Monitoring (Scouting)

insects on underside of leafOnce a pest manager has taken precautions to prevent pest infestations, it is important to watch regularly for the appearance of insects, weeds, diseases, and other pests. This is called monitoring.

The primary goals are to locate, identify, and rank the severity of pest infestations.  These data may also be used to project future populations through pest management models. In addition to giving solid data for making a management decision, regular monitoring works well for checking the success or failure of a control strategy. Pest populations vary from field to field, building to building, and year to year. Managing pests requires flexibility and an absolute commitment to pest monitoring. Pest monitoring is site-, crop-, and pest-specific. Each situation will require specialized knowledge and tools.

Monitoring pests involves:

man doing insect scoutingRegularchecking of a crop field, garden, greenhouse, golf course, warehouse, bakery, restaurant, field, greenhouse, golf course, or other areas and early detection of pests function together like an early warning system for pests, helping to prevent or minimize a pest outbreak.

Proper identification of pests is an extremely important prerequisite to handling problems effectively. For example, the brown banded and German cockroach can be easily confused with each other.  Identification is important because certain management practices may control only one species and not the other. Correct identification enables you to manage the real source of the problem and avoid merely treating the symptoms (or controlling organisms that are not pests).  Some pests cause similar damage.  Unless the pest is identified, the control program may have the wrong pest as its target.  Identification enables you to cure the pest problem and avoid injury to non-target organisms, particularly if you:

  • Japanese beetle eating a leafuse a pesticide that is specific to the pest;
  • control the pest effectively during the most susceptible stage of its life cycle;
  • consider the use of a non-chemical control.
  • Identifying the effects of naturally-present biological controlagents means knowing which organisms are beneficial and determining if pests have been affected by them.  Sometimes pests are kept in check naturally, and at other times the pest populations increase sharply.
  • Assessing the efficacy of pest management actions that have been taken is a very important part of monitoring. The scout must know the “what,” and “where” of the management actions taken and report successes or failures.

Monitoring tools and techniques:

The IPM Scout or technician is the most important part of a professional monitoring program. The scout works in a variety of situations, each requiring specific knowledge and tools.  However, diligent growers, golf course superintendents, homeowners, etc. can also monitor successfully for pests:


  • Flashlight
  • Black light (detect rodent urine)
  • Video camera
  • Screwdriver
  • Putty knife
  • Spatula
  • Tracking patches or powders]
  • Double-sided transparent tape (tree and shrub insects)
  • Shovel or spade

Monitoring pest populations with traps. The use of monitoring traps is highly recommended for certain insects, rodents and diseases.  Practically speaking, these devices are a must. They extend the eyes of the pest manager to places they cannot see and provide ongoing coverage.

Insect Monitoring Traps

Plastic bucket traps appear to be very efficient and economical.

Light traps are attractive to some insects, but pheromone traps offer increased flexibility in deployment and are much less expensive.

Sticky Traps: Some insects are attracted to bright yellow or other colors so they can be caught on colored sheets of plastic or cardboard that has been coated with glue. Sticky traps are usually used as a monitoring tool in greenhouses and orchards, although they can also be used as a control on indoor plants. By regularly checking the sticky traps a grower can find out when the first of the adult insects are present among the plants.

  • Yellow sticky traps attract adult whiteflies, flower thrips, fungus gnats, leafminers and cabbage loopers.
  • Bright blue traps are also available for flower thrips.

pheromone trapPheromone Traps: Individually packaged pheromone attractant traps are available for monitoring some species of moths. The traps are baited with a lure that mimics the odor given off by female moths to attract males for mating. The traps are used to find out when the main flights of adult moths occur so that sprays can be put on at the right time to have the greatest effect. Orchard growers use traps to time codling moth sprays so that they are used when the most moth eggs are hatching into caterpillars.

pitfall trapPlastic pitfall traps are used for crawling pests in the field as well as in stored grain bins. The species and number of insects found in a trap should be recorded and charts constructed so that changes in population size can be easily noticed.

Vertebrate Monitoring Traps Small secretive and sometimes nocturnal vertebrate pests are difficult to monitor. Traps are very important when checking on domestic rodent populations, mice and rats.

  • Snap trap (single catch),
  • Automatic trap (multiple catch),
  • Sticky trap (glue boards),
  • Single catch live box traps.

Digital monitoring tools:

Computers and other electronic tools are very much a part of IPM monitoring. Geographic Information Systems and Global Positioning Systems allow very precise mapping of areas. These devices, when used with soil mapping and yield monitors are part of a system called “Precision Agriculture”.

Precision agriculture has a lot to offer IPM, by identifying many crop yield- or quality-reducing factors using technology such as remote sensing and geo-referenced crop scouting (to measure crop vigor, quality and disease), yield monitors (to show yield variation), and crop and pest modeling. Precision applications of products to control pests are often more effective than conventional methods, and require less pesticide. Yield monitors and site-specific crop quality data provide a report card on how effective the crop production products and management tactics were. For example, a predicted disease level can then be used as the basis for a variable rate fungicide application and provide decision support for various production practices, such rootstock selection, fertilization, and irrigation.

Geographic Information Systems (GIS) are databases that store the relationship between data collected and their locations. Locations may be in real-earth coordinates Universal Transverse Mercator (UTM) coordinate system, longitude/latitude, or on a grid (i.e. X, Y coordinates). A GIS combines digital mapping, database functions, and spatial analysis.

Global Positioning Systems (GPS) is a U.S. space-based system that provides reliable positioning, navigation, and timing service worldwide.

An example of a practical IPM use of these devices is as follows.

  • The GPS system is used to map blacklight trap locations in agricultural areas used to monitor for crop pests. (The GPS units are accurate to within 10 feet.)
  • The trap counts are collected and entered into an Excel database which is linked to the GIS software.
  • The GIS software is used to create a map of the counts.
  • The maps are shared with growers in the community by sending a newsletter, fax, email or an internet web page.

Mapping the trap counts is useful for predicting where and when a pest will be arriving.  Additionally, the pest maps can be overlaid with weather maps that will help predict pest movement and the likelihood of damage to crops.

 GPS/GIS Mapping of Vegetable Insect Pests to Improve IPM

Pest Monitoring Links

Topics Included in this Module


Compiled by Ron Gardner

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