Integrated Pest Management

Denver Parks and Recreation follows a rigorous turf management schedule which incorporates proper irrigation, mowing, fertilization and aeration practices to maintain healthy turf and safe playing surfaces. High quality turf outcompetes weeds for light, water and nutrients, preventing large stands of weeds from establishing. Growing a dense, healthy stand of turf is one of the best ways to reduce weed populations and the need for herbicide applications.

Irrigation is a key component for healthy turf. DPR is committed to responsible water use and maximizes irrigation efficiency through active system management and implementation of evolving technologies. Through proper irrigation, grass builds a strong root system resulting in dense stands of turf that is more resilient to pests and drought.

Key components of IPM to grow a vigorous lawn that outcompetes weeds:

• Core aeration: perforating the soil with small holes to allow air, water, and nutrients to penetrate to the root system, helping it to grow deeply
• Slice aeration/vertical cutting: narrow slits in the soil that encourage lateral growth of turf
• Over seeding: periodic application of seed to an existing turf stand to improve its density
• Topdressing: application of a thin, uniform layer of soil or organic materials over the turf surface to improve soil properties and growing conditions while leveling playing fields when minor variations or depressions exist

By focusing on creating strong, resilient turf that outcompetes weeds for water and nutrients, most weed populations are controlled within acceptable thresholds. Targeted chemical applications are only used on turf for:

• Noxious weed control as mandated by the Colorado Noxious Weed Act
• Pest populations dense enough to adversely affect turf health and its ability to provide safe playing surfaces
• Pest populations that prevent seed germination during turf renovation projects.

A healthy tree canopy is a crucial part of a healthy city. The Office of the City Forester strives to maintain a thriving urban forest through ordinance and rule enforcement, adherence to industry standards and best management practices such as:

• Supplemental watering
• Mulching, pruning and removal
• Diversified tree planting
• Matching proper species to existing site conditions.

Pesticides are incorporated as part of the maintenance schedule when pest populations:

• Exceed Parks Standards or defined economic and aesthetic thresholds
• Adversely affect desired plant density and health
• Threaten the existence of trees or a tree species 

Thriving native ecosystems are created and protected through consistent noxious weed management and vegetative native restoration efforts. DPR is committed to managing noxious weeds through appropriate eradication, containment, and suppression programs as required by the Colorado Noxious Weed Act.

DPR’s lake management strategy prioritizes scouting and managing toxic algae blooms. Non-toxic filamentous algae that’s present in lakes throughout the park system is managed through mechanical and cultural methods including lake aerators and water column mixers, as well as chemical control through aquatic-approved algicides. The goal is to create a healthy lake ecosystem that strikes a balance between aesthetics and water health by leaving some filamentous algae to assist in beneficial nutrient uptake. This reduces food sources for potential toxic algae blooms. Learn more about lake and stream management. 

DPR follows a strong management program in specialty gardens, shrub beds and greenhouses, with IPM considered the most important tool and prevention the most effective strategy. Through design and appropriate maintenance, we reduce the landscape’s capacity to support targeted weed and pest populations. This minimizes the need for chemical application to maintains pest populations within acceptable thresholds.

Other key components of IPM in ornamental garden management are:

• Creating thorough plans that put the right plant in the right place to limit access to known pest food sources while supporting healthy plants and pollinator safety
• Mulching and mechanical removal of weeds in ornamental beds (hand pulling, hoeing, and cultivating)
• Piloting biological control for pests such as wasps, pheromone traps, companion planting, BTG “Bacillus Thuringiensis”
• Weed Burners (for greenhouse weeds, Open Space)
• Using pre-emergent to suppress persistent, known weed populations in specialty gardens, shrub beds and tree rings.
• Piloting alternative planting media (pea gravel) for perennial beds that reduce weed seeds ability to germinate

For more information on Integrated Pest Management and horticulture in the front range please visit our partners at the Colorado State University Extension Service. 

DPR's Applicator Technicians, Certified Operators and Qualified Supervisors apply chemicals according to the following schedule: 

Spring

• Granular pre-emergent application to reduce weed seed germination and reduce the need for spot spraying in tree rings, plant beds, and other mulched areas
• Selective spot spraying for noxious weed control in Open Space 
• Selective spot spraying as needed in hardscape cracks and tree rings
• Turf grub control 
• Emerald Ash Borer, Ips Beetle, Kermes Scale, European Elm Scale, Mountain Pine Beetle, Gambel Oak Borer, and Fireblight prevention and control in trees
• Tree Growth Regulators for trees as needed

Summer

• Beetle control in flower/rose beds
• Selective spot spraying of weeds as needed in hardscape cracks and tree rings 
• Selective spot spraying of broadleaf weeds to provide control prior to turf restoration projects
• Selective spot spraying of noxious perennial weeds typically found in Open Space and riparian areas
• Ips and Mountain Pine Beetle prevention and control for trees as needed
• Selective algae treatment in lakes and waterways

Fall

• Broadleaf weed and grub control in turf, Open space, and plant beds
• Selective spot spraying of noxious perennial weeds in Open Space
• Pre-emergent applications for noxious winter annuals in Open Space
• Tree growth regulators for trees as needed

Winter

• Selective spot spraying for noxious weed control in Open Space
• Pre-emergent applications for noxious winter annual weeds in Open Space
• Cut-stump treatments for woody invasive species
• European Elm and Kermes Scale prevention and control in trees

Yellow Notification Flags

Prior to application, yellow pesticide notification flags are placed at every entry point to the area where selective treatments will occur. DPR staff follows the Colorado Pesticide Applicator’s Act rules for pesticide notification sign content and placement.

• Flags do not indicate that the entire area or entire park is being treated
• Applications are focused only on the areas where the target pest is located
• Flags are removed in accordance with the product label’s re-entry interval. The product label is federal law, and determines the amount of time needed after application that flags must be in place to notify the public
• For most products used in parks, the re-entry interval coincides with the product’s dry time
• Flags are removed after the re-entry interval has passed

Buffer Zones

Buffer zones are areas within parks where chemical applications are not used to control pest populations. Buffer areas may be closed and posted prior to pesticide application if control of invasive weeds is required by the Colorado Noxious Weed Act.

Buffer zones include:

• Playgrounds
• Picnic sites
• Workout stations
• Within fenced dog parks unless dog park is posted closed
• Within swimming pool fences and splash pad areas when operational for the season