The concept of IPM was first developed in production agriculture in the 1960s and early 1970s, when many pesticides had been developed and were being used on food crops. The pesticides were expensive, some of those pesticides were quite toxic to vertebrates, and there was an increasing awareness of the potential environmental issues that could develop with recurrent pesticide applications. There was considerable pressure to develop production systems that relied less on pesticides.
Scientists at land grant universities began to conduct studies, intentionally infesting (or inoculating) a crop with an insect or pathogen in several different densities and growing identical blocks of the crop without the pest present. They would harvest the crop at the end of the season from each of the “plots” and compare the yields of the pest-free crop with the crops that had been infested at different densities. At the end of the experiment, they could determine how much the yield declined as a result of a given infestation level (e.g., how many caterpillars per plant would reduce the yield by a specific number of pounds). They could then calculate how much it would have cost to apply a pesticide to reduce the pest to a level that would result in the higher yield.
The backbone of the agricultural IPM approach was identifying the “economic injury level” – the point at which the anticipated loss of yield as a result of the anticipated pest damage would be greater than the cost of the management strategy (often a pesticide application). The calculation included the cost of the product, the wear and tear on equipment, labor, and other costs related to the application, so it was primarily an economic decision. It was essentially a numbers game. In a way, the early IPM programs were a form of “does it pay to spray”.
The challenge in developing an IPM plan for golf courses is determining the value of the turf. Economic injury levels don’t really make sense on managed turf – other than commercial sod farms – because it is impossible to put a dollar figure on the loss of yield. How many grubs – or dollar spot marks or dandelions - does it take to result in a reduction in the number of rounds played? That is virtually impossible to determine.
IPM programs in managed turf usually use a concept known as “tolerance levels” or “action thresholds” to determine whether control strategies need to be implemented to reduce a pest population. Thresholds need to be site-specific, and often vary from one part of a golf course to another. Certainly, thresholds are different on greens (most intensively maintained) compared to fairways or roughs. Areas that are in view from the clubhouse are sometimes maintained a little more intensively for aesthetic reasons. More information on setting thresholds is available here.
It is difficult to set thresholds without being able to monitor pest populations. If you do not know how many insects or weeds or disease spots are present, it will be hard to predict how high the population might get later in the season. So, monitoring pest activity regularly is a key aspect of an IPM plan. More information on monitoring (scouting) techniques is available here.
The first step in an IPM plan should be to conduct a site assessment. This involves a review of the entire property, and should be site-specific. Often a course will have certain “indicator greens” where problems usually appear before they do at any other location. The site assessment should identify the various underlying conditions that might lead to the pest activity throughout the property, including the indicator greens. More information on site assessment is available here.
Stress management is a key component of IPM. Basically, turf often can tolerate one or two stresses (e.g., low mowing height, low fertility, compaction, overwatering, reduced fertility) but begins to suffer when a third or fourth stress is introduced. For example, white grub populations can be as high as 20 grubs per square foot without visible damage if the area is maintained at a relatively high mowing height, receives adequate water, has minimal traffic, and is free from predators that feed on grubs (e.g., skunks, raccoons, certain birds). But if the turf is mowed at fairway height, receives little irrigation or rainfall, is subject to golfing traffic throughout the day, and is in an area where predators are active, as few as five grubs per square foot might result in visible and disruptive damage. Providing optimum growing conditions can reduce overall plant stress, and sometimes results in the turf being able to tolerate some pest activity without showing visible signs of stress.
The IPM plan comes together as you identify and optimize management options. Those options should include agronomic manipulations (e.g., fertility programs, mowing heights, mowing patterns, irrigation practices, water quality) that minimize agronomic stress on the turf plant, and that may increase the tolerance level and therefore reduce the need for pest control. If the pest population is already above the tolerance level, or past experience suggests that it will eventually exceed the tolerance level, you may need to incorporate practices designed to reduce the pest population directly. In some cases, this will mean using a pesticide, but sometimes a biological control option may be available.
An IPM plan does include the use of pesticides, but normally the turf manager should consider all other options (cultural manipulations, biological control, renovation) before using a pesticide. If a pesticide is necessary, an IPM plan should try to identify the product that will be least disruptive to the environment. This includes considering the environmental characteristics of the pesticide (e.g., solubility, tendency to adsorb to soil or organic matter, toxicity to vertebrates, toxicity to other non-target organisms, persistence) and choosing a product that is least likely to move to groundwater or surface water, or cause harm to vertebrates or other non-target organisms. More information on the environmental fate of pesticides is available here.
One of the aspects of IPM that is sometimes overlooked is evaluation. Did the pest population really decline as a result of the steps you took? This, of course, means that you must measure the density of the population before you take action, so you can compare the initial population with the subsequent population. Evaluating management efforts documents the effectiveness (or lack of effectiveness) of the practice, and helps determine whether the cost of the strategy was acceptable for the level of control achieved. Be sure to keep notes of the conditions at the time of application – including wind speed and direction, humidity, soil and air temperature, cloud cover, temperature and pH of the water in the tank, a list of all the products that were in the tank mix, and how much rain or irrigation fell in the 48 hours after application. This may help you identify things that might have contributed to a reduced level of effectiveness from what you had expected.
Record keeping is a part of evaluation. Identify ways to record the observations that are made by any crew member who is involved with monitoring the property. You can use score cards or place mats that have a map of the golf course, and have the crew member indicate areas where they notice problems. You can print out maps of the irrigation or drainage system and create overlays representing disease or insect or weed activity. You can use drones to photograph the property and then use those images to indicate where pest activity or an agronomic stress is indicated. You can download images from Google Maps or a similar satellite-generated mapping system. Pesticide application records are a vital part of an IPM plan, as well. Be sure to include comments on those records as to the effectiveness of the application, so you can check months or years later and see which approaches were most effective.