Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium, is a foliar disease of onion worldwide, and has recently become an important disease in the northeastern United States and Ontario, Canada. The symptoms begin as small, tan to brown lesions on the leaves that can progress to defoliate plants. Crop loss occurs through reduced photosynthetic area, resulting in smaller, lower-quality bulbs. Leaf necrosis caused by SLB also can compromise bulb storage, as green leaves are required for the uptake of sprout inhibitors applied prior to harvest. The pathogen can overwinter on infested onion residue and infected volunteer plants. Asymptomatic weedy hosts near onion fields may also be a source of inoculum. Production of ascospores of the teleomorph (Pleospora allii) peaks in early spring in northeastern North America, often before the crop is planted, and declines rapidly as daily mean air temperatures rise. Conidia are usually present throughout the growing season. Application of fungicides is a standard practice for management of the complex of fungi that can cause foliar diseases of onion in this region. Recent assessments have shown that populations of S. vesicarium in New York and Ontario are resistant to at least three single-site mode-of-action fungicides. Three disease prediction systems have been developed and evaluated that may enable growers to reduce the frequency and/or number of fungicide applications, but the loss of efficacious fungicides due to resistance development within S. vesicarium populations threatens sustainability. The lack of commercially acceptable onion cultivars with sufficient resistance to reduce the number of fungicides for SLB also limits the ability to manage SLB effectively. Integrated disease management strategies for SLB are essential to maintain profitable, sustainable onion production across eastern North America.

Diseases caused by Stemphylium vesicarium are an increasing problem in the major asparagus and onion production regions of eastern and central Canada. Replicated and repeated controlled environment and field trials were conducted in Ontario to assess the disease reaction of asparagus and onion cultivars to determine if isolates from one crop can cross-infect other hosts, to assess the variation of disease symptoms among cultivars of onion and of asparagus, and to assess the ability of the pathogen to survive in a non-host species. All of the varieties of asparagus and onion assessed were susceptible to infection by S. vesicarium. There were small differences in susceptibility among varieties and in aggressiveness among isolates. These differences were not strongly associated with host crop. Onion cultivars that developed higher numbers of lesions often had lower levels of leaf dieback and vice versa. This indicated that resistance to infection was independent of susceptibility to development of dieback symptoms. In asparagus, infection on spears was not consistently correlated with severity on ferns. All isolates from asparagus and onion produced typical symptoms on wounded, but not unwounded, pear fruit. Finally, the pathogen was shown to colonize and sporulate on necrotic leaves of autumn rye, which is often used as a cover crop in asparagus fields. Stemphylium vesicarium can cross-infect asparagus and onion.

Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium (Wallr.) E.G. Simmons, has become an important disease of onion (Allium cepa L.) in Ontario, Canada, and the northeastern USA in recent years. The disease presents as elongated lesions on the leaves and severe leaf dieback. The effect on yield is unclear, but the extensive leaf dieback limits uptake of sprout inhibitors that are applied to onion foliage prior to harvest. This can result in high losses in storage. There are no resistant commercial onion cultivars and growers apply foliar fungicides at 7–14-day intervals to manage the disease. Field trials to evaluate fungicide efficacy and disease-forecasting models were conducted at the Muck Crops Research Station, Holland Marsh, Ontario, from 2011 to 2019. Fungicide efficacy declined over the years. The disease-forecasting models reduced the number of fungicide spray applications, but none of the models, including calendar-based applications, reduced SLB severity. Seed treatments containing penflufen, combined with calendar-based fungicide applications, reduced SLB severity. Assessments of fungicide insensitivity in isolates collected locally in 2018 and 2019 demonstrated that 90% of isolates (n = 48) were insensitive to azoxystrobin (a QoI fungicide, FRAC 11) and 57% (n = 47) were insensitive to pyrimethanil (an AP fungicide, FRAC 9). Both fungicides are used extensively on onion in the Holland Marsh but are no longer effective against the population of S. vesicarium that is present in the region. Additional studies on the efficacy of seed treatments, fungicide insensitivity, and potential of biological fungicides are required.

For non-profit organizations relying on volunteers to operate, investigations into the motivations of volunteerism are critical to attract new volunteers and to support the current ones. This study looked at volunteerism in the not-for-profit project The SEED in Ontario, Canada, which is looking to address food insecurity through a new social enterprise project that will create value-added “upcycled” products from second-grade produce while offering training opportunities for youth facing barriers to employment. The aims of this paper were to explore why volunteers chose to offer their time to this project and to gauge the current volunteers’ interest in volunteering with the organization’s new “Upcycle Kitchen”. Thirty-seven volunteers responded to a self-administered survey. They reported altruism, self-development, and social life improvement as their main motivations for volunteering. The volunteers expressed enthusiasm toward the Upcycle Kitchen initiative, which seems to be attributable to the multidimensional, creative, and educational aspects of the project. Tackling food insecurity and reducing the environmental impact of food waste are values which would most likely influence the respondents’ willingness to volunteer in food upcycling activities. We believe that this study is a good model to learn about the many facets of volunteerism for social enterprises developing upcycling-based food projects.

The fungal genus Stemphylium (phylum Ascomycota, teleomorph Pleospora) includes plant pathogenic, endophytic, and saprophytic species with worldwide distributions. Stemphylium spp. produce prodigious numbers of airborne spores, so are a human health concern as allergens. Some species also produce secondary metabolites, such as glucosides, ferric chelates, aromatic polyketides, and others, that function as toxins that damage plants and other fungal species. Some of these compounds also exhibit a low level of mammalian toxicity. The high production of airborne spores by this genus can result in a high incidence of human exposure. Concern about toxin production appears to be the reason that Stemphylium vesicarium, which is a pathogen of several vegetable crops, was classified in Canada as a potential risk of harm to humans for many years. A detailed assessment of the risk of exposure was provided to the relevant regulatory body, the Public Health Agency of Canada, which then determined that Stemphylium spp. in nature or under laboratory conditions posed little to no risk to humans or animals, and the species was re-assigned as a basic (level 1) risk agent.

There is a lack of information comparing UV-B radiation conidial sensitivity of the biocontrol agent Clonostachys rosea (Cr) and its target pathogen, Botrytis cinerea (Bc). We investigated the interactions in vitro and on strawberry leaf discs between previously selected Cr and Bc strains tolerant to UV-B radiation. Strawberry leaf discs inoculated with Bc, Cr, or combinations of both fungi were exposed to UV-B doses (2.9, 5.9, and 8.9 kJ m⁻²). Incidence and sporulation of both fungi were evaluated, and the Area Under Incidence Progress Curve (AUIPC) and Area Under Sporulation Progress Curve (AUSPC) were calculated. AUIPC and AUSPC of Cr on leaf discs were negatively correlated to increased UV-B. When inoculated alone on leaf discs, Bc was not affected by UV-B, but when inoculated with Cr the incidence and sporulation of Bc were positively correlated to UV-B radiation dose. In the absence of UV-B, Cr reduced incidence and sporulation of Bc. However, the ability of Cr to control Bc was reduced by 20% to 50% with increasing UV-B radiation. Increasing the applied concentration of Cr conidia 10-fold partially overcame the deleterious effects of UV-B on the ability of the biocontrol agent to reduce Bc sporulation in strawberry leaves. The selection of antagonists must fulfil many requirements; besides being active against the specific targeted plant pathogens, they must be cost-effective and have ecological characteristics suitable for the desired use conditions. We suggest that UV-B exposure must be taken into account during the development of bio-fungicides based on Cr.