Soroka: Potential Flea Beetle Species Composition Shift in Prairie Canola
Date: March 2012
Term: 5 years
Status: Completed
Researcher(s): Juliana Soroka, Agriculture and Agri-Food Canada (AAFC), Saskatoon Research Centre, SK
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: ACPC, MCGA
Project Summary
Crucifer-feeding flea beetles, principally Phyllotreta cruciferae (crucifer flea beetle) and P. striolata (striped flea beetle) are the most economically damaging insect pests of canola on the Canadian prairies. The primary means of flea beetle management in canola is the use of insecticidal seed treatments, most of which were developed and tested against P. cruciferae. Laboratory tests have shown that the neonicotinoid insecticides that replaced lindane seed treatments may not be as effective in controlling P. striolata as they are against P. cruciferae, and there have been reports of increasing numbers of P. striolata. Researchers at AAFC in Saskatoon conducted a five-year study to determine the numbers and distribution of the flea beetle species most commonly found in prairie canola fields. The results show that P. cruciferae still remains the predominant flea beetle in fields with high numbers of flea beetles, although the survey found that P. striolata is expanding its range of occurrence across the prairies.
Crucifer-feeding flea beetles, principally Phyllotreta cruciferae and P. striolata are the most economically damaging insect pests of canola on the Canadian prairies. The crucifer flea beetle (P. cruciferae) is most frequently found in the southern Canadian prairie regions, while the striped flea beetle (P. striolata) was traditionally found along the Parkland region of the northern prairies and in the Peace River Region of Alberta. A third species, the hop flea beetle (Psylliodes punctulata) occurs on low numbers across the prairies, while several other flea beetle species found in prairie canola are of minor importance.
The primary means of flea beetle management in canola is insecticidal seed treatments, most of which were developed and tested against P. cruciferae. Laboratory tests have shown that the neonicotinoid insecticides that have replaced lindane seed treatments may not be as effective in controlling P. striolata as they are against P. cruciferae. As well, there have been reports that populations of P. striolata are increasing in numbers and range.
Researchers at AAFC in Saskatoon conducted a five-year study across the prairies to determine the numbers and distribution of the flea beetle species most commonly found in prairie canola fields. They also wanted to determine if striped flea beetle numbers were increasing over historical levels, indicating a major shift in flea beetle species in Canadian canola fields.
In 2007, a preliminary survey was conducted at 25 locations across the Canadian prairies. The survey was expanded in 2008 to include 34 sites, in 2009 to survey 44 sites, in 2010 to survey 98 sites, and in 2011 to include 99 sites across the Canadian prairies and North Dakota. Flea beetles were monitored using series of 13.0 x 7.5cm yellow sticky traps placed in or near canola fields and changed regularly for periods ranging from one week in spring to the entire summer, but averaging three to four weeks in May-June, starting at the time of canola emergence. Traps were examined and the number and species of flea beetles on the traps were identified.
Figure 1. Proportion of flea beetle species collected form yellow sticky traps placed near or in canola fields in the spring across the Prairies, 2001-2011.
Although local exceptions occurred, in general spring weather conditions in the years of the survey were not conducive to the development of high flea beetle populations, especially in 2010 and 2011, when cold and wet conditions predominated over much of the northern Grain Belt and most populations of flea beetles were very low. The Peace River area of northern Alberta was the only region that was consistently dry in the spring during the years of the survey. Except for sporadic, isolated foliar spraying for flea beetle control elsewhere, the Peace River region was the only region that required widespread foliar application over multiple years. The number of flea beetles caught on traps in the survey reflected the inclement spring weather conditions.
In total, over the five years 11,180 traps were retrieved from 300 sites and examined for flea beetle species and numbers. Although there were some site specific and location variations, generally flea beetle species distribution tended to follow traditional patterns. P. striolata was common in northern areas of Canada, and P. cruciferae was the main beetle captured near the 49th parallel. However, compared to results from surveys conducted in the 1970s, the magnitude of P.striolata numbers in northern areas has increased dramatically, and P. striolata has displaced P. cruciferae as the most frequently encountered flea beetle in central Alberta, central Saskatchewan, and much of Manitoba. And once rarely encountered in the rape/canola fields of southern Canada, P. striolata is now found there in increasing numbers. Several species of the genus Chaetocnema, a flea beetle not recognized as a pest of Canadian canola, were found in increasing locations and numbers in the survey.
Although the survey found an increasing occurrence of P. striolata and other flea beetle species across the prairies, overall P. cruciferae remained the predominant flea beetle in fields with the highest numbers of flea beetles. Most sites with high flea beetle numbers were located in the southern Canadian prairies, and in such locations P. striolata may have less optimum levels of developmental parameters than P. cruciferae. Investigations on interactions between the two species could answer some of the questions surrounding flea beetle species development in prairie canola fields.
Figure 2. Flea beetle species with the greatest cumulative number of beetles caught from the beginning of sampling in spring until the first week of July in 2007, 2008 and 2011.
Full Report PDF: Potential Flea Beetle Species Composition Shift in Prairie Canola