By Carter Peru, PAg, Integrated Pest Management Specialist, Crops and Irrigation Branch, Regina
The 2025 growing season posed many challenges for farmers, including high insect pest pressure. Several insect surveys took place in 2025 with populations varying significantly depending on the insect species surveyed. Here, we highlight key findings from various insect monitoring programs conducted last year. Although fieldwork for insect surveys is complete, lab work for some surveys continues into winter, and results have yet to be finalized.
Diamondback Moth
Diamondback moth is a pest of concern in many brassicaceous crops, including canola and mustard. The survey uses pheromone traps to attract male moths. During the monitoring period, traps are examined weekly, and the number of moths caught is reported. Traps are placed early in the growing season to detect when populations arrive from the south (United States and Mexico).
In 2025, traps were placed in early May and monitored for 12 weeks. Results were reported weekly on Saskatchewan.ca and can still be viewed. Traps began catching diamond back moths in early May with numbers increasing until late July. Cumulative counts were low to moderate.
The population of diamondback moths in Saskatchewan relies on the arrival of adults on wind currents from the south since the moths do not overwinter in significant numbers in Saskatchewan. The early arrival of adults in Saskatchewan often leads to a more significant population buildup during the growing season. Although we monitor the arrival of adult male moths, it is the larval stage of this pest that causes crop loss, not the adult stage. Individual field scouting for the larval stage is necessary to determine if an insecticide application is warranted.
Bertha Armyworm
Like the diamondback moth survey, the bertha armyworm uses pheromone traps. Bertha armyworm larvae can feed on many crop species including canola, mustard and alfalfa. They overwinter as pupae below the soil surface and emerge as moths in spring. Traps were placed in canola crops during the growing season based on when pupal development was near completion (greater than or equal to 80 per cent pupal development) to help ensure traps are up when adults (moth stage) emerge. Emergence is highly dependent on temperature. In 2025, a majority of the pheromone traps were placed in mid-June and monitored until early August. Traps were placed throughout the canola-growing regions of the province. Counts were submitted weekly and used to create risk maps based on cumulative moth catches. These maps were released weekly during the monitoring season and are used to determine regional risk.
The average cumulative trap catches were much higher in 2025 compared to 2024. As depicted in the map, there were several hot spots of bertha armyworm moths detected, with cumulative catches exceeding 1,500 at some sites. Results from 2025 suggest populations are building in the province. Field monitoring in 2026 will be critical.
Monitoring male moths (adults) provides an indication of risk, but adults do not cause crop damage. It is critical to scout individual fields and apply economic thresholds based on larvae counts. Decisions to spray insecticide should never be based on regional risk maps.
Pea Leaf Weevil
The pea leaf weevil survey was conducted early in the growing season when field pea crops are in the second to sixth true leaf stage. Although faba bean fields are not assessed during the survey, they are a primary ‘true’ host in addition to field peas. This means these plants can support larval development. Adults will also feed on several other legumes. At each field, the surveyor examines plants for foliar notching damage caused by adult pea leaf weevils. These are characterized as “U” shaped notches. The number of notches per plant is averaged per field and used to generate the map. This map provides an indication of population levels in 2025 and an indication of regional risk for 2026.
The amount and range of notching damage observed during the 2025 survey was significantly higher compared to 2024. The 2025 map depicts significant notching damage in the east, central and northwest areas of the province. Although foliar notching damage assessment is a useful method to monitor this pest, notching damage itself usually does not cause significant yield loss. The larval stage of pea leaf weevil causes the most significant crop damage. Larvae feed on nitrogen-fixing nodules, reducing the amount of nitrogen the crop can fix. Registered insecticidal seed treatments are the most effective chemical control option for reducing loss due to this pest.
Grasshopper Survey
The grasshopper survey began in July and continued into September. Ditches were assessed for adult grasshopper densities. The targeted timing for this survey is when most grasshoppers are at the adult stage because the adults contribute to next year’s population. The survey is conducted by assessing sites once with a target of surveying four sites per rural municipality.
The 2025 map illustrates grasshopper densities based on the annual survey. The survey results show grasshopper populations greatly declined in 2025 compared to 2024. Much of the province had average grasshopper densities of less than two per meter squared. High grasshopper populations were observed in the west-central and south-central areas. It is important to scout for this pest in all areas of the province. The map is used for regional risk analysis only, not local infestations. High local populations may not be reflected in this map. Many factors, including environmental conditions, will dictate grasshopper populations in 2026.
Wheat Stem Sawfly
The 2025 wheat stem sawfly survey assessed fields for plants cut by sawfly larvae. Results show that sawfly cutting was down overall in 2025 compared to 2024. As depicted in the map, there was still significant cutting observed in the Regina area and areas in the southwest.
Spring and durum wheat are primary hosts of this pest, although several other grassy plant species can support the development of wheat stem sawfly. The larval stage of this pest causes crop damage as they feed on the pith of the plant causing significant reductions in yield and quality. Eventually, the larva will cut a groove completely around the inside of the stem which causes the stem to weaken and become susceptible to lodging. This results in plants lying on the ground, which cannot be harvested.
There are no registered pest control products for wheat stem sawfly control. Research has shown that chemical control is not an effective management method for this pest. The most effective management approach is to plant resistant cultivars or non-host crop species.
Cabbage Seedpod Weevil
The cabbage seedpod weevil survey is conducted when canola and brown/oriental mustard crops are flowering. Canola and brown/oriental mustard are the primary ‘true’ host crops although adults will feed on other plants. Yellow mustard is resistant to cabbage seedpod weevil.
During the survey, 25 sweeps are taken per field to catch adult weevils. The sweep samples are then assessed for the weevils and the total number caught per field is determined. The 2025 survey results indicate large populations in many parts of the province, including large areas that were not affected in 2024 or in previous years. Canola and mustard growers should be particularly vigilant with scouting in 2026 in areas where high populations were observed.
This map should be used for regional risk assessment. Individual fields must be scouted for adult weevils before deciding to apply insecticide. Both the larval and adult stages of cabbage seedpod weevil feed on host crops, with the larvae causing the most damage. The adults feed on flower buds and young flowers early in the season, and this feeding can contribute to ‘bud blast.’ Larvae develop inside pods and consume seeds, then chew their way out and fall to the soil to pupate. Adults that emerge in late summer can also feed on pods of late canola crops. Each larva consumes about five seeds during development. The infested pods are also susceptible to fungal infection as the feeding damage serves as an entry point for pathogens.
Additional Survey Information
Work associated with surveys continues throughout the winter months. Soil samples collected during the wheat midge survey are analyzed for the presence and abundance of wheat midge larval cocoons and levels of parasitism by the wheat midge natural enemy, Macroglenes penetrans. The viable (unparasitized) larval cocoon counts will be used to create the 2025 wheat midge map.