Risk‐based management of invading plant disease

Abstract

Summary Effective control of plant disease remains a key challenge. Eradication attempts often involve removal of host plants within a certain radius of detection, targeting asymptomatic infection. Here we develop and test potentially more effective, epidemiologically motivated, control strategies, using a mathematical model previously fitted to the spread of citrus canker in Florida.We test risk‐based control, which preferentially removes hosts expected to cause a high number of infections in the remaining host population. Removals then depend on past patterns of pathogen spread and host removal, which might be nontransparent to affected stakeholders. This motivates a variable radius strategy, which approximates risk‐based control via removal radii that vary by location, but which are fixed in advance of any epidemic.Risk‐based control outperforms variable radius control, which in turn outperforms constant radius removal. This result is robust to changes in disease spread parameters and initial patterns of susceptible host plants. However, efficiency degrades if epidemiological parameters are incorrectly characterised.Risk‐based control including additional epidemiology can be used to improve disease management, but it requires good prior knowledge for optimal performance. This focuses attention on gaining maximal information from past epidemics, on understanding model transferability between locations and on adaptive management strategies that change over time.

Grower and regulator conflict in management of the citrus disease Huanglongbing in Brazil: A modelling study

“…(). The failure of culling around infected trees to control citrus canker means that it is unlikely that a culling strategy would be used in Brazil, although this type of control can potentially be successful for plant disease (Cunniffe, Cobb, Meentemeyer, Rizzo, & Gilligan, ; Hyatt‐Twynam et al., ; Parnell, Gottwald, Gilligan, Cunniffe, & van den Bosch, ; Parnell, Gottwald, van den Bosch, & Gilligan, ; Thompson, Cobb, Gilligan, & Cunniffe, ). Gottwald et al.…”

When prevention fails. Towards more efficient strategies for plant disease eradication

“…In their article, Hyatt‐Twynam et al . obtained the lowest number of removed trees with a risk‐based eradication strategy, but indicated that the complexity of this strategy might make it less transparent to stakeholders. By contrast, a variable control radius strategy could be easier for stakeholders to accept.…”

“…By contrast, a variable control radius strategy could be easier for stakeholders to accept. As Hyatt‐Twynam et al . point out, stakeholder acceptability merits careful attention when designing eradication strategies. Historically, eradication programs have been controversial, generating strong public opposition that has delayed or even halted interventions.…”

“…Hyatt‐Twynam et al . evaluate their simulation models using the citrus canker disease as a case‐study, which is actually one of the most significant examples of plant‐disease eradication. In South Africa, the disease was found on 33 farms and on 24 of them, entire orchards, or blocks of affected trees, were destroyed, amounting to 44 735 lost trees after the onset of the eradication campaign in 1918.…”

“…In fact, increased trade in commodities has been associated with more frequent biological invasions in recent decades (Hulme, ). In this issue of New Phytologist , Hyatt‐Twynam et al . (pp. 1317–1329) compare strategies for the eradication of emerging plant disease epidemics.…”