances, surfaces around pest entry points, flea breeding sites in carpeting where host pets lounge and the backs of headboards where bed bugs harbor.

General Surface Application. A general surface application or treatment involves applying an insecticide to a large surface area. Examples include flea control applications to open areas of carpets (Figure 14), a perimeter treatment around a foundation or treatment of landscape areas under shrubs or other vegetation.

Perimeter treatments may be used for a situation where scorpions are regularly invading a building. Perimeter treatments to the foundation have restrictions on the label as to where general (or broadcast) surface applications may be applied (Figure 15). These restrictions may include:

  • General surface applications are prohibited directly onto or over impervious horizontal surfaces (i.e., concrete sidewalk, driveway or patio) that may lead off site to gutters, ditches, storm drains or bodies of water.
  • Onto and over impervious horizontal surfaces, applications are limited to spot and crack and crevice treatments.
  • Surfaces protected from rainfall or irrigation, such as covered porches and under soffits, may be treated with general surface, spot and crack and crevice treatments.
  • Treatment around windows and doors may be limited to bands applied one to a few inches up to 18 inches, depending on the product label.

Direct Contact Treatment. Applications with an insecticide applied directly to exposed pests are known as direct contact treatments (Figure 16, page 87). Typically, direct contact treatments are performed using an aerosol but can be made using a compressed air sprayer containing a residual water-based formulation.

Treatment of exposed paper wasp nests on a soffit or under a porch covering serves as an example. Exposed pests hit with a direct contact treatment will die eventually.

Baiting. As of 2020, the primary insect baits available for stinging or biting pests are for fire ant control outdoors. Several fire ant bait products are commercially available and are typically applied directly around mounds as a broadcast bait to yards and landscape areas (Figure 17).

Meat-based toxic baits targeting yellowjacket foundress queens have reduced numbers of nearby nests established in cases where such baits are accepted and compete with naturally occurring animal protein sources favored by the foraging queens early in the nest construction season.

A mosquito bait called Final Feed — introduced in 2020 — that targets female mosquitoes looking for a sugary meal can be applied outdoors to vegetation and structural surfaces. Both male and female mosquitoes visit flowers to obtain a meal of nectar soon after emergence from pupae.

Fumigation. Fumigants are penetrating gases that kill insects by disrupting their respiratory and energy functions. Fumigation is a highly complex process involving highly trained, licensed professionals and specialized equipment. Control of bed bugs by fumigation is sometimes performed and generally only in situations with severe infestations. Although effective in the elimination of existing pests, fumigation leaves no residual protection.

The author is a board certified entomologist and owner of Stoy Pest Consulting.