2003 Canola Insect Trapping Network Final Report

2003 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 late June to mid-July. Highest trap catches were located at trap sites in Mountrail, Renville and Mercer Counties (Table 1). For example, North Ross and East Belden had a total of 654 and 445 moths per season, respectively. Other areas had cumulative trap catches below 300 and were at low risk of 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 3,607 with an average of 86 moths per trap day from 20 trap sites in 11 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 2003. Based on the Canadian trapping guidelines for infestation risk: - 17% (or 4 trap sites with 300-900 cumulative number of moths per trapping period) were in the “uncertain” risk level or unlikely that fields will be infested with larvae; and - 83% (or 19 trap sites with less than 300 cumulative number of moths per trapping period) were in the “low” risk of larval infestation. Overall, the cumulative number of bertha armyworms captured decreased in half from the cumulative numbers in 2002. The average moth per trap day was also about half as high as averages in 2002 (Table 2). Overall, bertha armyworm populations did not need to be controlled in the 2003 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 early in late May in the North Central Region of North Dakota. Trap catches of diamondback moth occurred in late April suggesting that some of the moths were able to overwinter in North Dakota last year. The second flight occurred mid to late June. There was a third and maybe a forth generation in July and August, respectively. The total number of diamondback moths captured was 8,802 moths with an average of 210 moths per trap day from 20 trap sites in 11 counties of North Dakota and 4 trap sites from northwest Minnesota (Table 3). These numbers are similar to last year 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 2003, diamondback moth arrived in low numbers early, but canola fields did not suffered any yield losses. Sites with the highest trap count of >500 moths per trap season included: Ward, Bottineau and Renville Counties of North Dakota, and Kennedy 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 “Pest Notes” during the 2003 field season: http://www.ag.ndsu.nodak.edu/minot/pest/pn.htm

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

Table 1. 2003 BERTHA ARMYWORM SUMMARY – sorted by trap site in descending order of total number for moths per trap season.

County	Site	Total # Moths	Total Trap Days	Moth/ Trapping Day	Moth/ Trapping Week
Mountrail	North Ross	654	41	16	112
Mountrail	East Belden	445	41	11	76
Renville	Mohall	442	56	8	55
Mercer	Hazen (1)	414	46	9	63
Bottineau	Kramer	275	46	6	42
Mountrail	North Belden	223	41	5	38
Bottineau	Bottineau	188	56	3	23
Mountrail	(Strobeck)	162	41	4	28
Bottineau	Gardena	146	46	3	22
Divide	Crosby	136	26	5	37
Mercer	Hazen (2)	132	46	3	20
Mountrail	North Stanley	102	41	2	17
Ward	Iota Flats	83	47	2	12
McKenzie	Arnegard	65	57	1	8
Ward	Minot	63	56	1	8
Cavalier	Langdon	45	37	1	9
Slope	Amidon	14	35	0	3
Minnesota	Roseau	6	42	0	1
Dunn	New Hradec	4	35	0	1
Minnesota	Kennedy	3	32	0	1
Minnesota	Grygla	3	42	0	0
Hettinger	New England	2	35	0	0
Minnesota	Thief River Falls	0	29	0	0

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

Year	-------------Bertha Armyworm-------------		-------------Diamondback moth-----------
Year	Total # Moths per trap season	Average moth per trap day	Total # Moths per trap season	Average moth per trap day
1998	2739	94	11348	195
1999	1939	39	5900	112
2000	1132	21	6515	123
2001	5003	87	17901	311
2002	6002	188	8174	195
2003	3607	86	8802	210

Table 3. 2003 DIAMONDBACK MOTH SUMMARY – sorted by trap site in descending order for total number of moths per trap season.

County	Site	Total # Moths	Total Trap Days	Moth/ Trapping Day	Moth/ Trapping Week
Bottineau	Kramer	1137	46	25	173
Bottineau	Bottineau	898	56	16	112
Minnesota	Kennedy	860	32	27	188
Bottineau	Gardena	831	46	18	126
Ward	Minot	754	56	13	94
Ward	Iota Flats	579	37	16	110
Renville	Mohall	560	56	10	70
Mercer	Hazen (2)	371	50	7	52
Hettinger	New England	219	35	6	44
Cavalier	Langdon	321	37	9	61
Minnesota	Roseau	319	42	8	53
McKenzie	Arnegard	280	57	5	34
Mercer	Hazen (1)	263	50	5	37
Divide	Crosby	208	26	8	56
Mountrail	North Ross	198	41	5	34
Minnesota	Grygla	161	42	4	27
Dunn	New Hradec	195	35	6	39
Mountrail	East Belden	135	41	3	23
Mountrail	North Stanley	117	41	3	20
Slope	Amidon	107	35	3	21
Mountrail	North Belden	100	41	2	17
Mountrail	Strobeck	100	41	2	17
Minnesota	Thief River Falls	89	22	4	28

*Diamondback moth Summary*				*Numbers*
Total number of Moths				8802
Average Trap Day				42
Average Moth per Trap Day				210

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.