SECTION 3: Introductory concepts in the study of Integrated Pest Management (IPM)
3.1 The Ecological Basis of Pest Management
Integrated pest management, or IPM, is the use of a combination of pest control strategies in an environmentally, ecologically, and economically sound manner to maintain pest populations below a designated level (threshold).
Control strategies used in IPM programmes include physical, mechanical, and cultural techniques; biological control through natural enemies; modification of pest behaviour with pheromones; and the judicious use of less toxic or selective pesticides.
Central to any IPM programme is the concept of a “threshold” – this refers to the pest population level below which control actions are not implemented. In agriculture, IPM programmes employ a threshold known as the “economic injury level.” When the number of pests is below that level, it may cost more to control the pest than what the part of the crop lost to pest damage is worth.
But before we go on, let’s have a look at a few useful definitions.
- Economic Damage a level of damage caused by insect activity that can be measured as an economic loss.
- Economic Injury Level (EIL)
- Point where pest suppression becomes economically justified.
- Level of damage or insect abundance capable of causing damage equal in value to the cost of suppressive measures.
- Lowest population density that will cause an economic damage level that is no longer tolerable.
- Economic Threshold (ET) level of damage or pest abundance that indicates a problem and allows time to take suppressive measures before the EIL is reached, also called action threshold. Lower than the EIL, density at which action should be taken to prevent the pest population the EIL.
- Carrying Capacity the maximum population size an environment can support. Different environments have different carrying capacities.
- Integrated Pest Management (IPM)
A strategy of pest containment that seeks
to maximize the effectiveness of biological and cultural control
factors, utilizing chemical controls only as
needed and with a minimum of environmental disturbance.
- Has preventative and reactive components.
- An ecologically based system in which all available techniques are evaluated and consolidated into a unified programme to manage pest populations so that economic damage is avoided and adverse side effects on the environment are minimized (National Academy of Sciences 1969).
- A strategy of pest containment that seeks to maximize the effectiveness of biological and cultural control factors, utilizing chemical controls only as needed and with a minimum of environmental disturbance.
- An organism in conflict with man as a result of the pest’s normal activities.
- An organism that reduces the availability of some resource valued by humans such as a commodity, health, or aesthetic pleasure.
- An organism that competes with man for resources or that attacks man.
- Population Dynamics is the branch of ecology that studies the structure and dynamics of populations.
Unconstrained Population Growth:
Growth as normally seen under artificial conditions, e.g. lab populations
Population Growth with Constraints:
Two populations, one showing a gradual decline in growth rates (red line), and the other showing an abrupt population crash as the carrying capacity is neared (blue line). The population crash occurs because of constraints to further growth.
Environmental resistance to growth may be because of:
- Food and shelter limitations
- Competition and predation by other organisms
- Unfavourable physical conditions
Natural Populations Fluctuate Between Upper and Lower Boundaries Over Time
Natural population size varies from year to year but the fluctuations remain within upper and lower boundaries. The upper boundary represents K.
3.1.3 Biological Growth Potential of Insects
Population size is a balance between:
- Biotic potential (reproductive capacity) of the species. (Often extremely rapid logarithmic growth).
- Environmental resistance to population growth. (Either population density dependant or independent).
Most insect species are not pests. It is estimated that at most 1% of species are pests. Natural control prevents the other 99% from becoming pests.
- Natural - direct pests of man
- Parasites and vectors of human disease
- Artificial - pests as a result of human activity
- Crop pests
- Nuisance, aesthetic pests
3.1.4 Pest Control
220.127.116.11 Management Strategies
Options to take into consideration when managing pests are the following:
- Exclude the pest.
- Eradicate the pest.
- Control the pest through population manipulation.
- Remove water and food sources.
- Do nothing.
18.104.22.168 General Tactics (Applied to strategies 1 to 4)
- Regulatory procedures.
- Biological control.
- The purposeful use of organisms (predators, parasites and pathogens) to limit pest population size.
- Designed to prevent pest population from reaching economic size.
- Genetic plant resistance.
