Assessing the United States Grape Industry’s Understanding of Fungicide Resistance Mitigation Practices

Discussion

The U.S. grape industry members who responded to this survey recognized fungicide resistance as a serious-to-devasting problem within the country (68%; Figure 5), and indicated that it was a moderate-to-devastating problem within their own operations (55%; Figure 6). This provides a baseline indication that fungicide resistance, toward the mitigation of long-term effects of widespread resistance and ensuing crop losses, is a potentially growing area of educational need within the grape industry in the United States.

A critical player in developing information and resources on fungicide resistance management is the international FRAC (FRAC 2020). In our survey, over 67% of respondents were either moderately or extremely familiar with the acronym FRAC (Figure 1) and its importance for fungicide resistance management. The FRAC best practices define fungicides broadly, based on their biochemical mode of action, resistance development risk, and cross resistance pattern, rather than as individual active ingredients. A result of this process is the grouping of chemistries by a code, which creates a quick and easy reference for comparing chemistries. In our survey, 75% of respondents could identify the FRAC group of a fungicide, and primarily sourced that information from the product label (42%) (Figure 2). While it is impressive that the respondents can identify a product’s FRAC group, only 42% of survey respondents source that information from the label. For those who do not use the fungicide label to identify a FRAC group, it would be worth learning if they do not refer to the label at all, if they do not know that the FRAC group is listed on the label, or if they do not spend sufficient time reading through the label to find this information.

Respondents to this survey indicated they felt “moderately competent” designing fungicide programs that adhere to resistance management principles, and using the principles described by FRAC (Figure 3). This indicates that education efforts can be further advanced to focus on more complex topics such as how to incorporate integrated disease and resistance management into a practical fungicide program. This was re-emphasized in their responses to further questions on the importance of different mitigation practices, where they demonstrated a more advanced understanding of fungicide stewardship principles. This included the ability to recognize the distinction in importance of rotating between fungicide brand names and rotating between FRAC group(s) (Figure 7). A different brand name may or may not indicate that two products have unique active ingredients or that they belong to different FRAC groups. Survey respondents categorized rotating FRAC groups in a fungicide program as extremely important, but rotating brand names as only slightly important. This probably indicates that they have an understanding that product rotation recommendations focus on rotating FRAC groups, and that rotating based on brand names may not achieve the desired outcome. While they also recognized that not using the same brand name of fungicide back-to-back is very important, they ranked the similarly phrased statement of not using sequential applications of the same FRAC group as extremely important (Figure 7). The same pattern of response was seen when asked to rank the importance of mixing products—tank mixing brand names as a strategy for fungicide resistance mitigation was seen as being slightly important, but tank mixing different FRAC groups was seen as very important. Additionally, respondents ranked practices such as using multisite products, canopy management, sprayer calibration, and maintenance as extremely important (Figure 7).

These responses demonstrate a sophisticated level of understanding of the nuances of avoiding sequentially using fungicides with the same mechanism. However, knowing that a practice is important is not necessarily indicative that those practices would be subsequently applied (Hillis et al. 2017). Additional studies are needed to confirm whether these activities to mitigate fungicide resistance are routinely adopted or used in vineyards.

The survey further indicates that basic educational efforts on fungicide program design that adhere to resistance management principles should be targeted toward those who have been in the industry for fewer than five years, and those who classify themselves as laborers (who do not make on-farm decisions), because both groups felt less competent at this task than the national average (Figure 4). Targeting these groups will provide educational backgrounds for individuals who will continue on in the industry (i.e., those with five or fewer years of experience), and for those who are typically involved in the final stage of fungicide program delivery (i.e., laborers) who might be better able to identify a mistake before a product is applied to the vineyard.

