It has been more than 75 years since dichlorodiphenyltrichloroethane (DDT) was developed as the first modern synthetic insecticide. Initially used by the military during World War II for combating disease, DDT was widely used in the U.S. on livestock, in housing authorities and institutions, as an additive for dry-cleaning clothes, as an aerial spray for mosquitoes, and for use in the home and garden.

One study by the Office of Scientific Research and Development in 1947 even recommended sacks of grain be impregnated with DDT to protect stored cereals from insect infestation: A 1 percent DDT solution provided adequate protection and a 5 percent formulation provided a high degree of prevention.

DDT has been recognized as one of the 100 greatest discoveries of the 20th century. Government estimates indicate more than 500 million lives were saved from insect-borne diseases.

Silent Spring, a 1962 book by Rachel Carson, highlighted the persistence of DDT and how its continuing overuse was literally poisoning the environment. Scientific data combined with public awareness were factors for the eventual banning of DDT in the United States by the U.S. Environmental Protection Agency (EPA). Because of ongoing worldwide health concerns, global studies (2001–2014) reported ongoing production in developing nations.

The Evolution of Insecticides
During the 1950s and for the next 30 years in food handling establishments, the need for pest prevention and control was still about pesticides. It wasn’t unusual to have a drum of pyrethrins and an inventory of residual insecticides in the pesticide storage room. At that time, many food processing plants used the services of an in-house technician. Often, it was the least knowledgeable, least experienced, and lowest-paid person who was assigned the responsibility for spraying pesticides. Not until the creation of the EPA (1972) and updates to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) of 1910 were there any significant changes in regulations, policies, and procedures.

Monthly applications of a residual insecticide with a pump sprayer were common. For flying insects, flour beetles, and even cockroaches, space treatments (fogging/misting) with pyrethrins were the standard practice for prevention and control. Conventional wisdom dictated that if the fog filled the room, it was expected to solve the pest problem, at least temporarily. 

In the 1960s, organophosphates and carbamates were the residual insecticides of choice for the food industry. Wet- or fan-spraying perimeters and baseboards with diazinon, Dursban, and Baygon was common. Two theories were considered: 1) Spraying baseboards would prevent pest problems from occurring, and 2) insects harboring in cracks, crevices, and wall voids would be flushed out by the residual insecticides, and control would be achieved. Finding dead insects along the perimeter was an indicator of a successful treatment. Broad statements on pesticide labels were flexible in their interpretation: “Thoroughly treat walls and floors with special attention to cracks and crevices, corners, and perimeters.…” Overspraying and misapplications were a continuing concern.

The high volatility and odors emanating from organophosphates and carbamates, especially in an open environment, created a distinctive avenue for translocation and potential cross-contamination on bags of ingredients and equipment surfaces. Moreover, continual exposure to these toxic vapors would become a risk to the pest control operator and plant employees.

The introduction of the Whitmire Prescription Treatment aerosol with a plastic extension tip changed how insecticides were applied. Other pest control manufacturers followed with similar attachments on pump sprayers and injection equipment. Thus began the new “crack & crevice” terminology for what eventually would become a standard requirement on pesticide labels.

To target insects in those hidden locations, cinderblock walls were dusted with Drione (silica gel/pyrethrins) or boric acid. Placement of small strips of Vapona (2,2-dichlorovinyl dimethyl phosphate; DDVP) in electrical panels, conduits, and junction boxes was effective for the prevention and control of cockroaches; adding a strip to a confined space where flour and food residue accumulated provided protection from harborage and infestation by stored-product pests. Although this time-release method provided long-term control, the lingering and seepage of vapors had deleterious effects on employees working in close proximity to the treated environment.

Dating back to the 1950s, space applications were the preferred method of treatment. Monthly applications would provide immediate control of flying insects and helped prevent migration of exposed crawling insects; increased frequencies were common, if conditions warranted.

Initially used for outdoor applications, thermal fogging (e.g., Swingfog, Dyna-Fog) was introduced to the food processing industry in the late 1950s. An oil-based pyrethrin formulation was dispersed through a heating element that would generate an oil vapor similar to smoke. Although the billowing vapor provided complete coverage of an entire room, there were special concerns:

•    Dispensing an oil-based formulation with a flashpoint of 150 °F near a heating element that generated more than 700 °F was a possible fire hazard, especially in an enclosed environment. Moreover, the smoke-like fog became a potential problem for false fire alarms. City ordinances and regulations began restricting and eliminating the use of thermal foggers.

•    While the oil vapors had an excellent knockdown on flying insects, studies indicated the tiny droplets did not impinge effectively on crawling insects.

•    In addition, the intense heat reduced the toxic effects of pyrethrin by as much as 40 percent.

Because of their low mammalian toxicity, excellent knockdown, and flushing action, pyrethrins were primarily selected for misting. Dispersal of pyrethrin formulations through cold foggers, portable sprayers, air-operated nozzles, and aerosol generators delivered spray particles in a broad range of 1–50 µm. A new concept of ultra-low volume, combined with a lower dosage and a higher concentration of pyrethrin, produced uniform droplets of 5–15 µm. The optimum-size droplets were more efficient for maximum coverage and were ideally suited for critical impingement on the insect.

In the 1950s, the highly volatile insecticide DDVP became widely used for aerosol applications in tobacco warehouses for cigarette beetles. By 1970, the food industry began space treatments with DDVP for stored-product pests. With its high rate of vaporization, DDVP would readily expand into those difficult-to-reach areas: between and under pallets and around equipment. And with its excellent vapor action, it had limited penetration into cracks and crevices, and in dusty environments. Its far-reaching properties provided greater efficacy. However, with its relatively high toxicity (e.g., dermal, inhalation), personal and environmental safety factors needed to be considered: Applicators required protective clothing and respiratory equipment. Because of the possibility of absorption, there were label restrictions on certain packaging materials and ingredients. Although DDVP rapidly dissipated in the atmosphere, aeration procedures were essential. Stringent guidelines have been added on subsequent pesticide labels.

