Soroka: Strategies for Managing Flea Beetle Populations in Canola

Date: May 2005
Term: 3 years
Status: Completed
Researcher(s): Juliana Soroka and Byron Irvine, Investigators, Agriculture and Agri-Food Canada, Saskatoon and Brandon Research Centres
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a

Project Summary

A three-year project conducted at Brandon and Saskatoon from 2002 to 2004 examined the effects of decreased proportions of seed treated with insecticide on control of flea beetle damage to canola seedlings. The results demonstrated that treating two of every three seeds with insecticides kept feeding by flea beetles at levels equivalent to that of all seeds treated. However, on an economic basis, there is currently no advantage to decreasing the level of insecticide treated canola seed, but other considerations may affect this assessment in the future.

A three-year project conducted at Brandon and Saskatoon from 2002 to 2004 studied methods to control flea beetles in canola while reducing insecticide levels in the process. The project examined the effects of decreased proportions of seed treated with insecticide on control of flea beetle damage to canola seedlings. The study also assessed seed yields of the various trials.

The study compared two reduced proportions of treated seed, consisting of 2/3 (0.67X) and 1/3 (0.33X) of the seed treated with insecticide, to all seeds treated (1X), and with fungicide alone (0X) and bare seed controls. The insecticide acetamiprid (Premium Plus®, Assail®) was evaluated at both locations from 2002 to 2004. The insecticide clothianidin (Prosper 200®) was evaluated in 2003 and 2004 at Brandon and Saskatoon. The insecticides were examined in separate trials, as the main purpose of the experiment was to examine differences among levels of treated seed, not differences between seed treatments. Three flea beetle damage ratings were conducted on all tissues at the cotyledon, 1st leaf and 2nd leaf stage to determine leaf area eaten and feeding level damage.

Decreasing treated seed ratios by one third had no consistent deleterious effects on flea beetle damage, seedling growth, plant density, seed yield, or net cash return. Flea beetle injury to seedlings in the 1X treatment was similar to that of seedlings in the 0.67X treatment, with only two exceptions, and it was almost always lower than that of seedlings without insecticide. The 0.33X treatment generally had flea beetle feeding levels between those of the two high and the two non-insecticide treatments. Plant stand and seedling growth rates with 1X and 0.67X treatments were similar and higher than with bare seed or fungicide-alone treatments. Seed yields were inversely proportional to flea beetle feeding levels. Under very heavy flea beetle feeding, seed yields and net cash returns were highest in 1X plots, but when flea beetle feeding pressure was less extreme and canola growing conditions were favourable, 0.67X seed yields and profits from them were comparable to those in 1X treatments. On an economic basis, currently there is no advantage to decreasing the level of insecticide treated canola seed, but other considerations may affect this assessment.

Source: AAFC

Researchers also conducted secondary investigations in five commercial canola fields, three in Manitoba and two in Alberta, to test the feasibility of border trap cropping, in which insecticides were placed with seed or foliarly-applied at the borders of fields only. They also conducted a trial with increased seeding rates around field perimeters to diffuse flea beetle feeding and minimize damage to individual seedlings. Although some interesting results were found, no definitive conclusions could be made from the investigations. However, the results suggest that these ideas should be investigated further.

Overall, the project demonstrated that treating two of every three seeds with insecticides kept flea beetles feeding at levels equivalent to that of all seeds treated. When feeding pressure was not extreme, seed yields were not compromised by the reduction in insecticide application. However, under extremely heavy flea beetle feeding pressures, additional insecticides need to be applied no matter what the initial application ratio.

Table 1. Average seed yields of canola cv SW Arrow at Brandon, MB, and Saskatoon, SK, from plots sown with five different ratios of acetamiprid or clothianidin-coated: uncoated seed, 2002-2004.

Acetamiprid Clothianidin

Seed ratio Brandon Saskatoon Brandon Saskatoon Brandon Saskatoon Brandon Saskatoon Brandon Saskatoon

Canola seed yield (kg ha-1)

1 Means within columns followed by the same letter are not significantly different, ANOVA at P≤0.05 and LSD; n.s. - not significant

2 From DeClerq, D.R. Reports on the Quality of Western Canadian Canola 2002, 2003, 2004, 2005. Canadian Grain Commission, Winnipeg. http://www.grainscanada.gc.ca/Quality/Canola/2003/canola-2003-e.pdf

Scientific Publications

Soroka, J. J., L. F. Grenkow, and R. B. Irvine. 2008. Impact of decreasing ratios of insecticide- treated seed on flea beetle (Coleoptera: Chrysomelidae, Phyllotreta spp.) feeding levels and canola seed yields. J. Econ. Entomol. 101 (6): 1811-1820.

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