Additional demographic targets for educational efforts could be owners (e.g., no on-site management activities), and those who own or manage fewer than 50 acres because both groups ranked lower in their fungicide spray program design competency (Figure 4). Although it is likely that owners in this study may not make on-site management decisions, they probably provide general direction for their operations. If owners had a better understanding of how fungicide resistance affects their operation (both socially and economically), it could result in a trickle-down effect of policies or procedures that emphasize resistance mitigation practices. Finally, over 48% of our respondents nationwide were from smaller vineyard operations (fewer than 50 acres; Table 5), which have different production constraints than larger operations. This survey indicates there would be value in developing educational material targeted specifically to each group as opposed to the current “one size fits all approach.” Many regional educational programs probably design materials targeting their regional demographics, for example, California and the Northwest focusing on materials for larger operations (Table 5). If smaller operations are accessing these resources, they may not find them appropriate for their operation. Specific to the winegrape industry, developing national materials that specifically focus on the challenges faced by smaller operations could have significant national reach. This could also improve consistent national messaging that would reinforce key resistance mitigation strategies across multiple resource venues, which is an important consideration for managing across-region pest management challenges (Wyenandt and Maxwell 2011).

Across all demographics, university extension services were the single most common source of information for fungicide efficacy and use (34%; Figure 8), as well as fungicide stewardship (38%; Figure 9) information. This was foreseeable, as the U.S. agricultural community tends to classify university extension services as a resource they can access for unbiased information and support for interpretation of research findings (Franz et al. 2010). However, the role of industry members’ peer network, and interactions with consultants should not be ignored. Combined, peers and consultants constitute 35% of the information sources on fungicide use and efficacy, and 38% for fungicide stewardship. This provides an opportunity for extension personnel to capitalize on the strength of the informal colleague network as a community-based learning tool to promote practice adoption among industry member groups (Prell et al. 2009, Franz et al. 2010, Rustagi et al. 2010, Hoffman et al. 2015). Developing and improving approaches to combine these two major forms of information delivery would help ensure that messaging on key concepts remains consistent across various industry outlets (Franz et al. 2010). One way to combine these activities would be to increase industry members’ participation in extension demonstration practices, as “seeing is believing” (Leach et al. 2019). In more traditional educational settings, this could be done through hands-on group work at educational events to support peer problem solving or using recently acquired knowledge to “case-study” scenarios designed to emphasize key concepts and provide a practical context. By focusing on how an individual learns, and what is of practical use for their operation, educators can also increase engagement with adult learners in the farming community (Franz et al. 2010, Hoffman et al. 2015).

An additional opportunity to enhance education and engagement could be a focus on increasing the number of licensed or certified professionals in the industry. Nationally, 27% of respondents indicated they did not possess a formal certification or license that is typically associated with pest management (Table 5). This lack of licensing or certification was common in vineyard owners (Supplemental Figure 3) and vineyard laborers (Supplemental Figure 4), whereas vineyard managers (Supplemental Figure 1) and viticulturists or crop consultants (Supplemental Figure 2) held these certifications and also felt more competent in spray program design. Generally most licenses or certifications in pest management require continuing education credits and are often managed by durably structured state or professional organizations. Encouraging industry members to seek out a license or certification program that is appropriate for their region may directly help them improve practices on their farm (e.g., vineyard managers, vineyard owners), expand their businesses in the case of viticulturists or crop consultants, or improve their employment options (e.g., vineyard laborers), and would also become a consistent forum to deliver educational materials on fungicide resistance management.

There are always challenges associated with interpreting survey data because of sampling and response biases. To maximize our response rate (n = 252) and minimize sampling bias, the survey was distributed through multiple methods and across multiple states. The multiple modes of delivery allowed for better tailoring of delivery style to meet local needs and considered state and/or regional differences in industry scale. Extension and industry winter (or off-season) meetings and workshops are one of the best ways to reach a large number of specialty crop stakeholders in a short period of time. However, these types of activities are typically attended by those in decision-making roles, or by those who need continuing education credits for licensing, which can introduce sampling bias. In an attempt to reduce the effect of sampling bias, we reached out to under-represented stakeholders, including crop consultants (outside of the western region), laborers, and fungicide representatives via social media, personal communication, regional newsletters, and industry listservs. While in the end, most respondents were vineyard managers and viticulturists or crop consultants who have some form of licensing credentials rather than vineyard owners or laborers, the former demographics were also the respondents defined as those making key management decisions in their operations. Arguably, this emphasizes the need to target educational programs to those respondents who were less likely to respond to the survey (i.e., laborers and owners) in an effort to increase knowledge and adoption of fungicide stewardship.