Assessing the Impact of Swede Midge on Canola Production in the

Prairies &

Dr. Rebecca H. Hallett, School of Environmental Science, University of Guelph Project Code: CARP 2005-14 Final Report: February 2008

Ecoclimatic modeling indicates that most of Canada is suitable for establishment of swede midge, including most of Saskatchewan. In 2007, swede midge were found in three fields in Saskatchewan for the first time. Although researchers expect the will become established and become a regular pest of canola in the Prairie provinces, they do not expect the populations to reach the high levels found in Ontario.

Ecoclimatic modeling indicates that most of Canada is suitable for establishment of swede midge, with high population growth possible in parts of British Columbia, Ontario, , New Brunswick, Nova Scotia, and Prince Edward Island. In Ontario, swede midge has now expanded to all of the areas considered favourable, and its range may still expand significantly. Most of Saskatchewan is ‘suitable’ for establishment of the swede midge and in 2007 the first populations were found in field surveys near Melfort and Yorkton.

The swede midge, nasturtii , is a gall midge native to Europe and Asia. The adult is a tiny, light-brown (1.5-2 mm), which is difficult to distinguish from many other closely related midge species. The first North American occurrence was found in Ontario in 2000 as a pest of plants in the family.

The goal of this three-year project launched in 2005, was to provide canola producers in the Prairie provinces and Ontario with information about the potential distribution and impact of the swede midge on canola production in order to help producers in affected and at-risk areas to adopt appropriate canola production and management practices. The project included the development of a climate model to determine the potential distribution of swede midge on the prairies, and field surveys of areas determined to be at risk. The project also investigated the susceptibility of spring canola varieties to swede midge and the impact of different seeding dates of both spring and winter canola. In the third year of the project, an additional field trial was conducted in Ontario to assess timing of insecticide sprays to protect vulnerable plant stages of spring canola.

Swede Midge surveys Using the ecoclimatic model developed, researchers quantified and mapped the areas across the Prairies that have ecoclimatic features conducive to swede midge population establishment and development. They also surveyed areas in the Prairie provinces determined to be at risk for the initial invasion of swede midge. Surveys were conducted at 9 locations across Alberta, Saskatchewan and Manitoba using pheromone traps in canola fields and cole crops. In August and September 2007 the first swede midge were found in three fields at Melfort, Yorkton and Nipawin. Fall soil cores were collected from the three canola fields that tested positive and three nearby fields, but no swede midge larvae were found. Researchers note that swede midge was also found in Nova Scotia for the first time in 2007 as well.

Varietal susceptibility The research results comparing susceptibility of spring canola varieties show that where swede midge is a concern, Brassica juncea and/or Sinapis alba varieties of canola should be selected over B. napus varieties, which are more susceptible to damage. At both Ontario research sites (Elora and Arkell) and for both primary and secondary racemes, damage was also significantly higher on untreated control plants than on those that received weekly foliar insecticide applications.

Damage at Vegetative Stage

D S A W M E A D G E E

M R I A D T G I E N G (0-3)

untreated foliar untreated foliar untreated foliar early early mid mid late late

Swede Midge & Canola Planting Date 2006 Spring Canola Trial, Elora, ON – at the vegetative state, swede midge damage was highest on late planted canola. Source: Rebecca H. Hallett, University of Guelph

Effect of planting date Researchers also compared planting dates of spring canola in replicated trials, planting early spring, two weeks after first planting and two weeks after second planting. The research results indicate that crop stage is an important factor in determining the susceptibility of canola to swede midge damage. In areas of swede midge infestation, canola must be planted early to avoid damage and late plantings should be avoided. By mid to late June, it may be best not to plant at all as damage will be very high, the crop will likely be unharvestable and resulting overwintering midge populations will present a risk to the following year’s crop. Researchers also recommend the production of winter canola over spring canola, as long as environmental conditions favour winter canola production.

Insecticide timing in spring canola Based on results from the first two years of the project indicating that late planted canola is particularly vulnerable to damage by swede midge, researchers conducted an experiment in 2007 at Elora and Arkell to compare insecticide treatments including: the control, the first bud stage, at branching and at first bud and branching stages. Although plants treated with insecticide at the bud stage at Elora had significantly less damage than other treatments, there were no significant differences found among treatments at Arkell on any dates.

PRIMARY RACEME (0 TO 4 scale)

D S A FLOWERING W M E A D G E E

M R I A D T G I E N G (0-4)

untreated foliar untreated foliar untreated foliar early early mid mid late late

Sweet Midge & Canola Planting Date 2006 spring canola trial, Elora, ON – at both the flowering and pod-filling stages, swede midge damage to both primary and secondary racemes was highest on late planted canola; particularly if not treated with insecticides. Source: Rebecca H. Hallett, University of Guelph

SECONDARY RACEME (0 TO 12 sc ale)

D S A FLOWERING W M E A D G E E

M R I A D T G I E N G (0-12)

untreated foliar untreated foliar untreated foliar early early mid mid late late

PRIMARY RACEME (0 TO 4 scale)

D A S M W FLOWERING A E G D E E

R M A I T D I G N E G

(0-4)

untreated foliar untreated foliar untreated foliar early early mid mid late late

SECONDARY RACEME (0 TO 12 scale)

D A S M W POD-FILLING A E G D E E

R M A I T D I G N E G

(0-4)

untreated foliar untreated foliar untreated foliar early early mid mid mid late

Scientific Publications

Olfert, O.O., Hallett, R.H., Weiss, R., Soroka, J.J. and S. Goodfellow. 2006. Potential distribution and relative abundance of swede midge, Contarinia nasturtii (Diptera: ), an invasive pest in Canada. Entomologia Experimentalis et Applicata, 120: 221-228.

Hallett, R.H., S.A. Goodfellow and J.D. Heal. 2007. Monitoring and detection of the swede midge (Diptera: Cecidomyiidae). The Canadian Entomologist, 139: 700- 712.

Mika, A.M., Weiss, R.M., Olfert, O., Hallett, R.H., and J.A. Newman. 2008. Will climate change be beneficial or detrimental to swede midge in North America? Contrasting predictions using climate projections from different general circulation models. Global Change Biology, 14: 1721-1733.

Hallett, R.H., Goodfellow, S.A., Weiss, R.M. and O. Olfert. 2009. MidgEmerge, a new predictive tool, indicates the presence of multiple emergence phenotypes of the overwintered generation of swede midge. Entomologia Experimentalis et Applicata, 130:81-97.

Hallett, R.H., M. Chen, M.K. Sears, and A.M. Shelton. 2009. Field efficacy of insecticides for control of the swede midge (Diptera: Cecidomyiidae) on cole crops. Journal of Economic Entomology, 102: 2241-2254.