Elliott: Effect of neonicotinoid seed treatments on flea beetle damage and performance of Polish canola (Brassica rapa) in 2003-2005
Date: May 2007
Term: 3 years
Status: Completed
Researcher(s): Bob Elliott, Larry Mann and Owen Olfert, Agriculture and Agri-Food Canada, Saskatoon
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: MCGA, Canola Council of Canada, Syngenta
Project Summary
The objectives of this study were to determine the effect of neonicotinoid seed treatments on flea beetle damage and the performance of Polish canola. Seed treatments reduced flea beetle damage and improved the performance of open-pollinated and synthetic Polish canola in all tests. Treatments that provided the longest flea beetle protection usually provided the best seedling establishment, highest plant weight and highest yield. Prosper®, Helix® and Helix XTra® were the only neonicotinoid seed treatments that improved yield significantly when flea beetle damage was above or below the economic threshold.
The crucifer flea beetle, Phyllotreta cruciferae, is a serious pest of Polish canola (Brassica rapa) in western Canada. After overwintering in canola stubble and non-crop areas, adult beetles migrate into canola fields and feed on emerging seedlings. Feeding injury to the cotyledons, true leaves and stems results in seedling mortality, reduced seedling growth, delayed maturity, reduced grade and lower seed yield. Cultural practices and biological agents provide limited regulation of flea beetle populations, so canola producers are reliant on seed treatments and foliar-applied insecticides. An insecticidal spray is recommended when flea beetles damage more than 25% of the cotyledon or leaf surface.
The objectives of this study were to determine the effect of neonicotinoid seed treatments on flea beetle damage and the performance of Polish canola. Varieties of open-pollinated and synthetic B. rapa mature within 86-92 days and are typically seeded in late May or early June when flea beetle populations tend to decline.
Field experiments were conducted in 2003-2005 on certified seed lots of a conventional open-pollinated variety and synthetic variety of B. rapa, including ‘AC Parkland’ and ‘Hysyn 110' in 2003 and ‘AC Sunshine’ and ‘ACS-C7' in 2004 and 2005. The treatments included untreated seed, Foundation Lite® (fungicides only), Assail 50 SF® (400 g acetamiprid/100 kg seed), Gaucho CS FL® (400 g imidacloprid/100 kg seed), Prosper® (200 g and 400 g clothianidin/100 kg seed), Helix® (200 g thiamethoxam/100 kg seed) and Helix XTra® (400 g thiamethoxam/100 kg seed). Experiments focused on the effect of the treatments on flea beetle damage to the cotyledons, seedling emergence, stand establishment, shoot growth, biomass accumulation and seed yield. Shoot biomass was calculated from the number of seedlings/m-row and shoot weight.
Yearly comparisons
The effects of seed treatments on flea beetle damage and performance varied yearly but were consistent in the two varieties from year to year. Damage to seedlings grown from untreated seed after 21 days was higher in 2003 (27-30% damage) than in 2004 (19-20% damage) and 2005 (11-15% damage). Damage, seedlings/row, shoot dry weight and shoot biomass were not significantly different in the open-pollinated variety and synthetic variety on most sampling dates. Seed yields over 3 years were 5% higher in the synthetic variety (27.9 bu/acre) than in the open-pollinated variety (26.6 bu/acre).
Flea beetle damage
Seed treatments had a significant effect on flea beetle damage to the cotyledons 14, 18 and 21 days after seeding. In each test, damage was highest in seedlings grown from untreated seed and seed treated with Foundation Lite® or Assail®. Gaucho® provided an intermediate level of protection. In ascending order, Prosper® (200 g rate), Helix®, Prosper® (400 g rate) and Helix XTra® provided the best flea beetle protection. Compared to untreated seed, treatments reduced damage over 3 years by 7-12% after 14-18 days and by 6-8% after 21 days.
Emergence and establishment
Seedling emergence after 14 days varied depending on the year and seed treatment. Foundation Lite® had little or no effect on emergence of the two varieties. Neonicotinoid seed treatments improved emergence in 2003 when flea beetle damage in untreated check plots averaged 27-30%. However, treatments did not promote faster emergence in 2004 and 2005 when flea beetle damage averaged 11-20% in the check plots.
The effect of seed treatments on establishment varied from year to year. Establishment of untreated seed after 28 days averaged 56-61% in 2003, 68% in 2004 and 83-85% in 2005. Foundation Lite® had no effect on stand establishment. Compared to untreated seed, Assail® improved establishment of the two varieties by 4-5% in 2003 and by 4% or less in 2004 and 2005. Stand establishment was higher with other neonicotinoid seed treatments. Results indicated that Gaucho®, Prosper®200, Prosper®400, Helix® and Helix XTra® improved stand establishment when flea beetle damage exceeded 25% damage in 2003. However, the treatments did not promote higher plant stands when damage averaged 15% or less in 2005.
Shoot growth
Seed treatments had a significant effect on shoot growth of open-pollinated and synthetic Polish canola. In most tests, untreated seed and seed treated with Foundation Lite®, Assail® or Gaucho® had the lowest shoot dry weight after 21, 28 and 35 days. Seeds treated with Prosper®200, Prosper®400, Helix® or Helix XTra® had the highest shoot weights on most sampling dates. Improvements in shoot weight in 2004 and 2005 suggest that low or high rates of Prosper® and Helix® promote shoot growth when flea beetle damage is less than 25%, the economic threshold. Of the treatments tested, Helix XTra® had the greatest positive effect on shoot growth when flea beetle damage was above or below the economic threshold.
Biomass accumulation
Seed treatments had a significant effect on the shoot biomass of open-pollinated and synthetic Polish canola after 21, 28 and 35 days. In most instances, untreated seed and seeds treated with Foundation Lite® or Assail® had the lowest shoot biomass. Improvements in shoot biomass in 2004 and 2005 indicate that Helix®, 400 g rate of Prosper®, and Helix® XTra enhance biomass accumulation when flea beetle damage is below the economic threshold. Of the treatments tested, Helix XTra® had the greatest positive effect on biomass accumulation when flea beetle damage was above or below the economic threshold.
Seed yield
Seed treatments had a significant effect on the yield of open-pollinated and synthetic Polish canola. In each year of testing, yield of untreated seed was not significantly different from that of seeds treated with Foundation Lite®, Assail® or Gaucho®. However, yields of the two cultivars over 3 years improved by 11% with Helix®, by 12% with the 400 g rate of Prosper®, and by 17% with Helix XTra®. Compared to untreated seed, economic returns increased by $20.30/acre ($50.14/ha) with Helix®, by $21.70/acre ($53.60/ha) with the 400 g rate of Prosper®, and by $28.00/acre ($69.16/ha) Helix XTra®.
For information on related studies, go to:
Elliott.CARP2004-14.2. Effect of neonicotinoid seed treatments on flea beetle damage and performance of Argentine canola (Brassica napus) in 2003-2006
Elliott.CARP2004-14.3. Effect of seeding date and seeding rate on flea beetle damage and agronomic performance of open-pollinated and hybrid Argentine canola under different tillage practices in 2001-2006
Elliott.CARP2004-14.4. Effect of seeding rate on flea beetle damage and agronomic performance of sized seeds of open-pollinated and hybrid Argentine canola in 2004-2006
Elliott.CARP2004-14.5. Effect of seed quality on the performance of hybrid Argentine canola in early- and late-seeded plots with conventional and minimum tillage
Elliott.CARP2004-14.6. Effect of production practices and seed quality on the performance of open-pollinated Argentine canola in conventional, minimum and zero tillage