Respondent demographic

In total, 15 respondents producing certified organic vegetables completed the online survey. However, the total number of respondents varied between each question. All participants who responded to the survey actively farmed in Wisconsin. The average age of grower respondents was 43, with 64% of respondents identifying as female and 47% having more than 11 yr of operating their farm. The respondents of the survey had significant formal education, with 93% of respondents (n = 14) holding a 4-yr college degree or higher. Many growers had farming backgrounds or experience with agriculture. Forty-three percent of organic growers (n = 14) had direct experience either growing up on a farm or working on a farm and 21% of growers had taken classes focused on agricultural production and management. These demographics are similar to national averages for organic farmers reported in the United States Department of Agriculture Census [USDA National Agricultural Statistics Service (NASS), 2017, 2019; Cushman, Reference Cushman2019].

Late blight is an important disease concern

Respondents were asked to rank the importance of several diseases to their tomato production, including anthracnose (Colletotrichum spp.), bacterial leaf spot (Xanthomonas campestris pv. vesicatoria), early blight (Alternaria solani), Fusarium (Fusarium oxysporum) and Verticillium wilt (Verticillium dahliae), late blight (P. infestans), leaf mold (Passalora fulva), mosaic virus (Tobamovirus), nematodes (Meloidogyne spp.) and septoria leaf spot (Mycosphaerella populorum). The top three most important diseases rated by growers was early blight, followed by septoria and late blight (Table 1). In addition to late blight being among the top three important tomato diseases, some growers noted the presence of this disease on their farms. Five out of 14 growers indicated that late blight had been diagnosed and confirmed by an Extension agent or disease clinic over the past 10 yr on their farm. These data suggest that late blight is a disease concern for organic tomato producers in Wisconsin.

Table 1.

Topmost important tomato diseases

The number of organic growers that rated each disease as the most extremely important disease of their tomato production is indicated by ‘Count’. Total number of respondents for each disease is indicated by ‘Total N’. Percentages represent the percent of organic growers who rated each disease as extremely important.

Cultural strategies rank highly as a late blight management strategy

Growers were asked to rank the importance of several strategies for late blight management, from ‘not at all important’ to ‘extremely important’, on a five-part Likert scale (Table 2). The top two strategies ranked ‘extremely important’ based on percentage of organic respondents out of total respondents included crop diversity (eight out of nine, 89%) and organically approved fungicides (four out of five, 80%) (Table 2). The importance of crop diversity as a management approach reflects the systems-based management strategies promoted by the USDA National Organic Program Federal regulations, which emphasize practices such as crop rotation and diversity to increase biodiversity and conserve wetlands, woodlands and wildlife (USDA, 2014). Eleven growers ranked crop rotation as their most important management strategy (Table 2). The frequent identification of crop rotation and crop diversity among the responses to this question which specifically referenced their management strategies regarding late blight may indicate that organic growers correlate these approaches with successful mitigation of the late blight pathogen. However, this association may suggest a gap in knowledge about late blight pathogen biology, as P. infestans is not soilborne in the USA and thus its airborne spread cannot be effectively managed through crop rotation and diverse crop plantings (Finckh et al., Reference Finckh, Schulte-Geldermann and Bruns2006; Speiser et al., Reference Speiser, Tamm, Amsler, Lambion, Bertrand, Hermansen, Ruissen, Haaland, Zarb, Santos, Shotton, Wilcockson, Juntharathep, Ghorbani and Leifert2006; Islam et al., Reference Islam, Mondal, Hossain and Meah2013; Goutam et al., Reference Goutam, Thakur, Salaria and Kukreja2018; Haveri et al., Reference Haveri, Reddy and Thulasiram2018; Khan et al., Reference Khan, Ghazanfar and Raza2019). The ranking of ‘extremely important’ with respect to the use of organically approved fungicides suggests growers are aware of the limitations of cultural management strategies against late blight. Given this knowledge of late blight and the understanding that a key tenant of organic systems involves managing production using an ecological approach (Shahi et al., Reference Shahi, Kachhap, Kumar, Agarwal and Singh2021), growers may be broadly applying strategies that most align with systems-based management principles regardless of pathogen biology and etiology. Further information regarding grower decision-making and specificity toward different pathosystems is needed to better inform education efforts.

