The City of Boulder was one of the first municipalities in the country to create an Integrated Pest Management program and policy. This effort was initiated by city ecologists and vegetation managers and reflects the city’s commitment to environmental stewardship.
Integrated Pest Management (IPM) is a process that is used to address pest issues, while minimizing risks to people and the environment.
What is Integrated Pest Management or IPM?
There are a number of definitions and approaches to IPM. “Integration” is the key element of IPM - using a combination of approaches. A series of steps are taken to determine whether an action to control a potential pest makes sense, while considering the underlying reasons why an organism is a pest in the first place. Once a pest issue reaches a threshold where city staff decide to take action, they balance the risk that the pest poses with the potential impacts to both the environment and peoples’ health from practices that can be used to control it.
What is a Pest?
Broadly, a pest is an organism that interferes with desirable plants, impacts human or animal health, damages structures, or harms some component of the ecosystem. The pest can be an insect, rodent, nematode, fungus, weed, or any other form of terrestrial or aquatic plant or animal life or virus, bacteria, or other micro-organism.
How is a Decision Made to Treat a Pest?
IPM uses a commonsense approach to decision-making, based on the best available science, as well as observation and knowledge about the biology of the target organism. This is all then viewed within the context of how a potential pest impacts an ecosystem. It is a "whole systems approach,” which selects, integrates, and implements a combination of strategies.
Pest prevention is the foundation of IPM. Often, a combination of approaches is necessary. The IPM process categorizes management practices and places them within a hierarchy. The lower categories are considered to be the least impactful or risky interventions. However, this process can be quite complex since any intervention can have unintended impacts. A successful ecosystem management or ecological IPM approach requires continuous information gathering, and often results in the city’s expert staff developing new or site-specific approaches.
Many times, the most environmentally sound management practices will keep pest populations within acceptable levels. When non-chemical approaches fail or are not feasible, then judicious use of pesticides is considered.
The IPM Hierarchy - Management Categories
Prevention
Prevention is the foundation of successful IPM. It reduces the capacity of the ecosystem to support target pest populations through design and appropriate management. Examples include choosing plants that are part of the natural ecosystem for that specific site, using weed-free soil, taking care to prevent introduction of exotic organisms, building healthy soils, and protecting and enhancing biodiversity.
Cultural Control
Cultural control are practices that reduce pest survival, reproduction or establishment through enhancing desired conditions. Examples include increasing grass mowing height to shade out weeds, managing irrigation to reduce fungal diseases, or securing trash to avoid rodent problems.
Mechanical Control
Mechanical control uses physical methods or mechanical equipment to remove or exclude pests. Examples include mowing, goat or cattle grazing, hand removal of insects or weeds, barriers and traps. Some forms of mechanical control may be harmful to a sensitive site, and like all other interventions, must be thoughtfully considered within the overall context of each particular site.
Biological Control
Biological controls can include the introduction or enhancement/attraction of natural enemy organisms of target pests. Introduction of non-native biological control organisms carries potentially high risk and must be thoroughly assessed before consideration.
Biological control occurs naturally in healthy ecosystems and keeps organisms in balance. This is why pest prevention in IPM is such an important and foundational part of ecosystem management.
Chemical Control
Chemical control or pesticides are a last resort when other management practices have failed or aren’t feasible. Before pesticides are approved for use, City’s IPM program requires the screening and assessment of pesticides for potential human and/or environmental impacts.
How Does the City Use Pesticides?
What is a pesticide?
Many people consider the terms pesticide and insecticide to be interchangeable. However, an insecticide is one type of pesticide. A pesticide is defined as any substance or mixture of substances that are intended to kill or repel any pest. In addition to insecticides, this also includes herbicides, fungicides, rodenticides and any other substance that is used to control any pest. Just like synthetic chemicals, organic pesticides are also regulated by the Environmental Protection Agency and must be registered by the Colorado Department of Agriculture to legally apply anywhere in the state.
Stewardship of City Lands
Any management decision is a series of trade-offs that depend on the objectives for each site. City staff must balance time and resources, and the risks that a pest poses to the environment and public safety, along with the risk and costs of an intervention to manage a pest. In most instances, the city uses non-chemical practices to manage city properties. All managed turf grass and landscaped beds are managed organically.
The majority of natural land in the city is managed by cattle and goat grazing, weed pulling, prescribed burns - and managing ecosystems by encouraging and managing native plant communities and wildlife. On some occasions, city staff do choose to apply pesticides, mainly herbicides, to manage weeds. Staff are mandated by state law to control and eradicate certain weed species, and some sites in more rugged areas are inaccessible and not possible to hand pull or dig out weeds.
The city has a rigorous pesticide assessment process before application is permitted on city-owned properties. Only approved pesticides can be used. The IPM program requires staff to use a decision-making process to determine where and how to apply a pesticide or herbicide when it is needed in order to minimize unintended effects to people, non-target organisms, surface and ground water and overall environmental health.
If you see a pre-notification sign posted for a pesticide application, or check the city’s Pesticide Dashboard below to find out where a pesticide is going to be used, it’s important to keep in mind that almost all pesticides and herbicides are spot-applied – many times to just a few weeds or applied in a thin ring around the outside of stump after an invasive or hazardous tree is removed. Applications for emerald ash borer (both organic and synesthetic) are injected into the tree. Even natural products like the mosquito larvicide, Bti, are used in a very targeted way to reduce potential ecological impacts.
If you’d like to learn more details about IPM and city’s program, visit this series of story maps.