On Spread of Plant Disease: A Theory on Foci

The effects of initial inoculum levels on spatio-temporal development in black rot of cabbage from artificial sources, one per plot, were evaluated in replicated field experiments. The results support the hypothesis that black rot is a polycyclic disease. Its development was inoculum-dependent because the progress rate of epidemics and spatial spread were both positively correlated with the strength of the source. Fast disease development was related to the number of rain days. The spread of black rot, associated with the primary gradient, at first resulted from allo-infection, later followed by a phase during which allo-infection was complemented by auto-infection. Three-dimensional maps of disease severity showed the dominance of the primary focus. Maximum distance of black rot symptoms from the source of the focus was limited to a few metres so that damage to cabbage by focal inoculum was limited to the plants close to the source. Spatio-temporal development and initial inoculum were related. High inoculum levels in point sources resulted in faster outward spread of black rot, and differences between low and high levels were generally significant. Under the conditions of the experiments, performed during three relatively dry seasons, a single source of infection measuring 0·5 × 0·5 m was not capable of spreading disease over all the plants in a plot of 6·5 × 6·5 m. The results imply that severe disease where whole crops are infected, as observed regularly in The Netherlands, can only originate from a large number of small foci per field.

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“…The appearance of typical foci (Zadoks & Van den Bosch, 1994) around the inoculum sources supports this conclusion.…”

Section: Discussionsupporting

confidence: 71%

Spatio‐temporal development of black rot (X. campestris pv. campestris) in cabbage in relation to initial inoculum levels in field plots in The Netherlands

1999

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“…Zero-order epidemics, also known as focal epidemics, are amenable to modeling with deterministic partial differential and integral equations, and have received an impres-sive amount of careful analytical and experimental attention (Minogue and Fry, 1983a,b;van den Bosch et al, 1988a,b,c;Aylor and Ferrandino, 1989;van den Bosch 1990;Zadoks and van den Bosch, 1994;Assefa et al, 1995. At the other extreme, vagaries of climate, wind, and other exogenous forces determine the dynamics of second-order epidemics or pandemics (Campbell and Madden, 1990, Chap. 10).…”

Section: Introductionmentioning

confidence: 99%

Analytic Models for the Patchy Spread of Plant Disease

Bolker

1999

Bulletin of Mathematical Biology

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Plant epidemiologists have long been concerned with the patchy nature of plant disease epidemics. This paper presents a new analytical model for patchy plant epidemics (and patchy dynamics in general), using a second-order approximation to capture the spatial dynamics in terms of the densities and spatial covariances of healthy and infected hosts. Using these spatial moment equations helps us to explain the dynamic growth of patchiness during the early phase of the epidemic, and how the patchiness feeds back on the growth rate of the epidemic. Both underlying heterogeneity in the host spatial arrangement and dynamically generated heterogeneity in the spatial arrangement of infected plants initially accelerate but later decelerate the epidemic.

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“…No relevant information is available. In 1845 the blight spread over Europe as a first order 'focal epidemic' (Heesterbeek and Zadoks 1987;Zadoks and van den Bosch 1994), wonderfully illustrated by Bourke (1964) on the basis of hundreds of original documents. Bourke and Lamb (1993) analysed the seasonal weather for 1845.…”

Section: Potato Diseasesmentioning

confidence: 99%

The Potato Murrain on the European Continent and the Revolutions of 1848

Zadoks

2008

Potato Res.

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The tale of the Irish Famine, 1845-1849, following the outbreak of potato late blight, has been told repeatedly, but the parallel story of the Continental Famine, 1845-1847, has not yet been recorded. The Continental Famine was caused by poor harvests of potatoes, due to the same late blight, but also of grain, due to frost, drought, rust, voles, inopportune rains, floods and hailstorms. The Continental Famine was enhanced by hoarding, speculation, and poor governance. Hunger was followed by infectious diseases. The demographic effects of hunger and diseases are difficult to disentangle. The number of excess deaths due to the Continental Famine cannot yet be determined with any precision, but clearly it approaches that of the Irish Famine. The harvest failures of 1845 and 1846 and the resulting famines came on top of rural pauperisation and urban discontent, and thus contributed to the revolutions of 1848 on the European Continent. The statement 'an epidemic of potato late blight caused an epidemic of revolutions' is, perhaps, exaggerated but it contains a grain of truth.

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On Spread of Plant Disease: A Theory on Foci

Cited by 36 publications

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Spatio‐temporal development of black rot (X. campestris pv. campestris) in cabbage in relation to initial inoculum levels in field plots in The Netherlands

Spatio‐temporal development of black rot (X. campestris pv. campestris) in cabbage in relation to initial inoculum levels in field plots in The Netherlands

Analytic Models for the Patchy Spread of Plant Disease

The Potato Murrain on the European Continent and the Revolutions of 1848

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