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AbstractOrange wheat blossom midge, Sitodiplosis mosellana(Géhin) (Diptera: Cecidomyiidae), has been successfully reared in the laboratory for more than 20 years in Winnipeg, Manitoba, Canada. The rearing method has been developed to the point where it efficiently produces large numbers of wheat midge continuously under laboratory conditions for use in experiments on wheat midge biology and for screening wheat lines for crop resistance. Adult survival was extended by providing high humidity, and oviposition was increased by simulating natural dawn and dusk conditions and by supplying preflowering spring wheat to adults. Preventing desiccation of the wheat midge larvae in the wheat spikes before overwintering in soil and providing optimal cold conditions for a long enough period to break larval diapause enabled successful adult emergence. We provide data to facilitate the coordination of timing of wheat midge emergence from diapause with the wheat susceptible period. The method can be readily scaled up for screening many lines for resistance or scaled down for small experiments. Here, we report details of the rearing method so that others can implement it for research on the management of this internationally important pest.

Some plant pathogens are capable of manipulating their insect vectors and plant hosts in a way that disease transmission is enhanced. Aster leafhopper (Macrosteles quadrilineatusForbes) (Hemiptera: Cicadellidae) is the main vector of Aster Yellows Phytoplasma (CandidatusPhytoplasma asteris) in the Canadian Prairies, which causes Aster Yellows (AY) disease in over 300 plant species including cereals and oilseeds. However, little is known about the host range of Aster leafhoppers or their host-choice selection behavior in this geographical region. Several crop and noncrop species commonly found in the Canadian Prairies were evaluated as food and reproductive hosts for Aster leafhoppers through no-choice bioassays. To study possible effects of pathogen infection, AY-uninfected and AY-infected insects were used. Cereals and some noncrops like fleabane were suitable reproductive hosts for Aster leafhoppers, with numbers of offspring observed in treatments using both AY-uninfected and AY-infected insects, suggesting an egg-laying preference on these plant species. Development was similar across the different plant species, except for canola and sowthistle, where growth indexes were lower. Sex-ratios of Aster leafhopper adults did not differ among the plant species or with respect to AY infection. Potential fecundity differed across plant species and was affected by the infection status of the insect. These findings have implications for AY epidemiology and suggest that while cereals can be suitable host plants for Aster leafhopper oviposition and development, some noncrop species could act as alternate hosts for leafhoppers that migrate into the Canadian Prairies before emergence of cereal and canola crops.

In agricultural areas, the climatic conditions at the northern limit of crop cultures could impact pest regulation. In this paper, we study the aphid-parasitoid-hyperparasitoid network in cereal fields around Saskatoon (SK, Canada), one of the most harsh climatic conditions for cereal crops in the world, with an extremely short growing season. We have investigated the aphid-parasitoid-hyperparasitoid species relative abundances over two consecutive years. In 2014, a cold spring year, aphids were only found late in the growing season, and their arrival probably corresponded to late Southern winds. In 2015, aphids, parasitoids and hyperparasitoids arrived in the cereal fields in July and August, whereas the cereal harvest is typically complete by the end of the month of August. Three species of primary parasitoids were found for a total parasitism rate of 7.62%, and four genera of hyperparasitoids, with a hyperparasitism rate of 20.1%. There were 87.4% apterous aphids, and the proportion of apterous and winged (alate) aphids did not differ among the 3 aphid species, or among use by parasitoid species and hyperparasitoid species. The sex ratio of parasitoids in the complex was biased towards females for most of the species. In areas with extreme weather conditions and short growing seasons, effective biocontrol through parasitism is limited, although the synchronization level of parasitoids to their aphid hosts is high. We discuss the consequences of the limited length of the growing season on the provision of ecosystem services and on the seasonal ecology of insects of agronomic interest. We also provide information about morphological criteria for identification of parasitoids from the genus Aphidius.

AbstractQuinoa, Chenopodium quinoaWilldenow (Amaranthaceae), cultivation has expanded beyond its historical range in South America into Europe and North America due to its high nutritional properties for human consumption. With the introduction of a crop into a novel range comes the potential for insect pest issues. Here, using traditional morphology and DNA barcoding we identify larvae of Scrobipalpa atriplicella(von Röslerstamm) (Lepidoptera: Gelechiidae), an introduced Eurasian moth, feeding on quinoa throughout the Prairie region of western Canada. Larvae can feed within the stem, on foliage, and directly on seed within the panicles, which can result in up to a 100% yield loss. We summarise distinguishing adult characteristics, potential host plants, and give initial remarks on the life cycle of this moth and its known host range in Canada. The potential for high yield losses makes further investigation of S. atriplicellaa priority to maintain and expand sustainable quinoa production in Canada.

AbstractOver the past 20 years, ash trees (Oleaceae) in parts of the western United States of America and Canada have been subject to infestations with the psyllid Psyllopsis discrepans(Flor) (Hemiptera: Psyllidae). Infested trees show a series of symptoms, including pseudogalls, canopy loss, and in many cases, tree death. This is an expensive problem for urban forests, particularly in the context of emerald ash borer (Coleoptera: Buprestidae) and Dutch elm disease (Ophiostomataceae), which also impact the diversity of urban forests. This paper presents results from a study on the efficacy of two tree-injected insecticides, Orthene® (acephate) and TreeAzin® (azadirachtin). Trees were treated with these insecticides, and egg and adult psyllids were counted. In addition, canopy cover and severity of pseudogalling were visually assessed. Orthene reduced canopy loss and severity and amount of pseudogalling compared to what occurred on control trees; however, there were more eggs on Orthene-treated trees, indicating that any potential benefit was offset by higher egg counts after treatment. Due to the rapid decline of the ash trees, TreeAzin could not be successfully injected.

Inflorescences (heads or capitula) of the putative self-incompatible species, purple coneflower (Echinacea angustifolia (DC) Cronq. (Asteraceae)), were visited by insects representing the Coleoptera, Diptera, Hymenoptera, and Lepidoptera, in accordance with a generalist pollination syndrome. Measurement of the effectiveness of insect species as pollinators was accomplished by permitting solitary visits to receptive, central disc florets of virgin (previously bagged) heads. Four parameters were quantified: total stigmatic pollen load and proportion of pollen grains germinated, numbers of pollen tubes at style bases, and percentages of total receptive florets that had retracted (shrivelled) styles. Quantifying total and germinated pollen grains proved ineffective, partly owing to the tendency of self-pollen to initiate pollen tubes. The most effective pollinators were Apidae, especially bumble bees (Bombus spp.) and the European honey bee (Apis mellifera L.) (mean: 39–61% of styles retracted). Other noteworthy pollinators were cloudless sulfur butterflies (Phoebis sennae L.—Pieridae; mean 47% of style bases with pollen tubes), golden blister beetles (Epicauta ferruginea Say—Meloidae; 44%), and grasshopper bee flies (Systoechus vulgaris Loew—Bombyliidae; 22%). Sunflower leafcutter bees (Megachile pugnata Say) were less effective (4% of styles retracted). Promisingly, analysis of the proportion of retracted styles provided similar results to the established technique of pollen-tube quantification, but had the significant advantages of being completed more rapidly, without a microscope, and in the field. The quantitative technique of retracted-style analysis appears well suited for prompt measurement of inflorescence-visiting insects as pollinators of many asteraceans.