Integrated Pest Management

Contact Information
Parks and Trails
1055 South Grady Way
Renton WA 98057

An effective Integrated Pest Management (IPM) Program requires identifying and monitoring pest populations, and then selecting the most effective control methods. Those methods include biological, cultural, mechanical and chemical controls.

City of Renton park employees are licensed pesticide applicators through Washington State Department of Agriculture and are required to complete 40 hours of continuing education over the course of each five-year certification period.  

Alternatives to Chemical Control Used

The Parks and Recreation Department considers alternatives to managing pests. Power sweeping trails, hand pulling weeds, flame-torching weeds, using weed barrier fabrics, and applying wood mulch to landscape beds are some of the mechanical methods used to control plant pests.

Parks and Trails Division utilizes best management practices and has tested different weed barrier fabrics for effectiveness, generally installed as part of trail construction projects. Staff prune caterpillar nests from vegetation when they become concentrated and pose threats to trees and shrubs and, an example of biological control, the City has used ladybird beetles to feed on tree aphids

When and How Chemicals are used

Herbicides are generally used on all actively managed park and trail areas. Of the 1,227 acres of parkland, 542 acres are actively managed. Herbicides are used seasonally, as need is determined, in shrub beds and on turf areas. When spraying occurs, areas are posted with notification signs. A systemic insecticide (taken up by tree roots instead of sprayed) is used to control aphids on downtown street trees.

Herbicide applications are applied to specific areas in their entirety or as spot treatments. An application to an entire planting bed helps deter weed growth and can lead to fewer applications through the rest of the season.  Spot spraying is used when a population of weeds is manageable by this individual treatment.  Spot spraying reduces the volume of chemical used and helps minimize environmental impacts.

Maintaining Parks, Trails and Open Spaces

Integrated Pest Management is the strategy used to maintain parks, trails, and open spaces. Parks Maintenance staff monitor park conditions. When pest problems increase beyond tolerable levels, they may employ several strategies to reduce specific problems. Quality Level 1 areas have a lower tolerance for pests; higher tolerance is allowed in sites designated as Levels 2 and 3, as described in the Parks Maintenance Operations Manual.

Practices used to reduce pest problems include:

  • Plant appropriate vegetation and maintain healthy ground covers, shrubs, and trees;
  • Conduct soil tests and modify soil conditions with compost, mulch, and fertilizers to promote healthier plants;
  • Provide adequate moisture;
  • Cultivate plants using topdressing, soil aeration, and soil slicing equipment;
  • Proper pruning of shrubs and trees to increase air circulation and remove dead and diseased branches;
  • Maintain proper turf heights and use grass-cycling (grass blades left on turf);
  • Use of bird repellent sound equipment and dogs to chase nuisance birds,
  • Bark mulch shrub areas and trees. Mulch conserves moisture, reduces weeds, and protects vegetation;
  • Physically remove pests using hand labor, implements, and power equipment.


The city looks to local, state, and federal laws and regulations with respect to maintenance activities in general, and to chemicals specifically. Other IPM information is available through the following websites, or by contacting the Parks and Recreation Department at (425) 430-6600 or [email protected]

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