A basic feature of an IPM program is treating pests only when they are present in damaging numbers or are likely to be later. This presence or prediction of presence is based largely on finding the pests in the turf and estimating their population sizes. This process of finding, identifying and counting pests is called scouting.
Scouting relies on personnel who are able to identify pests and know the pest habits. Scouting may occur more often than fertilizer and pesticide treatments, adding to the cost of the operation.
Pest Detection and Diagnosis
Turf areas should be scouted every other week or at least several times a year to detect important weed, disease and insect pests. The use of pest-prediction software models (forecasts), based on local weather conditions, can help the turf grass manager anticipate and prepare for various pests.
Different diseases are detected at different times of the year, as described in the key in the turf diseases chapter. Checking for cold-weather (32-45 degrees F), cool-weather (45-60 degrees F), warm-weather (60-75 degrees F) and hot-weather (>75 degrees F) diseases requires several scouting periods in the spring, summer and fall. Although a disease may be located and identified, it may be too late to treat with a fungicide. However, record the disease location and other conditions (such as weather or drainage) that probably led to disease development and implement corrective cultural practices, which could include purchasing and applying preventive fungicides if similar conditions occur again.
Insect scouting can occur at the same time diseases are being scouted. White grubs are the most common turf insect pests in Illinois. Be sure to check for them in late July in southern Illinois, early August in central Illinois and early to mid-August in northern Illinois. Scouting techniques are given in the discussion of the individual insects.
Scout for weeds beginning when the turf greens up in spring. Scouting includes evaluating the performance of previous herbicide applications and determines whether herbicides or other forms of control are needed. If winter annuals are prevalent in the spring, fall control methods should be contemplated. Late-summer scouting is done when mature weeds are easier to identify. Spring weed-control options can then be planned throughout the winter. A midsummer scouting may also be useful – especially for perennial broadleaf weeds – to evaluate fall control options.
In addition to the three major types of pests, scouts should look for abiotic problems such as chemical injury, nutrient deficiencies and environmental stress. Pests are not always the cause of abnormal symptoms exhibited by grass. For example, some herbicides can injure desired turf grass if not applied specifically as directed on the pesticide label.
Scouting for diseases, insects, weeds and abiotic problems, including drainage and other site problems, needs to be done repeatedly throughout the growing season as part of an integrated pest management program to become aware of changes that are occurring. This approach not only takes less time than searching for individual pests but also leads to a view of the turf system as a whole and to an observation of how various parts of the system interact.
Frequently, the answer to one maintenance or pest problem solves or causes another. A good integrated pest management program anticipates these reactions. For instance, poor drainage in a highly maintained turf area may promote the growth of nutsedge, as well as snow mold and black turf grass ataenius grubs. On the other hand, by looking at the problem overall, better drainage may solve all three conditions without the use of individual pesticides to control each problem.
Conversely, the answer to one pest problem may cause another. For example, the problem of thin, unhealthy turf on top of a berm is due to insufficient water and hot temperatures allowing weed encroachment and summer patch; it can perhaps be solved with additional irrigation. However, more watering can make the area more attractive to a white grub attack. Looking at and solving problems with the whole turf grass and pest situation in mind, you are accomplishing integrated pest management.
Scouting provides the tools with which to locate potential problems, but there are times when you may need additional help in identifying the cause. Also, some problems cannot be identified at the site and require a lab for positive diagnosis. The Plant Clinic at the University of Illinois in Urbana helps diagnose plant problems that are beyond the scout’s capabilities. When submitting a sample to the clinic, be sure to follow sampling procedures and fill out the proper paperwork. The clinic is open year round.
University of Illinois Plant Clinic
1102 S. Goodwin Ave.
S-417 Turner Hall
Urbana, IL 61802
Phone: (217) 333-0519
Maps or descriptions of disease, insect and weed pest location should be made for future reference. Rough maps of golf course tees, fairways and greens; commercial turf maps in relation to office buildings, roads, driveways, ponds and ornamental plantings, and home lawn maps can be useful. Maps with the house, garage, driveway, streets and trees illustrated make it easy to pinpoint turf pest locations in relation to those features. Written descriptions can be used instead of, or in addition to, maps to aid in locating potential pest sites in the future.
The maps or descriptions are valuable because pests tend to occur in the same sites year after year as long as the conditions causing them remain. Some of these conditions, such as poor drainage, soil compaction, extra irrigation, or susceptible turf cultivars may not be obvious but are important nonetheless. A large number of weeds can be an indication of turf management problems and/or environmental conditions.
Yearly maps also help identify expanding pest infestation areas. Nematode injury areas tend to increase slowly in square footage from year to year even though symptoms may be masked in cooler, wetter years. Billbug injury tends to increase from year to year or recur nearby when a treatment is made. Weed infestations may increase without treatment on a yearly basis and the maps help illustrate this increase.
The extent and heaviness of pest infestation should always be estimated. A heavy disease or weed infestation may require renovation, whereas lighter infestations may require only a change in cultural practices. Localized weed or insect infestations may only require spot treatment, instead of broadcast applications. Mapping helps clarify which control options should be considered.
Aesthetic injury is the measure of the visual and functional loss of the turf’s quality as a result of pest activity. The aesthetic injury level is the number of pests that cause enough damage to the appearance of a plant to warrant the cost of control. Turf is grown primarily for its aesthetic quality; that is, how nice it appears. A decrease in the pleasure that people obtain from looking at it, walking on it or conducting sports or other activity on it is considered aesthetic injury. Some forms of aesthetic injury are somewhat measurable, such as whether a golf ball skips on a fairway or whether a putt is knocked off course by a hole or weed. Loose turf due to white grub injury causing a fall is also easy to measure. A turf’s green color, its density or evenness, or the presence of various weeds is more difficult to measure; the perception of these characteristics varies from person to person.
Aesthetic injury also varies with damage location. The amount of turf damage on a golf course rough, fairway, or green is viewed differently, and corrective action requires different damage thresholds. Damage to a residential front yard or next to a heavily-used house entrance is not tolerated as much as the same amount of injury in the back corner of the yard. Additionally, less aesthetic injury may be accepted at the entrance to a commercial building than a remote area of a park. To be successful in damage evaluation, a scout has to develop an appreciation of the level of quality the owner desires in each location.
Robson, D., Wiesbrook, M., Voight, T., Nixon, P., Cleveland, T., & Gill, M. (n.d.). Turfgrass 39-1: Illinois Pesticide Safety Education Manual. Premier Print Group.
University of Illinois Pesticide Safety Education Program