NDSU

2004 Canola Insect Pest Trapping Network

Janet J. Knodel, Area Extension Specialist - Crop Protection

Lorilie Atkinson, Research Specialist

North Central Research and Extension Center, Minot, ND

Objective:

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

Results and Discussion

Bertha Armyworm:

            The peak flight for Bertha armyworms occurred during mid-July, one to two weeks later than 2003.  Highest trap catches were located at trap sites in the northern tier of North Dakota – Cavalier, Burke, and Botineau Counties (Table 1).  For example, Langdon and Bowbells had a total of 100 and 85 moths per season, respectively.  All trap sites had cumulative trap catches below 300 and were at “low” risk of larval infestation.  Sites with no or few bertha armyworms included all of the Minnesota and southwestern North Dakota trap sites.  The cumulative number of moths during 2003 was only 573 with an average of 16 moths per trap day from 14 trap sites in 10 counties in North Dakota and 4 sites in northwestern Minnesota. 

            In Table 2, the cumulative number of moths per trap season and the average number of moths per trap day are listed from 1998 through 2004.  Overall, the 2004 trapping season shows a dramatic decrease in cumulative trap catches from previous years.  The average moth per trap day was also about 80% lower than the averages in 2003 (Table 2).  In summary, the bertha armyworm population did not need to be controlled in the 2004 canola crop.  It appears that local populations are decreasing in the areas with past histories of high pheromone trap catches.  Monitoring efforts should be continued to track any potential increases in Bertha armyworm populations.

Diamondback Moths:

            Diamondback moth migrated into North Dakota in mid to late May.  The first flight of diamondback moths was later than normal about mid-late June in the North Central Region of North Dakota.  The second flight occurred mid to late July.  There was probably a third generation in late August.  The total number of diamondback moths captured was 7,183 moths with an average of 131 moths per trap day from 14 trap sites in 10 counties of North Dakota and 4 trap sites from northwest Minnesota (Table 3).  These numbers are slightly lower than last year’s trap counts (Table 2).  Field scouting is usually necessary when more than 100 diamondback moths are captured per trap week for several weeks prior to bloom to early bud development.  In 2004, diamondback moth arrived in low numbers late, and canola fields did not suffered any yield losses due to injury.  Sites with the highest trap count of >500 moths per trap season included: Ward, Slope, Stark, and McKenzie Counties of North Dakota, and all four trap sites in Minnesota.

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 “Insect Trap Monitoring and Insecticide Projects” during the 2004 field season:

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

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

Table 1.   2004 BERTHA ARMYWORM SUMMARY – sorted by trap site in descending order of total number for moths per trap season.

Table 2.  Pheromone Trap Catches for Bertha Armyworm and Diamondback moth - 1998 to 2003.

Table 2.  2004 DIAMONDBACK MOTH SUMMARY – sorted by trap site in descending order for total number of moths per trap season.

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.