Table 2.

Extremely important late blight management strategies

The number of organic growers who rated each of the following late blight management strategies as ‘extremely important’: resistant varieties, soil fertility management, crop timing, crop rotation, crop diversity, sanitation, tillage, mulching, irrigation, pest prediction tools, information about outbreaks, scouting, organically approved fungicides and compost teas/plant growth enhancers is indicated by ‘Count’. The total number of respondents for each factor is indicated by ‘Total N’.

Factors influencing late blight management

Growers also ranked the importance of several factors that influence their use of late blight management strategies from ‘not at all important’ to ‘extremely important’ (Table 3). Organic growers were highly influenced by yield maximization (five out of seven, 71%), soil health (10 out of 14, 71%) and product availability (five out of seven, 71%). While yield maximization and product availability were ranked highly, most growers highlighted the impacts on soil health as extremely important in influencing their disease management decisions. The importance of soil health aligns with the requirements and goals of the USDA National Organic Program regulations, which emphasize maintenance or enhancement of soil and water quality (Fernandez-Cornejo et al., Reference Fernandez-Cornejo, Greene, Penn and Newton1998; USDA, 2002, 2016; Burchard, Reference Burchard2005; Kuepper, Reference Kuepper, McDermott and Harris2013; Paull, Reference Paull2014). Other health-related factors emphasized by organic growers within their decision-making frameworks included pollinator health, maintenance of beneficial microbes and worker safety (Table 3). When asked about their motivations for farming organically, most responses included human and environmental health. For example, one grower said, ‘I am trying to protect my customers and the environment from chemicals that are harmful’ and another said, ‘Organic farming is an ethical choice’ and ‘Environmental health and people[‘s] health compel[s] me to farm organically’. Other responses listed ‘market demand’ and ‘to produce good tasting produce that delights when consumed’. The health of the environment, pollinators, microbes, workers and consumers have been identified as important drivers of organic and diversified farm management systems (Kelemen et al., Reference Kelemen, Nguyen, Gomiero, Kovács, Choisis, Choisis, Paoletti, Podmaniczky, Ryschawy, Sarthou, Herzog, Dennis and Balázs2013; Kuepper, Reference Kuepper, McDermott and Harris2013; Bhavsar, Reference Bhavsar2017) and should be considered when evaluating not only the suitability of new practices and products for use under certified organic management, but also in the communication of how these practices advance the ability of organic growers' to achieve their systems-based health goals.

Table 3.

Extremely important factors influencing late blight management strategies

The number of organic growers who rated the following factors as ‘extremely important’ in influencing late blight management: profit maximization, yield maximization, resistance management, soil health, pollinator health, maintenance of beneficial insects, maintenance of beneficial microbes, product cost, product availability, labor cost, labor availability, worker safety, knowledge of application and availability of application tools is indicated by ‘Count’. Total number of respondents for each factor is indicated by ‘Total N’.

Copper and reduced risk biopesticides with organic late blight management

In addition to cultural and variety selection strategies, reduced risk pesticides are especially salient within the discussion of managing high-risk tomato diseases, such as late blight. Growers were queried about their perceptions and usage of organically approved fungicides. These included copper products as well as biopesticides, which were defined as an oil, plant or naturally derived product that controls pests or pathogens by inhibiting or eliminating them.

Overall, use of copper fungicides was limited among survey respondents. Three out of nine growers used copper products (Table 4), with respondents citing concerns with copper's ‘off-target effects’, ‘worker safety’, ‘build-up’, ‘exposure’ and ‘residue’. These same concerns at the regulatory level have led to increasing restrictions on copper use in certified organic systems (INRA Science and Impact, 2019). Due to copper's adverse effects on soil and water quality, copper use for crop protection in both conventional and organic systems is completely banned in some northern European countries, leading to increasing need to identify copper-alternative biopesticide products (INRA Science and Impact, 2019; La Torre et al., Reference La Torre, Righi, Iovino and Battaglia2019; La Torre et al., Reference La Torre, Righi, Iovino and Battaglia2019).

