The population of adult diamondback moths will be monitored from early-June through July. Monitoring is done using pheromone baited traps. Each week moths caught in the traps are counted, and data for that week, as well as cumulative moth counts, are entered into the table for the appropriate trapping area. The cumulative total number of moths will continue to rise until the end of the monitoring period.

The diamondback moth does not overwinter in North Dakota. Moths are carried into North Dakota from the southern U.S. on northerly winds in May or June. The traps will indicate if diamondback moth has arrived in an area.

The traps also indicate the risk of an infestation. The level of moths caught in the traps combined with weather conditions need to be considered when determining the risk of an infestation. A high level of diamondback moths in the traps early in the season has more of a potential for a damaging infestation than if high counts occur later in the season. For example, 100 moths caught in a trap during a week in June would indicate the potential for an outbreak exists. Factors such as parasites and weather conditions would determine to what degree the infestation develops. Rainfall is a natural control agent of diamondback moth, as it can easily dislodge young larvae from the plants and can drown larvae on the soil surface or in water trapped on the plants. Cool, cloudy weather reduces moth flight activity, and the longer inclement weather persists, the more females die before egg laying is completed.

A high risk of an infestation exists if high numbers of diamondback moth adults are found in the traps early in the season, and hot dry weather prevails from June to the harvesting of canola.