R.M. Weiss

Potential distribution and relative abundance of swede midge, Contarinia nasturtii, an invasive pest in Canada

The swede midge, Contarinia nasturtii (Kieffer) (Diptera: Cecidomyiidae), is a pest of most cultivated Brassicaceae such as broccoli, canola, cauliflower, cabbage, and Brussels sprouts. The species primarily has a Palaearctic distribution and occurs throughout Europe and southwestern Asia to the Caucasus. Between 1996 and 1999, producers of cruciferous vegetables in Ontario, Canada, reported crop damage that was consistent with damage symptoms characteristic of C. nasturtii feeding and in 2000, field studies confirmed that this damage was caused by C. nasturtii. A bioclimatic model was developed to predict potential range and relative abundance of C. nasturtii in Canada in order to determine the impact of the establishment and spread of C. nasturtii populations. Model output indicated that C. nasturtii could potentially become established in all provinces of Canada, with the risk being greatest in southwestern British Columbia, southern Ontario and Quebec, New Brunswick, Nova Scotia, and Prince Edward Island. Results indicated that C. nasturtii population growth in the Prairie Ecozone of western Canada would be greatest in years with above average precipitation.

MidgEmerge, a new predictive tool, indicates the presence of multiple emergence phenotypes of the overwintered generation of swede midge

The swede midge, Contarinia nasturtii (Kieffer) (Diptera: Cecidomyiidae), is a pest of cruciferous crops (Brassicaceae) in Europe and North America with high potential for economic impact. Effective timing of insecticide applications for swede midge control is difficult, in part due to a short adult lifespan. Predictive models are often used in integrated pest management programmes to facilitate the timing of control strategies. A European model, Contapré, for predicting adult swede midge emergence was shown to be inaccurate under Ontario field conditions. A new predictive model, MidgEmerge, was developed using DYMEX™ modelling software. MidgEmerge accurately predicts swede midge emergence in both Ontario and Québec. Observed emergence patterns cannot be explained without the presence of multiple emergence phenotypes. MidgEmerge indicates that there are two emergence phenotypes of the swede midge, each completing four generations per year in southern Ontario. A fifth generation of each may become possible with climate change. Evidence of a possible third emergence phenotype is presented. MidgEmerge has the potential to be an important predictive tool to inform and direct integrated pest management practices targeted against swede midge in North America.

Bioclimatic model of Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) populations in Canada and the potential impacts of climate change

Abstract The northern Great Plains of North America has experienced a number of severe grasshopper infestations over the last 100 y. Grasshopper densities have been observed to be in synchrony over vast geographical areas. Weather is probably the most significant factor that affects fluctuations in population abundance of Melanoplus sanguinipes, the migratory grasshopper. Inferential modeling was used to develop a bioclimatic model of M. sanguinipes that closely agreed with current distribution and abundance patterns of this species in North America over a 30-y period. Incremental climate change scenarios were then applied to the bioclimatic model to predict changes to potential distribution and relative abundance of M. sanguinipes, resulting from climate change. Compared to predicted range and distribution under current climate conditions, model results indicated that M. sanguinipes would have increased range and relative abundance for temperature increases between 1 and 7°C. The model predicted that the range of this crop pest would be extended to regions that are not currently used for agricultural production in North America.

Bioclimatic analyses of distributions of a parasitoid Peristenus digoneutis and its host species Lygus spp. in Europe and North America.

1 Peristenus digoneutis Loan is a parasitoid of Lygus plant bugs, which was successfully introduced from Europe into North America in the 1980s for controlling native Lygus populations. Surveys confirmed that P. digoneutis populations have become established throughout eastern North America and that the spread of the parasitoid continues. For unknown reasons, previous releases of P. digoneutis in Western Canada were not successful. 2 A bioclimate (climex®; Hearne Scientific Software Pty Ltd, Australia) model for P. digoneutis in North America was developed, based on climate and ecological parameters, and then validated with actual distribution records. The current distribution of P. digoneutis in eastern North America was consistent with the predicted distribution. The model suggests that P. digoneutis will probably continue its spread westwards throughout the U.S.A. along the Great Lakes. 3 The southern distribution of P. digoneutis is expected to be limited by hot summer temperatures, whereas its northern range is limited by the number of Lygus host generations rather than cold stress. 4 Peristenus digoneutis has the potential to occur in the southern parts of the prairie ecozone of western Canada; however, Ecoclimatic Index values in the prairies indicate mainly marginal or unfavourable conditions, which may explain why earlier releases of P. digoneutis in Western Canada failed.

Actual and Potential Distribution of Acrolepiopsis assectella (Lepidoptera: Acrolepiidae), an Invasive Alien Pest of Allium spp. in Canada

Abstract Acrolepiopsis assectella (Zeller), leek moth, is a widespread and common pest of species of Allium L. (Liliaceae) in the western Palaearctic subregion. The establishment of A. assectella in eastern North America has resulted in economic losses to garlic (Allium sativum L.), leek (Allium porrum L.), and onion (Allium cepa L.) growers, especially to organic producers in eastern Ontario and southern Quebec. Acrolepiopsis assectella was first recorded in the Ottawa area in 1993. By 2010, A. assectella had expanded its range into eastern Ontario, southwestern Quebec, Prince Edward Island, and New York. A bioclimate model, using CLIMEX simulation software, was developed to produce mapped results that closely approximated known distributions for A. assectella in central Europe. This model was then validated with recorded distribution records in eastern Europe, Asia, and North America. Model output predicted that A. assectella will readily survive in southeastern Canada and the eastern United States of America. Other areas potentially suitable for A. assectella include coastal regions of the Pacific Northwest, the interior of southern British Columbia, and north-central Mexico. The continued range expansion of A. assectella into other Allium-growing areas of eastern North America appears to be inevitable. Establishment in these areas presents the risk of substantial production losses to Allium spp. producers.

Impact of grasshopper feeding on selected cultivars of cruciferous oilseed crops

Abstract With the trend towards crop diversification, there has been a gradual increase in production of crucifer oilseed crops (canola and mustard) in the Prairie Ecozone of western Canada. Developments in germplasm of Brassica spp. and Sinapis alba L. have resulted in cultivars with improved drought resistance, making them more acceptable for production in arid regions of the prairies. This, in turn, has resulted in increased overlap in areas of grasshopper infestation and oilseed production. Grasshoppers are the most chronic insect pests of annual crops in the Prairie Ecozone. The primary threat to production of annual crops arises from migration of the hatchling populations into cropland from roadsides, headlands and field margins at the beginning of the growing season. As a result, grasshopper damage is most acute at the early stages of crop growth. In this study, the impact of early season grasshopper feeding on canola and mustard crops was quantified in field studies, 1996 to 1998. Immatures of Melanoplus sanguinipes (the lesser migratory grasshopper) were allowed to damage eight Brassicaceae cultivars and breeding lines of four species: Brassica juncea Czern (‘AC Vulcan’ and ‘J92-223’), B. napus (‘AC Excel’ and ‘Midas’), B. rapa (‘AC Parkland’ and ‘Echo’) and S. alba (‘AC Pennant’ and ‘Ochre’). The overall yields of defoliated plants were 27.8% less than those of control plants (p = 0.0001). Yield reductions were greatest for AC Excel (47%) and least for AC Vulcan (19.6%). The results are discussed in the context of grasshopper management strategies.