Table 4.

Use of biopesticides

The number of organic growers who use non-copper and copper pesticides are indicated by ‘Count’. Total number of respondents for each type of product is indicated by ‘Total N’.

To further understand Wisconsin organic vegetable grower concerns of copper, respondents were asked to rank common statements about copper on a Likert scale from ‘not at all concerning’ to ‘extremely concerning’ (Fig. 1). Fifty percent (n = 14) of growers responding to the survey were extremely concerned regarding copper's harm to the environment and humans, with 43% (n = 15) of growers indicating concerns about residues on the harvested fruit, which can affect marketability due to consumer health concerns and negative cosmetic appearance (Baker et al., Reference Baker, Benbrook, Groth and Benbrook2002; Lamichhane et al., Reference Lamichhane, Osdaghi, Behlau, Köhl, Jones and Aubertot2018). Thirty-six percent (n = 14) of growers indicated that the difficulty of finding alternatives to copper was very concerning. Additionally, challenges with respect to lack of information regarding copper product alternatives, including the expense of these alternatives, were concerning for 15% (n = 14) and 23% (n = 15) of respondents, respectively. Regarding efficacy, copper was rated only slightly more effective than non-copper biopesticides with 38% (n = 13) of growers rating copper as ‘effective’ and ‘very effective’ compared to 35% (n = 14) rating non-copper biopesticides as ‘effective’ and ‘very effective’ (Fig. 1). This finding was surprising, as results of replicated research conducted in laboratory field, and growth chamber studies have consistently demonstrated copper as the most efficacious crop protectant in organic systems for tomato late blight (Dorn et al., Reference Dorn, Musa, Krebs, Fried and Forrer2007; Mizubuti et al., Reference Mizubuti, Lourenço and Gregory2007; Wang et al., Reference Wang, Hu, Zhang, Forrer and Cao2007; Hansen et al., Reference Hansen, Everts, Fry, Gevens, Grünwald, Gugino, Johnson, Johnson, Judelson, Knaus, McGrath, Myers, Ristaino, Roberts, Secor and Smart2016; Lamichhane et al., Reference Lamichhane, Osdaghi, Behlau, Köhl, Jones and Aubertot2018). However, a greater percentage of growers (54%, n = 13) was unsure about the effectiveness of copper, reflecting the broader lack of research regarding organic disease management, as well as a dearth of education materials specifically aimed toward the pest management needs of organic vegetable farmers. Concerns about environmental/human health impacts and product residues, coupled with issues identifying effective alternative products, strongly contribute to the risks and limitations associated with copper and may have influenced the low number of respondents who reported using copper in their disease management programs.

Fig. 1.

Grower concerns about copper products. Percentage of organic growers who ranked concern of statements about copper products from not at all concerning to extremely concerning. Total number of respondents that responded to each statement is indicated by N.

