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.

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is one of the most devastating diseases affecting the canola/oilseed rape (Brassica napus) industry worldwide. Currently, the planting of clubroot-resistant (CR) cultivars is the most effective strategy used to restrict the spread and the economic losses linked to the disease. However, virulent P. brassicae isolates have been able to infect many of the currently available CR cultivars, and the options to manage the disease are becoming limited. Another challenge has been achieving consistency in evaluating host reactions to P. brassicae infection, with most bioassays conducted in soil and/or potting medium, which requires significant space and can be labor intensive. Visual scoring of clubroot symptom development can also be influenced by user bias. Here, we have developed a hydroponic bioassay using well-characterized P. brassicae single-spore isolates representative of clubroot virulence in Canada, as well as field isolates from three Canadian provinces, in combination with canola inbred homozygous lines carrying resistance genetics representative of CR cultivars available to growers in Canada. To improve the efficiency and consistency of disease assessment, symptom severity scores were compared with clubroot evaluations based on the scanned root area. According to the results, this bioassay offers a reliable, less expensive, and reproducible option to evaluate P. brassicae virulence, as well as to identify which canola resistance profile(s) may be effective against particular isolates. This bioassay will contribute to the breeding of new CR canola cultivars and the identification of virulence genes in P. brassicae that could trigger resistance and have been very elusive to this day.

Strawberry green petal disease is a serious disease affecting strawberry plants in the Americas, Europe, and Australia. Strawberry green petal disease is caused by ‘Candidatus Phytoplasma asteris’-related strains, ‘Ca. P. hispanicum’-related strains, and ‘Ca. P. australiense’-related strains. This diagnostic guide provides details about the symptomatology, distribution, and molecular diagnosis of strawberry green petal disease that will help with detection and identification of the disease in fields and in the laboratory.

Climate change is impacting agriculture in many ways, and a contribution from all is required to reduce the imminent loses related to it. Recently, it has been showed that citizen science could be a way to trace the impact of climate change. However, how can citizen science be applied in plant pathology? Here, using as an example a decade of phytoplasma-related diseases reported by growers, agronomists, citizens in general, and confirmed by a government laboratory, we explore a new way of valuing plant pathogens monitoring data deriving from land-users or stakeholders. Through this collaboration we found that in the last decade thirty-four hosts have been affected by phytoplasmas, nine, thirteen and five of these plants were, for the first time, reported phytoplasma hosts in Eastern Canada, in Canada and worldwide, respectively. Another finding of great impact is the first report of a ′Ca. P. phoenicium′-related strain in Canada, while ′Ca. P. pruni′ and ′Ca. P. pyri′ was reported for the first time in Eastern Canada. These findings will have a great impact in the management of phytoplasmas and their insect vectors. Using these insect-vectored bacterial pathogens, we show the needs of new strategies that allow a fast and accurate communication between concerned citizens and those institutions confirming their observations.

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Climate change is impacting agriculture in many ways, and a contribution from all is required to reduce the imminent losses related to it. Recently, it has been shown that citizen science could be a way to trace the impact of climate change. However, how can citizen science be applied in plant pathology? Here, using as an example a decade of phytoplasma-related diseases reported by growers, agronomists, and citizens in general, and confirmed by a government laboratory, we are exploring how to better value plant pathogens monitoring data. Through this collaboration, we found that in the last decade thirty-four hosts have been affected by phytoplasmas, nine, thirteen and five of these plants were, for the first time, reported phytoplasma hosts in Eastern Canada, in Canada and worldwide, respectively. Another finding of great impact is the first report of a ‘Ca. P. phoenicium’-related strain in Canada, while ‘Ca. P. pruni’ and ‘Ca. P. pyri’ was reported for the first time in Eastern Canada. These findings will greatly impact the management of phytoplasmas and their insect vectors. Using these insect-vectored bacterial pathogens, we show the need for new strategies that can allow fast and accurate communication between concerned citizens and those institutions confirming their observations.

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Tomato (Solanum lycopersicum L.) is one of the most important vegetables in the world. Its extensive cultivation has made this plant the target of many viral, fungal, and bacterial diseases. Among them, the bacterial canker of tomato caused by Clavibacter michiganensis (Cm) has been named one of the most devastating diseases affecting the tomato industry worldwide. It can significantly reduce the yields and profitability of this crop. One of the big challenges we found when working with Cm and trying to characterize the virulence of different isolates was the lack of a consensus methodology to inoculate tomato plants, how to fertilize them and characterize Cm virulence. This research aimed to identify an artificial inoculation method to induce bacterial canker on tomato plants in greenhouse conditions to homogenize the results of different studies with Cm. We compared two inoculation methods, including the scalpel and syringe method with two levels of fertilization, low and high fertilization. After evaluating several variables like the percentage of necrotic leaves and the height of the plants, the results showed that the syringe inoculation with low fertilization was the most effective inoculation method allowing the development of a multilevel scale that can be used to study the interaction between tomato plants and Cm isolates.