[Application Economics] Controlling Over Application

Editor’s note: The following article was excerpted from The Service Technician’s Field Manual. See the article in the sidebar for information about this new book.
 

In professional pest control, emphasis is usually placed on the technology of killing pests, while the cost, or economics, of the process is often overlooked. However, designed into every application tool and insecticide is the concept of application economics. This concept considers how much insecticide is being applied, and how well the application tool works in terms of amount and cost. Application technology covers the control effectiveness of treatment, while application economics covers the cost effectiveness of it — both are important.

The “more is better” approach to pest control must be replaced with the “less is more” approach. By the time a professional service provider is called, pest problems have usually become severe, and customer attempts failed. While professionals have the advantages of training, equipment and application, the customer often expects “stronger” insecticides and more treatment. The fact that precise or minimum application will achieve control is often difficult to understand for both technician and customer. However, applying more does not provide better control; more is not better, it is certainly wasteful and usually expensive. Too often, insecticides are mixed by the gallon and wasted by the ounce.

This article focuses on ways to control application economics through reducing over application.
 

Over Application. Over application occurs when more insecticide is applied than is necessary to achieve pest prevention or control. It can be a service technician spraying to run-off as liquid insecticide drips from a surface, dusting to produce a thick visible layer on the surface, re-tracing a spray pattern and over-applying to carpeting, or unnecessarily treating a section of baseboard or wall void. It may be only a few additional ounces of liquid or dust during a service call, but when it is routine with every service it becomes an expensive habit.

Over application of insecticides is a common and unrecognized practice in professional pest control. It is difficult to see because it is only a small amount, perhaps just ounces at a time. Modern application tools are lightweight, ergonomically designed and easy to use. However, a comfortable grip and a responsive valve trigger can be a problem as much as a benefit. Sometimes ease of squeezing a comfortable trigger can result in over application and extra cost.

Spraying liquid insecticide into or adjacent to pest harborages is a standard pest control practice. The application equipment combines pressurized tanks, valves and nozzles to deliver a measured amount. However, there can be considerable variability in application, due to the habits of the technician and the type and condition of the equipment.
 

Example: A technician services 15 accounts a day, and at each account applies insecticide for an extra 30 seconds with a coarse fan spray. In a single day, a gallon of insecticide is over applied, which is 20 gallons a month.
 

Surface Application. The objective of surface spraying is to establish a residue. Treating surfaces to the point of run-off is unnecessary; it wastes insecticide and increases costs. Control is achieved when a lethal amount is picked up on the feet of crawling insects, or a lethal concentration penetrates a porous surface, such as wood, to intercept larvae of wood-infesting beetles. A spray that produces a pattern of droplets on the surface can be effective and efficient. A crawling insect walking across the surface picks up a lethal dose of insecticide in a short distance of travel or short time on the treated surface.
 

Example: After a surface is sprayed to the point of being “wet,” German cockroaches walking on the dry residue are knocked down in 5.4 minutes. When the amount of insecticide applied is 200 times less than wet, the cockroaches are knocked down in 8.8 minutes. By applying 200 times less insecticide, the time to knockdown and kill increases by only 3 minutes, while the amount of insecticide used and cost is considerably less.

The coarse and fine fan sprays on standard nozzles are designed to deliver droplets to the treated surface. The pattern of dry droplet residue is sufficient for the transfer of a toxic dose of insecticide to the feet of any insect that walks on it. Within a short walking distance, a lethal dose is acquired. Spraying more does not increase efficacy, but does increase costs.
 

Crack-and-crevice Application. This is the most effective and efficient method for treating pest harborages. It treats only the surfaces regularly contacted by the pest, increases residual activity of the insecticide, and decreases exposure to people and pets. A crack-and-crevice (C&C) tip can be inserted into narrow openings to deliver a small amount of insecticide directly to concealed surfaces. The alternative treatment method is to use a pin-stream on the nozzle. This is less efficient and more expensive than a crack-and-crevice straw, as it is more likely to result in over application. Using a pin-stream for a C+C application is not cost effective because the flow rate (8.9 ounces per minute) of the pin-stream orifice is significantly higher than the crack-and-crevice straw (2 ounces per minute).
 

Example: Using a tank sprayer and C+C straw, a technician can treat 20 linear feet of baseboard in about 1 minute. About 2 ounces of insecticide are delivered while slowly pulling the C+C straw along the inner back of the baseboard. Using a pin stream to treat the baseboard, nearly 9 ounces of liquid would be applied, and some would splash on the wall during application. The extra 7 ounces is wasted and costly.

The objective of treating behind baseboards is to create a continuous band of insecticide residue on the void surfaces. This can be done by pulling the C+C straw along the inside of the void while spraying. Treating at intervals will leave untreated gaps on the surface and provide safe resting sites for pests.

Perimeter Application. Treatments of foundation walls and perimeter soil are typically done with a backpack sprayer because of the capacity and carrying convenience. Insecticide labels may recommend spraying 1 foot up the foundation wall and 1 foot out onto the soil. This can be done with a coarse fan spray and holding the nozzle 14 to 18 inches from the wall. However, a common practice is to use a pin-to-cone nozzle. These were not designed for treating flat surfaces and have a high flow rate, which can result in over application. The objective of perimeter treatments is to establish a barrier of insecticide residue on surfaces to prevent or reduce entry of crawling pests. A fan-spray provides a linear pattern of droplets without the circular overspray of a cone nozzle and the potential of drift to non-target surfaces.