The highly volatile residual insecticides such as organophosphates and carbamates were initially replaced with synthetic pyrethroids. The introduction of cockroach baits and insect growth regulators brought a new dimension as to the mode of action and the methods of treatment. Recent industry efforts have focused on minimal-risk and other classes of insecticides. The Clean Air Act of 1963, Food Quality Protection Act of 1996, and other government regulations brought a new height of public awareness and the need for effective pest management programs.

The Shifting Focus of Regulations  
EPA shifted emphasis to the role of protecting public health and the environment. Before that, pesticide labels were quite liberal in their methodology. For many years, phrases such as “Safe to Use When Used as Directed,” “Non-Toxic,” “May Be Applied during Operations,” and “Repeat as Necessary” were listed on the label. Precautions about personal and environmental safety were minimal, at best.

While the U.S. Food and Drug Administration was responsible for enforcing pesticide tolerances established by EPA, studies had long since recognized that contamination of foods could result from pesticide usage in food handling establishments. Any misuse or applications not consistent with label directions would be a serious violation of regulations.  

Guidelines for pesticide labels became more restrictive and inclusive as to methods of application, area of treatment, target pests, quantity used, storage practices, and personal and product safety. Listed below are some of the policies, procedures, and regulatory decisions that were relevant to pesticides, pesticide safety, and pest management programs:

•    EPA Pesticide Registration Notice (PR 73-4) created the initial format for the registration of “Residual Insecticides in Food Handling Establishments.” Pesticide labels had to be clearly defined: for use in food and nonfood areas, residual insecticides, contact insecticides, space treatments, crack & crevice, spot, and general surface applications. Following label instructions was of major importance and became the benchmark for the service technician.

•    Subsequent PR Notices as well as EPA and Occupational Safety and Health Administration regulations (e.g., right-to-know, material safety data sheets, minimal-risk pesticides, National Organic Program, etc.) outlined specifications for employee safety and additional regulations for pesticide applications.

•    Between 1974 and 1980, FIFRA reauthorized the responsibilities for the education and training of pesticide applicators. State agencies were assigned the responsibility for developing separate categories for training and recertification. Federal guidelines had to be followed or more stringent regulations adopted. Recertification training programs became an industry standard.

•    The Food Quality Protection Act of 1996 established a new set of safety guidelines. Pesticides would be reassessed according to residue, tolerance levels, aggregate and cumulative risk from exposure, and other concerns. The protocols for each pesticide were extensive. Based on scientific data and in compliance with regulatory standards, pesticides would be reviewed, and if the pesticide posed a significant risk, labels would be revised and some registrations would be canceled (e.g., Dursban[1]).

Changes in science and pesticide practices occur over time, and these periodic review cycles make sure that as changes occur, pesticide products can continue to be used safely. The Registration Review Program began in 2006 with the goal of reviewing each pesticide’s registration every 15 years to make sure that the pesticide would still meet EPA standards.

IPM: Beginning of a New Era  
In the early 1980s, a new era of pest management began with integrated pest management (IPM). Although there are many definitions, IPM can be defined as prevention or suppression of pest problems through a combination of techniques such as monitoring for pest presence and establishing treatment threshold levels, using nonchemical practices to eliminate conditions that are conducive to pest development, improving sanitation, and employing mechanical and physical controls. IPM takes advantage of all appropriate pest management options including, but not limited to, the judicious use of pesticides that pose the least risk to people and the environment.

Monitoring and Inspections
With the introduction of global food safety audits (e.g., British Retail Consortium, Safe Quality Food) and ongoing regulations, now more than ever, pest management programs must be clearly defined. The service technician must have the education, communication skills, and on-site experience to carry out the duties of a pest management professional (PMP).

Equally important, a well-maintained IPM program is not just the responsibility of the PMP; it also involves the food safety manager, quality control technician, the maintenance supervisor, and the plant manager—the entire facility management team.

Monitoring, data analysis, and inspections are the cornerstone of effective pest management.  

•    A well-designed IPM program depends upon an early warning system. Trap monitoring is an ideal method for detecting and even measuring the extent of an infestation.

•    Interpreting the data from sticky traps, pheromones, insect light traps, and mechanical devices is extremely important for identifying pest patterns or sudden increases in activity. Noted entomologist Wendell Burkholder, Ph.D., is quoted as saying, “The use of pheromones and trapping procedures are not difficult. However, the timing and placement of traps as well as interpretation of the results require a good understanding of insect biology and behavior.”

•    Monitoring and data analysis support visual inspections. Knowing where the potential “hot spots” are can be a valuable asset. Most important, the PMP and the food safety team should be aware of those conditions that contribute to pest entry, attraction, and potential infestation. 

Over the past 50 years, there has been a dramatic transition in how pest management programs are now performed. With few exceptions, food handling establishments no longer have scheduled pesticide treatments. From those days of pesticide dependency, estimates indicate pesticide usage has been reduced by more than 95 percent in many food plants and warehouses. Today, IPM, pest prevention, corrective actions, and science-based technologies have the greatest impact in solving pest issues.    

Richard Kammerling is president of RK Pest Management Services. His career spans more than 40 years in devloping new pest control technologies, troubleshooting pest problems, and designing food safety and IPM programs.

1. In 2017, EPA reinstated Dursban. The final decision is in the courts. Based on the history of this pesticide and having firsthand knowledge, I believe bringing Dursban back to the food industry would not be a wise decision.