Perceived Vulnerability and Propensity to Adopt Best Management Practices for Huanglongbing Disease of Citrus in California

Abstract

Huanglongbing (HLB) disease of citrus, associated with the bacterium “Candidatus Liberibacter asiaticus”, is confined to residential properties in Southern California eight years after it was first detected in the state. To prevent the spread of HLB to commercial citrus groves, growers have been asked to adopt a portfolio of voluntary best management practices. This study evaluates the citrus industry’s propensity to adopt these practices using surveys and a novel multivariate ordinal regression model. We estimate the impact on adoption of perceived vulnerability to HLB, intentions to stay informed and communicate about the disease and various socio-economic factors, and reveal what practices are most likely to be jointly adopted as an integrated approach to HLB. Survey participants were in favor of scouting and surveying for HLB symptoms, but they were reluctant to test trees, use early detection technologies (EDTs) or install barriers around citrus groves. Most practices were perceived as complementary, particularly visual inspections and some combinations of preventive practices with tests and EDTs. Participants who felt more vulnerable to HLB had a higher propensity to adopt several practices, as well as those who intended to stay informed and communicate with the coordinators of the HLB control program, although this effect was modulated by the perceived vulnerability to HLB. Communication with neighbors and the size of citrus operations also influenced practice adoption. Based on these results, we provide recommendations for outreach about HLB management in California and suggest future directions for research about the adoption of plant disease management practices.

How growers make decisions impacts plant disease control

“…first, this has been used previously in plant epidemiological literature ( [12], [13] and [17]). Secondly, and most importantly, we believe this comparison to be most similar to what real growers might be expected to do ( [18], [53], [20]). It requires a moderate amount of information, as it only relies on the individual knowing their own profit from the previous season and the expected profit of the alternative strategy (Table 2).…”

“…We now continue our investigation using only the "grower vs. alternative" model set-up. The idea of the "reflexive producer" means that growers are likely to respond to previous season's outcomes ( [18]), but still incorporate information about what the likely infection risk is for the next season ( [53], [20]). We therefore believe that this is a useful approximation of how growers may actually perceive profitability, though we include analysis of the other models in Appendix 4 Figure 3.…”

How growers make decisions impacts plant disease control

“…We now continue our investigation using only the “grower vs. alternative” model set-up. The idea of the “reflexive producer” means that growers are likely to respond to previous season’s outcomes [ 18 ], but still incorporate information about what the likely infection risk is for the next season [ 20 , 53 ]. We therefore believe that this is a useful approximation of how growers may actually perceive profitability, though we include analysis of the other models in Fig C in S4 Text .…”

“…This is similar to the hypothetical scenarios we previously outlined, particularly that of the “grower vs. alternative” scenario where a grower is using a particular control strategy and is then approached by an extension worker that proposes an different strategy. Thus, motivations and considerations of a grower to partake in specific control schemes are highly varied and depend on the market demands, information network available to growers, disease pressure and proximity to previous outbreaks [ 20 ].…”

Tolerant crops increase growers’ yields but promote selfishness: how the epidemiology of disease resistant and tolerant varieties affect grower behaviour

“…In our behavioural model, we assumed that all growers would have access to the same information regarding disease pressure and the expected profits. In reality, a grower’s knowledge of these quantities will be highly dependent on their communication network (Milne et al (2016)), their trust in expert knowledge (Sherman & Gent (2014)), their experience with previous outbreaks (Garcia-Figuera et al (2021)) etc .. How growers react to differences in profit (represented by our parameter η ) will also vary between individual growers, and will impact long-term outcomes (Murray-Watson et al (2022)). Growers must balance these information sources with market demands to make their decisions regarding disease control, and become what Kaup terms the “reflexive producer” (Kaup (2008)).…”