A. Boilard, and A. Duclos for their help in the lab and in the field. We thank M.-P. Lamy, C. Roy, G. Ayotte, and M. Paquet for their assistance in identifying flowers. We are also indebted to A. Beaudoin and É. Duchemin for logistic support, and to S. McIvor and J.-P. Lessard for their constructive comments on a previous version of the manuscript. Finally, special thanks to the managers of cemeteries and community gardens as well as the Management of Large Parks and Greening of the city of Montreal for allowing access to their sites. This study was funded by the National Science and Engineering Research Council of Canada (NSERC) Discovery Grant Program and the Fonds de Recherche Nature et Technologies Québec (FRQNT). The Bayesian analyses and goodness of fit tests were conducted on the Graham high performance computer clusters of Compute Canada.

Climate change is reshaping agriculture and insect biodiversity worldwide. With rising temperatures, insect species with narrow thermal margins are expected to be pushed beyond their thermal limits, and losses related to herbivory and diseases transmitted by them will be experienced in new regions. Several previous studies have investigated this phenomenon in tropical and temperate regions, locally and globally; however, here, it is proposed that climate change impact on agriculture can be traced through the study of Nearctic migratory insects, specifically leafhoppers. To test this hypothesis, leafhoppers in strawberry fields located in the province of Québec, eastern Canada, were evaluated. The strawberry-leafhopper pathosystem offers a unique opportunity because leafhoppers can transmit, among other diseases, strawberry green petal disease (SbGP), which is associated with pathogenic phytoplasmas. Here, we found that in the last ten years, the number of leafhoppers has been increasing in correspondence with the number of SbGP cases detected in eastern Canada, reporting for the first time ten species new to eastern Canada and two to the country, although the leafhopper diversity has been seriously affected. Our model using more than 34 000 leafhoppers showed that their abundance is influenced by temperature, a factor that we found also influences the microbiome associated withMacrosteles quadrilineatus, which was one of the most abundant leafhoppers we observed. One of our most striking findings is that none of the insecticides used by strawberry growers can control leafhopper incidence, which could be linked to microbiome changes induced by changing temperatures. We suggest that Nearctic leafhoppers can be used as sentinels to trace the multilayered effects of climate change in agriculture.

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The foxglove aphid, Aulacorthum solani (Kaltenbach) (Hemiptera: Aphididae), and the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), are among the serious insect pests found in greenhouses. The efficacy of microbial control against these insects has been demonstrated and can be enhanced by the combination of different microbial agents. This study evaluated the efficacy of Bacillus pumilus Meyer and Gottheil PTB180 and Bacillus subtilis (Ehrenberg) Cohn PTB185, used alone and together, to control these two aphids both in the laboratory and in greenhouse on tomato, Solanum lycopersicum Linnaeus (Solanaceae), and cucumber, Cucumis sativus Linnaeus (Cucurbitaceae), plants. The results from the laboratory tests showed an increase in mortality induced by all biological treatments. In the greenhouse, all treatments induced mortality rates significantly higher than that of the control for A. solani. Similarly, all treatments performed better than the control against A. gossypii, significantly reducing its reproduction. Furthermore, we found no additive effects when mixing products nor negative interactions affecting survival for the bacteria investigated. These microorganisms therefore have potential for use in biological control.

The main objective of this study was to inventory the abundance and species richness of wild bees and hoverflies in the Lac Saint-Pierre floodplain according to a land-use gradient. In 2019 and 2020, pollinators were sampled using pan-traps in three landscape types: Crop field margins, Perennial hayfields, and Natural habitats. Bee and hoverfly populations were dominated by a few species throughout the study area. Crop field margins contained greater floral availability and attracted more individuals and species of bees than other landscape types. Although hoverflies were not affected by either land-use type or flooding, the abundance and species richness of bees appeared to be reduced when spring flooding lasted longer, suggesting a mortality effect of flooding on their populations.