Role of Action Thresholds in Your IPM Program

Published in the June 2013 Issue Published online: Jun 02, 2013 Tom Calabrese Principal hydrogeologist with EnviroLogic Resources, Inc. in Portland, Ore.
"Distribution of ground cover to assist in determining percentage cover. Bureau of Rural Sciences. Source: Bayley (2001)
"Charts for estimating mineral grain percentage composition of rocks and sediments. (Modified from Comption, 1962)

Action thresholds are the critical piece of the Integrated Pest Management puzzle, in my view.

How you define your action thresholds will drive the way you use pesticides and interact with the environment.

Action thresholds also define the maintenance standards required by your clientele. This article will show you the importance of defining action thresholds within the context of a written IPM Plan.

So, what is an action threshold?

I define an action threshold as the point at which its time to make a pesticide application to address a given pest or disease. If you have not reached your defined action threshold, then by definition, it’s not time to spray. Pest populations present up to this defined action threshold would be addressed using your cultural practices bag of tricks—fertilization, aerification, hand weeding, etc. If you are making pesticide application based on a calendar, you are not using an action threshold and could be needlessly wasting expensive pesticide products.

Action thresholds are numeric values that describe an unacceptable pest population. They need to be measurable and objective. Action thresholds  are pest-specific and area-specific.

You may have multiple action thresholds on your golf course for the same pest or disease because you manage certain areas to different maintenance standards.

The point at which it’s time to make a pesticide application can be defined in almost any units that make sense to you. For example, common units for defining action thresholds include percentages, as in percentage of an area affected; weed plants per thousand square feet in a fairway turfgrass stand; or larvae per square foot beneath a putting green.

Other units may make sense as well. Growing degree days are a good set of units for many pests and, while based on a calendar, are really more tied to a developmental feature of the pest that can be beneficially disrupted at a certain time.

A combination of temperature and humidity can also be used as an action threshold in your IPM Plan. For example, you can define a forecast of 90-degree temperature and a 90 percent overnight humidity as an action threshold for a preventative fungicide application. You should use any combination of units in your IPM Plan that define the action thresholds for specific pests or diseases.

Action thresholds should be defined for each management area on your facility. You will likely have different standards of care for turfgrass in a fairway versus the putting green or rough.

An infield may be managed differently than an outfield. Natural areas and bioswales would have different standards than common areas around the clubhouse. And ornamental beds would likely have another standard.

So, your first step in defining action thresholds is to define the management areas of the golf course. Each area that has its own management characteristics— mowing height or frequency, fertilizer requirement, or irrigation requirement—should be defined. For example, putting greens can be classified as one management area because they are all managed using the same maintenance standards. Similarly, tees, fairways, approaches and roughs may all be grouped into management areas with the same maintenance standards throughout the facility.

The next step is to define all the pests and diseases that are present on the golf course because each will have a different action threshold. A certain pest or disease may be present or of concern only in a few of your management areas but it’s the complete listing we are after at this point.

Now that you have your management areas defined and can enumerate all the pests and diseases on the golf course, it’s time to define the action thresholds. Remember, the action threshold is the pest population that triggers you to make a pesticide application.

Action thresholds are not triggers for cultural practices. Each pest or disease in each management area will have its own action threshold.

As you go through this process, you may find that action thresholds for some pests are not applicable throughout the facility. Pests or diseases that need to be treated with pesticide on a putting green may be cured through cultural practices in other management areas.

Action thresholds are specific to a particular facility and should be designed to meet the maintenance expectations of the clientele at that facility.

That’s not to say two different facilities can’t use the same action thresholds— many facilities share common action thresholds. But they can be different and should match the way the superintendent thinks.

All this information may have resided in your head as a superintendent that has been managing a particular facility for a long time. Unfortunately, that institutional knowledge and memory is difficult to communicate to members, management and the outside world.

Your staff may become accustomed to the way you think over time but the may miss many of the nuances such as,

“What is the numeric action threshold you are going by to decide to make that pesticide application?”

You need a way to document your action thresholds and how you manage the golf course. An easy way to document your IPM Plan is to use the online tools at www. Not only can you design your IPM program, best management practices covering a variety of topics can be documented using the BMP Generator.

Taken together, your IPM Plan and BMP documentation describe the foundation of your environmental stewardship program. In addition, the documents created are suitable for distribution to management, the Greens Committee, or regulatory agencies.