- Designed to prevent pest population from reaching economic size.
- Cultural control.
- Reduction of pest damage or numbers through the purposeful manipulation of normal farming practices, i.e., tillage, burning, rotation, planting - harvest date, and trap cropping.
- Insecticidal control.
- Action taken to minimize damage when pest population is at the economic threshold.
- Sometimes used as a preventative measure without knowledge of pest population size.
In most cases, the potential risk associated with an insect is related to: its population density, host susceptibility, and environment.
In theory IPM is centred on the use of biological control, plant resistance to insects, and cultural controls. It employs intensive monitoring and the judicious use of pesticides. The point where pest suppression becomes economically feasible is the economic injury level (EIL).
3.1.5 Economic Injury Level
As said before, Economic Injury Level (EIL) is the point where pest suppression becomes economically feasible in terms of cost/benefit. It is where the cost of treatment is equal to the value of the loss.
To calculate the value of a yield loss, you need to know the:
- Damage potential of the insect (damage or yield loss per insect [kg/hectare]).
- Value of the crop loss (R/kg.).
The EIL is about the cost and benefit of making a treatment.
- A cost/benefit ratio of 1 is the EIL.
- A cost/benefit ratio of < 1 is an even better return for the cost of treatment.
- A cost/benefit ratio of > 1 is a loss of money. You will spend more than the return is worth.
But normally, the EIL is given as a number of insects; insects/plant, insects/area, or insects/trap. Sometimes it is given as an indirect measurement of insect activity such as percent defoliation.
The difficulty is in accurately estimating the number of insects and relating that number to a yield loss. It is impossible to count all the insects so a sampling system is developed as a compromise between accuracy and time or difficulty. If the sampling is not sufficiently accurate the information is useless and if it takes to long or is too difficult, it won't be used.
The point where the level of damage or pest abundance indicates a problem and allows time to take suppressive action before the EIL is reached is the economic threshold (ET).
A trigger point at an insect density below the EIL is the economic threshold (ET). It is when a treatment should be taken to prevent the insect population from reaching the EIL.
Insect Sampling Done to know that damage or the insect population is at the ET. There are two methods of sampling:
Absolute method - determine the density of insects per unit (acre, plant).
Relative method - indication of insect abundance or damage relative to other times or locations.
Why is sampling so important? The routine use of controls without regard to pest density is:
- Economically wasteful.
- Unnecessarily environmentally hazardous.
- Destroys natural enemies and other beneficial insects.
- Toxic contaminants.
- select for insecticide resistance.
3.2 Industry Trends and Protocols that impact on IPM
3.2.1 Trends and debate
Integrated Pest Management! - has any term created so much confusion, uncertainty or diversity in interpretation in the pest control industry? If you spent a few days searching a variety of literature - including industry magazines, newspapers, government publications and regulations - you would discover as many definitions of IPM as there are mentions of the acronym "IPM."
Where does all this leave the typical pest management service professional, out on the streets daily, trying to serve his or her customers’ needs? Why should these professionals care about the latest definition of IPM, especially when surveys show the general public has no clue what IPM is and what the term means? It’s difficult to get excited about something when the most important people to your business - your customers - don’t care about it. Your customers are interested in the bottom line - keep their building free of pests.
Still, our industry needs to start caring because special interest groups and governmental regulatory authorities are pushing the IPM agenda with one goal in mind - the ultimate restriction and possible elimination of pesticide use in the urban environment. When one tactic fails, another is formulated to take its place. As with most regulations, those involving IPM commonly contain unclear language and generally place the greatest burden on pest management professionals to accomplish the goals of IPM. This happens despite the fact that building owners bear the greatest responsibility and pest management professionals have little authority to dictate the changes necessary to minimize the need for pesticides.
The most significant debate revolves around pest control in schools and public buildings.
For example - most school systems still purchase pest control services via a process that typically accepts the lowest bid regardless of the outlined pest control specifications in the bid. Will the winning company have the time to analyze the pest control needs of the school and prepare the detailed reports necessary in accordance with the principles of IPM? Even so, will the school have the money to implement the recommendations of the professional? Many highly competent, IPM-practicing companies do not even bother to bid schools (and similar institutions) that acquire services via a low-bid process. The investment of time holds little promise of real return.
