Purpose and Objective: 

To monitor for three insect pests of canola using pheromone traps and sticky traps in the major canola growing areas of North Dakota: Bertha armyworm (Mamestra configurata), Diamondback moth (Plutella xylostella), and crucifer flea beetle (Phyllotreta cruciferae). Trap data provided  growers, Ag consultants, Ag field researchers, and extension agents/specialists with an  "early" warning system of when the pest were active and how many. 

Summary of Results 

Bertha Armyworm: 
The peak flight for Bertha armyworms (BA) occurred during late June to early July. Highest trap catches were located at trap sites in Bottineau  County (Table 1). East Mohall and Westhope had a total of 927 and 871  moths per season, respectively. Other areas had cumulative trap catches  below 300 and were at low risk of infestation. No bertha armyworm was  captured at Mercer, Hazen County. The cumulative moth capture during  2002 was 6,002 with an average of 188 moths per trap day from 32 trap sites including 13 counties in North Dakota and 2 counties in Minnesota. In Table 2, the cumulative trap capture and the average number of moth per trap day are listed from 1998 through 2002. 

Overall, the total number of bertha armyworm captured was similar to numbers in 2001 with the  peak flight occurring between late June and mid-July. However, the average moth per trap day  was twice as high as 2001 (Table 2). Since the canola crop was also planted later in 2002, the  larvae primarily fed on the leaves and not the pods causing minimal impact to canola yields.  However, there was limited spraying in isolated "hot" spots. The presence of natural controls like a nuclear polyhedrosis virus and fungi were common in fields as well. Bertha armyworm populations will need to be monitored until local populations decrease in the areas with high pheromone trap catches.

Crucifer Flea Beetles:

During 2002, the crucifer flea beetle (FB) activity started late, close to late-May, which was similar to 2001. A total of 35,597 FBs were captured on sticky yellow traps from 17 different trap sites with an average trap catch of 818 beetles per trap day (Table 4). The highest average trap catch  was 187 beetles per trap day in Minot, 164 beetles per trap day in Souris, and 102 beetles per trap day in Langdon. There were two major peaks with the major activity in late May, and again in late June. Minot had the highest cumulative trap catch with 18,504 total FBs, then Souris with 7,034  total FBs, Langdon with 3,993 total FBs. The FB trap catches were lower at other sites partly  because the monitoring effort was not as continuous throughout the field season, and traps may  have been placed in commercial insecticide seed-treated canola fields. Traps were also monitored longer (end of July) at the research extension centers. Flea beetle pressure was generally lower from regions where canola has been grown for only a few years, such as Southwest. The duration of the feeding period was typical – approximately 1 to 1.5 months long. The majority of the canola crop was planted during mid to late May in the North Dakota, which provided opportune time for the emerging flea beetles to infest. The weather conditions in 2002 were conducive to early flea beetle feeding throughout North Dakota. As a result, most canola fields were severely damaged from FBs. Many fields had to be rescued with one or more applications of a foliar insecticide regardless of whether the seed was treated with an insecticide or not.

Canola Insect Trapping Network Web Site: 

Data for the Canola Insect Trapping Network was updated weekly on the NC Research Extension Center’s webpage under "Pest Notes" during the 2002 field season:

                                                http://www.ag.ndsu.nodak.edu/minot/pest/pn.htm 

Please see the website for more information from the different field sites. 

Acknowledgments: Authors would like to thank the numerous trap cooperators, which included County Extension  Agents, Area Extension Specialists, Crop Consultants in North Dakota and Minnesota for making this a successful network.

Table 3.  2002 DIAMONDBACK MOTH summary–sorted by trap site in descending order for total number of moths per trap season.

Table 4.  2002 FLEA BEETLE SUMMARY–sorted by trap site in descending order for total number of beetles per trap season.