Soroka: Mitigation of Risk to Canola from Spring Flea Beetle Injury
Date: April 2013
Term: 4 years
Status: Completed
Researcher(s): Juliana Soroka, Robert Elliott, Owen Olfert, Chrystel Olivier, Russell Hynes, Agriculture and Agri-Food Canada, Saskatoon; Jennifer Otani, Agriculture and Agri-Food Canada, Beaverlodge, AB; Lloyd Dosdall and James Tansey, University of Alberta, Edmonton, AB; John Gavloski, Manitoba Agriculture, Food and Rural Development, Carman, MB
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
A four-year study initiated in 2010 was conducted in western Canada to investigate the differences in biology of two flea beetle species, Phyllotreta striolata (striped) and P. cruciferae (crucifer), in order to better target management methods. The results of the study showed that crucifer and striped flea beetles react differently to their environment, each preferring slightly different optimum climate factors, and having slightly different spring emergence and dispersal characteristics. The differences between the species was especially noticeable in their response to neonicotinoid seed dressings, with striped flea beetles being less susceptible to control by the insecticides tested. This highlights the importance of producer monitoring of newly emerging canola fields for evidence of flea beetle damage to canola seedlings.
Flea beetles are the most important chronic insect pest of canola on the Canadian prairies, with annual yield losses to the crop from flea beetle damage often exceeding $300 million. Researchers are finding evidence of a shift in distribution of the two principal crucifer-feeding flea beetle species in the southern areas of prairie canola production, which may have biological differences that affect their potential impact on the crop.
Researchers with Agriculture and Agri-Food Canada (AAFC) in Saskatoon, Saskatchewan led a four-year study starting in 2010 to investigate the differences in biology of two flea beetle species, Phyllotreta striolata (striped) and P. cruciferae (crucifer), in order to better target management methods. A bioclimatic model of the two species is being developed to determine species distributions and abundance.
The objectives of the study were to quantify the risk of injury by flea beetles to prairie canola production by determining the factors that affect distribution, spring emergence, flight, and feeding levels of the two principal crucifer-feeding flea beetle species. Researchers also wanted to investigate conditions and reasons for seed treatment failures as well as alternatives to seed treatments for flea beetle control.
The study was conducted in four geographic locations in western Canada: Carman, Manitoba, Saskatoon, Saskatchewan, and Edmonton and Beaverlodge, Alberta. To better understand the differences in the biology of the two flea beetle species and their potential impact on canola production, the study included bioclimate modelling, field trap and crop trials, laboratory and growth chamber studies. Both growth chamber experiments and field trials were conducted to investigate reasons for seed treatment failures.
The results of the study showed that crucifer and striped flea beetles react differently to their environment, each preferring slightly different optimum climate factors, and having different spring emergence and dispersal characteristics. P. cruciferae is most abundant in the southern Canadian prairie regions, and P. striolata has traditionally been found in greatest numbers along the northern Parkland of the prairies and in the Peace River Region of Alberta. It is probable that if changes in distribution of the two species are occurring, the cause is not directly related to climate, or at least, not climate alone.
From tower trap data collected in commercial fields, researchers found that flea beetle flight height is dependent principally upon ambient temperatures, relative humidity, and wind speed. Flight occurs throughout the growing season, and flights can be longer and more sustained than previously thought. Beetle flight height increased with mean and minimum ambient temperatures for both generations of beetles, with 15˚C determined as an estimated minimum temperature for flight. Crucifer flea beetles prefer to fly in some, but not excessive, wind, with flight activity greatest at wind speeds of approximately 10 km per hour. The study also found that canola mustard is more susceptible to striped flea beetle damage at higher temperatures than open pollinated and hybrid canola.
Laboratory trials were conducted to test inoculation of canola with Burkholderia phytofirmans and determine its effects on flea beetle feeding. B. phytofirmans is a plant-associated bacterium with beneficial plant properties. As a seed dressing, the bacterium did not reduce flea beetle feeding damage but did improve germination at 5°C compared to untreated seed.
The difference between the species was especially noticeable in their response to neonicotinoid seed dressings, with striped flea beetles being less susceptible to control by the insecticides tested. The study showed that neonicotinoid seed treatments provided substantially better control and protection against crucifer flea beetles than striped flea beetles. Therefore, seed treatment failures are more likely to occur when striped flea beetles are the most abundant species in commercial fields.
Neonicotinoid seed treatments also provided better flea beetle control in dry soil (20-30% moisture content) than in wet soil (60-90% moisture content). Therefore, seed treatment failures are more likely to occur when above-average rainfall causes saturated soil conditions during germination and seedling emergence. In check treatments, higher temperatures resulted in a rapid increase in feeding damage from crucifer and striped flea beetles. Mortality of crucifer flea beetles from neonicotinoid seed treatments also increased rapidly (20-60%) between 10°C and 30°C. Consequently, damage was below the economic threshold (25% damage) in all treatments in dry and wet soil at 10, 20 and 30°C.
In contrast, mortality of striped flea beetles from neonicotinoid seed treatments in dry and wet soil increased by 0-35% between 10°C and 30°C. As a result, feeding damage exceeded 25% in some treatments in dry soil at 30°C and exceeded 25% in most treatments in wet soil at 30°C. Therefore, seed treatment failures against striped flea beetles are most likely when saturated soil and high temperatures occur during germination and seedling emergence.
The research points out the lack of efficacy of neonicotinoid seed dressings in control of striped flea beetles under certain growing conditions. This highlights the importance of producer monitoring of newly emerging canola fields for evidence of flea beetle damage to canola seedlings.
Scientific Publications
Tansey, J.A., Dosdall, L.M., Soroka, J.J., and Keddie, A. 2014. The influence of weather on crucifer flea beetle capture heights. The Canadian Entomologist. In press.
Full Report PDF: n/a