IPM has its greatest success only in those institutions and businesses committed to investing both the time, money and resources to making IPM work. Such institutions and companies realize the value of their pest management professional lies not in how inexpensively he or she can complete the service but in the knowledge and experience he or she has to analyze their pest control situation and make reasonable, practical recommendations. A spirit of cooperation is inherent in these relationships where both parties accept their share of the responsibility to achieve the goal of a pest-free building while minimizing the need for pesticides.
One overriding theme, however, from special interest groups and government bodies historically antagonistic to pesticide usage, is their thinly veiled goal of complete pesticide restriction. Common sense and science often does not make much of an impression in suggested practices and regulations.
A prime example is the exultation of boric acid as the "safe" alternative to commonly used synthetic pesticides. Not to disparage boric acid - it is an excellent and much-needed material - but its LD50 is much lower (i.e. higher toxicity) than that of many products at the end-use rate (e.g., liquid dilution or bait). The truth is that any product can be misapplied, but if the product is applied to specific locations where a pest resides, risk of any kind to building occupants is minimal at best. Boric acid may be the most misused product when in the hands of some individuals, such as homeowners and school custodians, who have no training in pest control and pesticide handling.
3.2.2 Using Pesticides
Some situations might call for extensive use of pesticides while others require little, if any, treatment. In every case, however, they must be used judiciously by applying them where they will achieve the best results.
Is it possible to eliminate a pest infestation without using a single pesticide application? Well, yes…depending on the situation. For example, a minor mouse infestation can be eliminated using traps or a fly infestation can be controlled via improved sanitation and exclusion. Reality, however, demonstrates applications are needed in varying degrees for various pest infestations. It is the professional who must investigate, analyze and decide which techniques - chemical and/or non-chemical - will solve the infestation to the customer’s satisfaction. Despite the contention of many IPM enthusiasts outside the pest control industry that "action thresholds" be enacted for each pest, the fact remains that the typical citizen demands action when even one pest is seen. Tolerance of pests of any kind is minimal, even in schools and public buildings. Does "action" mean pesticide application every time? No…but more often than not, some type of application is warranted. To believe that anyone can achieve zero pests without the use of pesticides is short-sighted.
22.214.171.124 What is the role of pesticides in IPM?
To meet the basic principle of IPM that pesticide use be minimized, one must focus first on the underlying causes of the pest infestation. Information is critical and acquiring such information can be time-consuming, especially the larger and more complex the building. This process is even more difficult when approaching service for the building for the first time.
- A critical first step, prior to inspection, is to analyze past pest control service records and pest-sighting logs, if they are available. The more months or years of records, the better the overall conclusions for planning pest management services.
- It has been our experience and belief that every building has its historic pest-infestation issues. This fact is especially true for larger buildings. A significant amount of the space in buildings will rarely, if ever, require pest control services, yet building managers often insist that every part of a building be serviced regularly. Why?
- By using past pest control records and plotting pest activity on floor plans of the facility, one can determine the highest risk areas for activity. Most areas of the building can be placed on an as-needed or less frequent service basis, permitting the service professional to concentrate efforts on the key sites where activity is anticipated. Additionally, such high-activity areas must be investigated to determine the underlying causes for the high activity in the area. If such causes can be discovered and corrected, it is easy to see where pesticide use can be reduced dramatically.
Effective IPM programmes require continued analysis based on current pest activity information. IPM is decision based, meaning the service professional determines the steps necessary for each pest situation, no matter how small. Monitoring is important, but it can be practiced to such an extent that it is detrimental to the success of the overall programme. Monitoring should be confined to those areas where pest activity is possible but not in areas requiring regular close inspection. Monitoring traps are too often placed throughout a room or building with little thought given to the trap’s true purpose.