Example: Label directions specify 1 gallon per 1,000 linear feet for perimeter application. Treatment can be done with a coarse fan spray (17 ounces per minute) and a 2 mph walking pace. A cone-spray nozzle can deliver 45 ounces per minute, which is more than 2.5 times the coarse fan delivery rate. Using the cone spray results in costly over application and does not give the 1-foot-up, 1-foot-out spray pattern.

Termite Control. Over application of liquid termiticide occurs when applicators are careless with the amount applied during each soil rod insertion, or when applicators use tools without trigger- or lever-action valves and directional nozzles. Soil rodding with a nozzle that has a flow rate of 2 gallons per minute requires a treatment time of 12 seconds for a 1-foot deep foundation, and 48 seconds for a 4-foot deep foundation. The lever-action on/off control on professional valves provides precision application. Soil rods with a ball-valve control are less responsive, requiring 1 to 2 seconds for the applicator to close the valve. This extra time may seem small, but can result in costly over application.
 

Example: Treatment of a house with 160 linear feet and a 4-foot deep foundation requires 48 seconds of liquid application for each soil rod placement. This would deliver the label rate of 4 gallons per 10 linear feet, or a total of 256 gallons. Taking an extra 2 seconds to close a ball-valve would deliver 266 gallons, or an expensive over application of 10 gallons.

The efficacy of modern-day termiticides depends on establishing a continuous (no untreated gaps) and uniform (concentration) zone of treated soil around a structure. This zone can be established by using tools and nozzles that compensate for various soil conditions and reduce unnecessary and costly over application.

Baits. Gel baits are an important component of ant and cockroach control programs, but their efficacy depends on consistent application. Using modern baits requires consistent delivery of small amounts, 0.25 to 0.5 grams, to pest harborages. Precise application increases control, eliminates waste and reduces overall operator costs. However, in spite of these benefits, operators may use bait guns that deliver variable size placements, instead of guns that are adjustable to ensure delivery of the same size placement with each pull of the trigger.

Example: A technician has a 30-gram syringe of cockroach bait and a variable delivery bait gun. Four accounts must be treated, each with 15 bait placements. One syringe will do all four using the label rate of 0.5 grams per placement. But with a little more trigger squeeze, placements can be 0.7 grams. Instead of 7.5 grams total bait for the first account, 10.5 grams is placed — an extra 3 grams. The second account gets the same treatment, again with 3 grams extra. At the third account, the syringe contains bait for only 13 placements, and no bait remains for the fourth account. Applying extra bait in each placement reduced the 60 placements per syringe to 43 placements.

Precision-application bait guns deliver a consistent amount of bait with each trigger pull. This enables technicians to treat inside infested harborages and achieve better control. It is not necessary to visually monitor every placement to ensure the correct amount. The economic benefits of using precision bait guns include: less time spent on application, less wasted bait due to over application, and more effective control.
 

Dusts. Over application of dust is common in professional pest control. Applying dust is like applying liquid: a thin layer of dust on the surface provides the most effective treatment. The physical nature of dust and the concentration of active ingredients are sufficient for a crawling pest to pick up a lethal dose with only limited contact. But dust is often difficult to see on treated surfaces, which can lead to the technician applying more. Over application can be unsightly and result in exposure to people and pets, but as important, it reduces efficacy.

Dust application is made unnecessarily difficult because of product label directions. The application rates are often presented in a format that promotes over application. Dust is delivered primarily as a crack-and-crevice application. However, on product labels the application rates are typically given in grams per square yard or pounds per 1,000 square feet. This is an inappropriate scale for indoor application. The practical solution to the confusion created by product labels is to convert square yards and square feet to linear feet, and to use a hand duster with a consistent delivery.
 

Example: A dust product label recommends 2 to 3 grams per 1 square yard, which can be converted to 2 to 3 grams per 4.3 linear feet. The B&G Bulb Dust-R delivers 1 gram per squeeze. To apply dust using this duster, 1 squeeze per linear foot will deliver the high rate (3 grams), and 1 squeeze per 2 linear feet will deliver the low rate (2 grams) on the product label.

To be effective and control cost, dust application has to be consistent from one technician to the next. The use of bulb dusters is subject to the habits of individuals and features of the unit, such as operational capacity and flexibility of the duster. Overfilling the bulb and excessive hand pressure can lead to costly and ineffective application.
 

Granules. The objective of perimeter treatment is continuous coverage of granules in a zone around and adjacent to the building. Achieving this without under or over applying depends on the equipment used. Handheld fertilizer spreaders can create a wide, broadcast-type pattern, easily applying twice the label rate. A piston-type applicator is better suited for perimeter treatment, as the delivery pattern is about 1.5 feet wide by 5 feet long. Because of this narrow treatment zone, the granule distribution is relatively uniform, which increases soil coverage and the potential for encounter with target pests and decreases the potential for costly over application.

William H Robinson is an accomplished author who has written several books for the pest management industry including Urban Entomology and Urban Insects and Arachnids.