Usage and concerns of non-copper biopesticides

With the push toward reduction of copper use for disease management, non-copper biopesticides are becoming an increasingly attractive alternative in organic vegetable production. Interest in incorporating biopesticides into organic disease management programs has increased due, in part, to the products' biodegradability, low residual presence in the environment, low resistance risks, ability to specifically target pests and pathogens, little to no off-target effects and durability of disease management programs while protecting yield (Seiber et al., Reference Seiber, Coats, Duke and Gross2014; Tripathi et al., Reference Tripathi, Upadhyay, Bhuyan and Battacharya2009; Damalas and Koutroubas, Reference Damalas and Koutroubas2018; Marrone, Reference Marrone2019; Kalpana and Anil, Reference Kalpana and Anil2021). Furthermore, biopesticides can be used to reduce synthetic pesticide use and act as a pest resistance management strategy (Butu et al., Reference Butu, Stef, Grozea, Corneanu, Butnariu, Hakeem, Bhat and Qadri2020; Essiedu et al., Reference Essiedu, Adepoju and Ivantsova2020). We found that most organic growers responding to the survey (five out of six) have used non-copper biopesticides compared to copper products (Table 4). Despite this high degree of adoption of these productions, concerns regarding non-copper biopesticides included ‘uncertainty in mode of action and efficacy’, ‘high cost’ and ‘rainfastness’ (the degree to which the pesticide can be effective after rainfall or irrigation), with half of the growers responding to the survey uncertain about the efficacy of non-copper biopesticide products (50%, n = 14) (Fig. 2). These findings suggest that, with clearer information regarding the specific efficacy of biopesticide inputs, alternatives to copper could be more widely adopted into organic disease management programs. This further highlights the need for more replicated trials to determine modes of action and efficacy across greater ranges of environments and inoculum pressures to guide the development and communication of best management practices which would facilitate the successful integration of these products within disease management plans.

Fig. 2.

Perceived effectiveness of organic products. Percentage of organic growers who rated effectiveness of copper and non-copper biopesticides from not at all effective to very effective. Total number of respondents who rated each type of product is indicated by N.

Live audience response survey corroborated online survey results

Results from the live audience response survey corroborated findings from the online Qualtrics survey. Most respondents at the 2019 MOSES conference had experience working on a farm (44%, n = 78) and farmed in Wisconsin, Minnesota and Illinois. Farmers' experiences ranged from no organic experience to 40 yr, with an average of 7.6 yr. This group had similar variance in organic production experience as the online survey respondents, but had slightly lower average experience compared to the online survey averaged experience of 12.3 yr.

As with the online survey, growers reported fungal and fungal-like organisms as the most concerning pathogen group affecting organic tomato production (65%, n = 39). Once again, many growers noted concern regarding true fungal diseases such as septoria and early blight, which are caused by debris-borne pathogens and persist annually (Kemmitt, Reference Kemmitt2002; Zitter, Reference Zitter2020). In comparison, late blight, while occurring annually in the region, is not always guaranteed to occur annually on a given farm and thus growers prioritize their management efforts toward persistent and annually occurring diseases. Although late blight was not the primary concern for organic growers, most respondents from the audience indicated experiencing late blight on their organic farm (63%, n = 38), with 37% (n = 22) responding that they actively manage for late blight.

Respondents were asked to choose the three most important approaches emphasized when managing late blight. They were allowed to select up to three choices and the maximum allowed recorded responses was 100. Like the online survey results, crop rotation was the most important management approach, with 31% of respondents (n = 100) indicating this as their primary tool. This was followed by resistant varieties (20%) and organically approved fungicides (16%). Respondents' use of copper and non-copper products were less than 40% (n = 47). Nearly half of the respondents (43%, n = 20) indicated they do not use pesticides to manage late blight. For growers that use fungicides to manage late blight, a follow-up question about the greatest limitations to using these products was asked. Like the online survey results, product cost and knowledge of application (explained to the respondents as product mode of action or protocol for application) were the top two greatest limitations at 26 and 15%, respectively (n = 47). When asked if they had used biopesticides within their disease management programs, a majority (62%, n = 47) responded ‘no’, again reflecting the findings from the online survey. For those that used biopesticides, respondents listed specific products used, which included (1) copper products such as Champ (copper hydroxide) and Cueva (copper octanoate), (2) microbial products such as Serenade (Bacillus subtillis) and Actinovate (Streptomyces lydicus), (3) plant extracts such as Regalia (Reynoutria sachalinensis) and (4) essential oils such as EF400 (blend of clove, rosemary, peppermint oils) (n = 25). As a follow-up question, we asked about their satisfaction regarding efficacy and 50% (n = 21) indicated they were unsatisfied, unsure or experienced variable satisfaction with these products, corroborating the findings from the online survey. These responses indicate the potential for future research and education programs to address these concerns in efficacy and modes of action, which in turn could result in enhanced organic grower decision-making regarding biopesticide products. Furthermore, greater knowledge of biopesticides can reduce grower risk aversion of implementing these products into integrated disease management programs. This is especially critical in management programs targeting diseases that require preventive crop protections (Moser et al., Reference Moser, Pertot, Elad and Raffaelli2008; Chandler et al., Reference Chandler, Bailey, Tatchell, Davidson, Greaves and Grant2011; Islam et al., Reference Islam, Mondal, Hossain and Meah2013). The integration of biopesticides as a preventive tool in integrated disease management is particularly pertinent in high-risk disease situations, such as late blight, where any detection of symptoms on the plant indicates that crop loss and potential spread has already occurred (Gevens et al., Reference Gevens, Seidl and Hudelson2010; McGrath, Reference McGrath2010; Haveri et al., Reference Haveri, Reddy and Thulasiram2018). Moreover, biopesticides can have an important role in the effective management of diseases which are spread aerially, which may limit the effectiveness of crop rotation and crop diversity in disease mitigation and further necessitate preventive management strategies that include inputs (Van Bruggen and Termorshuizen, Reference Van Bruggen and Termorshuizen2003; Van Bruggen et al., Reference Van Bruggen, Gamliel and Finckh2016; Rawat et al., 2021).

