Monitoring

Karen Delahaut, Outreach Specialist, UW-Madison

The cornerstone of any IPM program is regular monitoring. This isn’t the same as making a cursory observation of the plants when performing plant maintenance activities such as watering or repotting. It’s the regular, systematic inspection of selected crops. Regular monitoring and good record keeping skills are critical when diagnosing plant problems.

Some of the benefits of scouting or monitoring include damage prevention, or reduction, identification of the cause of the problem and the locations that require treatment, and identifying the most effective and economical method and timing of treatment. You should also monitor your crop after pest management actions have been taken to evaluate the effectiveness of the treatment. Most importantly, monitoring will allow for early detection of problems and will improve crop quality and sales revenue.

Monitoring can be as simple as a visual inspection of the crop or you can use sticky traps to monitor insect pests. Visual inspection is useful when monitoring exposed-feeding insects such as aphids, scales, or mealybugs. It can also be used to observe whether beneficial insects are present and at what level. Plant diseases are easily detected with visual observation as are problems associated with adverse environmental conditions and improper cultural practices.

Tools such as a maximum-minimum thermometer and yellow sticky traps are essential for monitoring environmental conditions and pest outbreaks. The color of the sticky trap is important. While yellow works for most insects, thrips actually prefer blue sticky traps and if you are growing crops in which thrips are a problem (chrysanthemums) you should have blue traps in the greenhouse. Humidity sensors are also suggested so you determine whether humidity levels are in the correct range for the crop grown. In sophisticated greenhouse ranges often the environmental monitoring equipment is connected to computerized systems that trigger the operation of heaters, ventilation fans, misters, and motorized shade screens.

To scout, begin by standing at the end of each pest management unit. This may be at the end of a particular bench for example. Look over the entire area and note any portions of the crop that look off-color, stunted, or otherwise unhealthy. In addition to examining crop plants, also look for other potential problems such as plant debris left on the greenhouse floor or weeds growing beneath the benches. Systematically examine plants at regular intervals along one side of the bench and then along the other side. Use colored flags to mark the location of problems so you can re-check these plants the next time you scout the crop.

Monitor insect pests such as mites that are easily dislodged, by shaking or tapping the plant over a clipboard with a white sheet of paper. Closely examine the paper and look for the number of live, dead, and parasitized insects. Identify the species of insect if possible.

Scouting once a week is adequate for most plants but plants for immediate sale, stock plants, high value plants, key plants, and plants with a history of pest problems should be scouted more frequently. Young seedlings or cuttings should be monitored at least every 3-4 days.

If you detect pest problems, you must decide whether action should be taken. To do so, you will need to determine your action threshold. In production agriculture, this is often referred to at the “economic injury level” – the level at which the amount of money lost because of a reduction of yield if nothing is done to manage the pest is greater than the cost of the treatment. This method isn’t always practical when assessing pest problems on plants that are being grown for their aesthetic appeal. In this case an “aesthetic injury level” is often used to determine when treatment is necessary. The difficulty with aesthetic injury levels is that they are subjective and don’t have a numerical value associated with them so some people tolerate more damage and higher pest levels than others. 

Finally, when scouting, not all plants require equal attention. Key plants are those species or cultivars that are most likely to be infested with a specific pest or disease. They may be susceptible because they aren’t adapted to the conditions in which they are being grown or they’re being grown under stress.  Some examples of key plants and their associated key pests are poinsettia and whiteflies, mums and thrips, and geraniums and Xanthamonas.

Be sure to keep complete and accurate records of your scouting observations so you have something to which to compare future observations.