A big part of your pest control program
Clients often lack the ability to accurately determine which pests are responsible for a lawn problem, understand the importance of timing and how to interpret this information with respect to their part of the country. Teaching them about the importance of integrated pest management (IPM) and how thresholds play into the pest control program is a big part of your service to them.
Thresholds are a big part of IPM
All components of IPM must work together to efficiently and successfully control pests. Proper plant selection; disease and insect resistance; presence of endophytes; healthy soils that provide good rooting conditions; proper fertilization; thatch management; irrigation to meet the needs of the turf plant; and efficient mowing are all elements that fit together to create an effective pest management program for your customers.
One part that turfgrass managers often fail to consider are treatment or action thresholds, i.e., the number of pests needed to cause unacceptable damage to the turf. There are no exact numbers for thresholds, but when used conscientiously, they can help the turfgrass manager make better informed pest management decisions.
How are thresholds used?
Thresholds are estimates, not hard rules that apply to every situation. They are a number to start with, intended to be tweaked based on specific site and pest information.
As you consider the following factors, adjust them up or down to match each turf situation:
1. What’s unacceptable for one customer may not to another. Each shopping mall, residential lawn, campus grounds or city park is different in terms of how the owner/customer feels about the appearance of the turf. Some sites and customers call for nice green grass, but if a few weeds should pop up here and there or if one section is a little thin from time to time, they’re not going to be upset. In these locations, the number of pests that can be present before you undertake control measures can be adjusted upwards.
2. What’s unacceptable in the front yard may be OK in the side yard. For the entrance to a professional office complex, insurance building, bank or front yard in a gated community, the standard is a little higher. No doubt about it, certain parts of the landscape are more important than others. In high-visibility turf locations, there is a certain pride in ownership at stake; the way the property looks conveys a message from owner to friends or customers. Likewise, the way the property is perceived by others has an impact on the livelihood of a business or property value of a retail lot. In these locations, the numbers may need to be adjusted downwards.
3. In general, irrigated turf areas should be able to withstand more insect feeding than non-irrigated turf before the damage becomes visual. Because irrigated turfgrasses do not lack for water, their ability to re-grow after insect feeding injury is greater than those that might be water limited. In these locations, insect numbers can be adjusted upwards.
4. Each turfgrass species has a unique set of attributes that define its ability to perform during periods of drought, insect feeding or disease pressure. For example, tall fescue has a deep root system and can tolerate more white grub damage than shallow-rooted species such as Kentucky bluegrass. In locations where the turf species has significant adaptive or recuperative features, pest threshold numbers can be adjusted upwards.
Thresholds are flexible guidelines based on a series of key variables: pest species, abundance and life stage; species, cultivar, vigor and value of the turfgrass; relative effectiveness and cost of control measures; and time of year and environmental conditions. The best source of information on specific pest thresholds for your area is your state university or local extension office. The Internet can also provide valuable information on thresholds, but caution must be taken to ensure the accuracy of this information. When conducting a search, it is often best to seek out a university or educational Web site.
Misuse of thresholds
If you walk out on a property and see a browned-out area, get down on one knee and dig around in the grass for a few minutes with a pocketknife and find one or two armyworms, don’t claim this as a serious infestation—not only is this diagnosis inaccurate, it’s fraud. Almost certainly, the browned-out area is due to some abiotic problem such as excessive thatch, a fungal disease or perhaps even another insect pest. Instead, determine which causal agent is actually to blame for the brown spot, review the appropriate treatment options and/or corrective actions and then present these options to your customer.
Bottom line: If you see a few worms in the turf, don’t use this as an excuse to make an unnecessary insecticide application and charge the customer for an extra treatment. Consider the threshold.
John C. Fech is a horticulturist, certified arborist and frequent contributor located in Omaha, Neb. Frederick P. Baxendale is a professor and extension entomologist with the University of Nebraska-Lincoln.