By Carter Peru AAg, Integrated Pest Management Agrologist, Regina
The 2018 field surveying season is now complete. The information gained from field surveying is used for a variety of purposes, including the creation of forecast maps and producing disease situation reports. How the information is used is dependent on the particular survey.
Pea Leaf Weevil Survey
The pea leaf weevil (PLW) survey results show that PLW damage across the province this year was very low, with the exception of a couple of areas in the south-west corner of the province, which had slightly higher observed foliar notching damage. The low amount of notching damage observed this year could be due to environmental factors such as harsh overwintering conditions and/or an increase in the use of seed treatments that control PLW. For the PLW survey, the foliage of pea plants is evaluated for the distinctive notching that is caused by the feeding of adult PLW. Although the main damage of concern is caused by the larval stage of PLW feeding on the nodules of plants, the above-ground notching provides a good indication of the PLW population. Monitoring the adult PLW population and distribution in the 2018 season provides an indication of what population levels may be like for the 2019 growing season. The 2018 PLW survey map is shown in image 1.
The grasshopper density counts overall were light to very light. For this survey, adult grasshoppers are counted for a particular distance in order to calculate the density of grasshoppers present. The grasshoppers survey results are used to generate a forecast map for the 2019 growing season. The survey map displaying the 2019 grasshopper forecast is now available.
Bertha Armyworm Survey
The bertha armyworm (BAW) survey was completed earlier in the season. This is a pheromone trap-based survey and relies on weekly counts from cooperators around the province. A total of 238 sites were monitored for BAW in 2018. The pheromone traps catch BAW moths, the adult stage of BAW. Although the adults are caught, it is the larval stage that causes crop damage and that should be scouted for before making a decision to spray an insecticide. BAW populations were higher in 2018 than they were in 2017. Large numbers of moths were caught in the Outlook and Watrous areas. Maps are released weekly from April until early August, displaying the cumulative moth counts.
Diamondback Moth Survey
The diamondback moth (DBM) survey is also a pheromone trap-based survey that takes place from April until June. DBM counts were low throughout the province. A total of 45 sites were monitored for DBM in 2018. Like the BAW survey, the pheromone traps catch the adult moth stage of DBM. The larval stage of DBM is the stage that causes crop damage (image 2).
Several plant disease surveys also took place this year, including the lentil and canola disease surveys. Watch for a future SaskAg Now article that will discuss the results of the 2018 plant disease surveys.
Once the 2018 disease survey results have been reviewed and finalized, the disease situation will be posted on the Canadian Phytopathological Society website. Crop disease situation reports from previous years can also be viewed on this website.