Resources used by respondents

From a list of sources of information, including University of Wisconsin Extension, Midwest Organic and Sustainable Education Service (MOSES), other farmers, books/magazines, published scientific research, resources on the internet and workshops/field days/conferences, growers were asked to rank how often they used each resource from ‘never’, ‘1–2 times’, ‘3–5 times’ and ‘more than 5 times’ over the past 10 yr. The top two most cited resources used were resources on the internet and other farmers. It was not defined what was included in ‘resources on internet’, which may have included Extension sources as well as resources from other organic-focused non-profit education organizations. Resources specifically identified from UW Extension were accessed by the respondents, but those that used this resource tended to use them less frequently. This contrasts with the frequency of use of the resources provided by a non-profit organic-focused organization based in the upper Midwest, MOSES, whose resources were accessed by most farmers (88%) using this resource over five times in the last 10 yr. This suggests that the university Extension services have an opportunity to expand their engagement and impact within the organic vegetable farming community through provided resources that can be tailored to organic farmers' goals and systems. Furthermore, the identification of other farmers as primary resources indicates that integrating growers as co-educators into organic programming can enhance the impact of these programs by building trust, relevance and credibility (Wyckhuys and Oõneil, Reference Wyckhuys and Oõneil2007; Kuehne et al., Reference Kuehne, Llewellyn, Pannell, Wilkinson, Dolling, Ouzman and Ewing2017; Bardenhagen et al., Reference Bardenhagen, Howard and Gray2020). Increasing these bidirectional modes of engagement between Extension agents and organic growers as co-educators and co-creators of knowledge has been identified as a method to not only improve Extension resources for organic production, but also positively influence the communication and adoption of effective preventive pest management strategies within organic systems (Sarker and Itohara, Reference Sarker and Itohara2009; Bardenhagen et al., Reference Bardenhagen, Howard and Gray2020; Marabesi et al., Reference Marabesi, Kelsey, Anderson and Fuhrman2021). Thus, university Extension programs may be improved by developing research, workshops, conferences, and resources in close partnership with grower stakeholders (Table 5).

Table 5.

Resources used by growers for farm management

Percentage of organic growers who used the following resources for their farm management more than five times over the past 10 yr (2007–2017): University of Wisconsin-Madison Extension (UW-Madison Extension), Midwest Organic and Sustainable Education Service (MOSES), other farmers, books/magazines, published scientific research, resources on the internet and workshops/field days/conferences. The number of organic growers who used listed resources is indicated as ‘Count’. Total number of respondents who rated each type of resource is indicated by N.