For example, a classroom might be the recipient of a half-dozen monitors. Has the classroom ever had previous mention of activity? If so, what type of pest and where would it likely have originated? Placing traps requires they be checked - which means an investment of time - time that might be better spent elsewhere. Place each monitor with a goal in mind - to target likely activity involving the key pest. Areas with little risk of pest activity typically do not need monitoring, especially on a regular basis.
126.96.36.199 Limiting Pesticides
All the above-mentioned steps have one goal - to pinpoint active pest harbourages. Only once the site (or sites) where a pest resides is known will the decision to use a pesticide be necessary. The first questions that must be asked are whether the infestation can be controlled or eliminated using non-chemical means and what effect such efforts have in minimizing the need for pesticides.
For example, a population of German cockroaches in a school kitchen or classroom may be greatly reduced by vacuuming, but this step will not result in eliminating the infestation. Bait application will likely be necessary as well as treatment of certain wall voids with an inorganic dust product. By vacuuming, considerably less pesticide is needed to achieve the desired result of zero cockroaches. The use of baits, instead of residual products, further reduces the amount of insecticide used because baits are applied in small amounts directly into cockroach harbourages. Residuals may require treatment of a greater number of cracks and voids than is needed when using a vacuuming/baiting approach.
Another example might involve the sudden appearance of black vine weevils in a company hallway and offices. The weevils are originating in the ivy used in the landscaping outside these areas. Weevils inside can be removed by vacuuming. How they are entering the building must be determined and steps must be taken to exclude the weevils. Short-term treatment of the ivy will halt the weevil invasion, but long-term, the company must be convinced to remove the ivy completely and change the landscaping to an alternative planting.
To sum up - often, pesticides are necessary to remedy an existing or new infestation of pests. Following this step, the conditions creating the infestation must be addressed. If not, additional treatments will likely be necessary. Preventive applications (e.g., perimeter treatments) have little place in IPM. It makes little sense to attempt to treat everywhere a pest might show up. IPM dictates that the service professional focus on discovering where pests are active outdoors or might otherwise gain access to the building and then take appropriate steps, including treatments, if necessary.
Some situations might call for extensive use of pesticides while others require little, if any, treatment. Service professionals must be prepared to gather and analyze pest-related information and then make appropriate decisions regarding treatments. Pesticides have a significant role in structural integrated pest management. Let no group or person try to convince you otherwise. Pesticides must also be used judiciously, however, by applying them where they will achieve the best result.
3.2.3 Barriers that could impact on IPM
There may be barriers to implementing an IPM programme. Barriers may include the following:
- Some facility managers may perceive IPM as expensive to implement. In some cases this may be true, especially if maintenance and pest problems of the past have been ignored or dealt with improperly. Costs must also be measured over a period of time. While they may rise initially, overall costs will go down with an effective programme.
- In most facilities, pest control is often seen as the responsibility of one individual. However, factors which contribute to pest problems are often under the control of other individuals who may not think in terms of how their activities affect pest populations. For instance plumbers, electricians, gardeners and custodians all have a role in managing pest problems. Training, cooperation, and coordination are keys to a successful IPM programme.
- Even when individuals are trained and informed of their roles in an IPM project, they still may not care or feel that it is their responsibility. Everyone who has a role in IPM must be committed and accountable.
- IPM is relatively new to decision-makers using commercial pest control services. These persons may not know what considerations to take into account when issuing purchase orders, making budgets, and sending out requests for proposals (RFPs).
- IPM requires more skill and knowledge than traditional pest control, so some pest control contractors may not be up to the task of implementing IPM.
- Price is often used as the sole criteria by which pest control contracts are awarded. This often forces contractors to do the “bare minimum” and ignore many aspects of IPM. RFPs and contract proposals must contain language, which addresses specific elements of IPM.
- IPM requires a degree of participation from tenants and others who use buildings. In the past, these persons may have had a passive or nonexistent role in the pest management activities going on around them – and may even show resistance to change.
- Lack of education on IPM by Facility Management Staff and facility occupants contributes to lack of public participation. This results in little incentive to participate in the IPM programme.