During August we were fortunate to have Dr Bill Robinson visiting our shores and sharing his vast experience around pests in general and more specifically about application techniques, equipment and product performance. As the Technical Director of B&G Equipment for the past 15 years, he is very qualified in this area. 

Bill has a B.A., M.A. and Ph.D. with majors in biology and entomology and minors in geology, meteorology and botany. He was a Professor and Director of the Urban Pest Control Research Centre at Virginia Polytechnic Institute and State University for about 30 years. For 16 years he was a Visiting Professor and Director of the Urban Entomology Centre at Zhejiang Agricultural University in Hangzhou, China. 

Along with 20 graduate and post-doctoral students he has conducted and published research on cockroaches, carpenter ants, dust mites, fleas, flies (phorids), termites, wood-infesting beetles, insecticide resistance, wood protection, and insecticide application technology, and turf pests. He has written several books on urban entomology and a series of training manuals for service technicians. In his latest manual “The Service Technician’s APPLICATION AND EQUIPMENT MANUAL, A Practical Guide for Pest Control Professionals” he shares practical information to help you build your understanding of the intricacies of application.

Below are some key points that I took away from the workshops he ran in Australia and New Zealand.

The efficacy of an insecticide treatment depends on the combination of the insecticide’s active ingredient, formulation and application. These are the main factors that influence how long the application remains effective against the target pest. It is also important to understand the habits of the pest, such as movement and foraging. The objective is to treat substrates that will be contacted by the pest when it is in or leaves a harborage. When all these parts are in the proper sequence, control is achieved.

Modern insecticides have dramatically changed professional pest control: they are effective, selective and used at very low concentrations. The challenge for the industry is to match these insecticides with the most efficient application methods and tools. The efficacy of liquid, dust or baits depends on precision delivery to the target pest or substrate.

BASICS OF INSECTICIDE APPLICATION

The most common formulations are microencapsulated (ME, MC), wettable powder (WP), suspension concentrate (SC) and dust (D). These are designed specifically for the active ingredient and how it will be used; some active ingredients are available in more than one formulation. For example, an SC may be suitable for soil applications, but a ME is better for surface treatments. 

The formulation can influence the long-term activity of an insecticide by how it forms a residue and how the target pest is exposed to it. Foam and aerosol sprays are formats for delivering liquid insecticide. Foam can improve the spread of liquid on the surface of soil or in a wall void. An aerosol spreads a liquid in the form of droplets in a substrate, which is an air space, to improve contact with flying insects.

SUBSTRATE AND RESIDUE

Spraying a surface may seem to be a simple process, but there is a lot to consider if the treatment is to be effective and cost efficient. The objective is to apply droplets of insecticide to establish a surface residue which will be contacted by the target pest. While the equipment and the spray droplets remain the same, the composition and surface of the substrate can be significantly different.

TIME

The time between an insecticide application and contact by the target pest is important in achieving control. The residual toxicity of insecticide on exposed surfaces is limited by environmental conditions or other events that remove the residue, and by the insecticide itself. Some formulations (like the microencapsulation of DEMAND Insecticide or the suspension concentrate of ALTRISET Termiticide) stay effective longer than others.

Time is a factor for indoor applications. For flea control, spraying indoor carpeting is a typical method of control. However, it can take a few days for the liquid insecticide to move down the fibers to the base of the carpet where it will be contacted by larvae. During this time the insecticide may be exposed to damaging ultraviolet light passing through windows, or it may be damaged or disturbed by foot traffic or vacuuming. The initial residue may be less effective by the time adult fleas emerge at the base of the carpet and crawl to the surface.

The residues of wood-protection insecticides are expected to remain effective for long periods. Liquid and foam applications to structural wood produce a residue at, and immediately below, the surface. The surface residue will degrade within weeks of application, especially when the treated wood is in an attic or a crawlspace. Below the surface, where the liquid moved during and after treatment, there is a stable residue which is protected from environmental conditions and may last for years.

LIQUID APPLICATION

The primary objective of liquid insecticide application to surfaces is to kill insects that crawl on those surfaces. The droplets from the spray pattern create a dry residue on treated surfaces, then insects and other pests pick up a lethal dose when they walk on the residue. Creating an effective residue depends on using a fan-spray nozzle at optimum pressure and overlapping the spray pattern to achieve complete coverage.

Application with a crack-and-crevice straw creates a residue in narrow spaces with a stream of liquid. This application increases control and reduces insecticide exposure to people and pets. The residues remain effective for long periods because they are protected from environmental conditions

The effectiveness of liquid insecticide is not based on the amount applied, but on where and how it is applied.

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