The effect of cultivation on the size, shape, and persistence of disease patches in fields

Epidemics of soil-borne plant disease are characterized by patchiness because of restricted dispersal of inoculum. The density of inoculum within disease patches depends on a sequence comprising local amplification during the parasitic phase followed by dispersal of inoculum by cultivation during the intercrop period. The mechanisms that control size, shape, and persistence have received very little rigorous attention in epidemiological theory. Here we derive a model for dispersal of inoculum in soil by cultivation that takes account into the discrete stochastic nature of the system in time and space. Two parameters, probability of movement and mean dispersal distance, characterize lateral dispersal of inoculum by cultivation. The dispersal parameters are used in combination with the characteristic area and dimensions of host plants to identify criteria that control the shape and size of disease patches. We derive a critical value for the probability of movement for the formation of cross-shaped patches and show that this is independent of the amount of inoculum. We examine the interaction between local amplification of inoculum by parasitic activity and subsequent dilution by dispersal and identify criteria whereby asymptomatic patches may persist as inoculum falls below a threshold necessary for symptoms to appear in the subsequent crop. The model is motivated by the spread of rhizomania, an economically important soil-borne disease of sugar beet. However, the results have broad applicability to a very wide range of diseases that survive as discrete units of inoculum. The application of the model to patch dynamics of weed seeds and local introductions of genetically modified seeds is also discussed.

The cultivation of Castanea sativa (Mill.) in Europe, from its origin to its diffusion on a continental scale

The history of Castanea sativa (sweet chestnut) cultivation since medieval times has been well described on the basis of the very rich documentation available. Far fewer attempts have been made to give a historical synthesis of the events that led to the cultivation of sweet chestnut in much earlier times. In this article we attempt to reconstruct this part of the European history of chestnut cultivation and its early diffusion by use of different sources of information, such as pollen studies, archaeology, history and literature. Using this multidisciplinary approach, we have tried to identify the roles of the Greek and Roman civilizations in the dissemination of chestnut cultivation on a European scale. In particular, we show that use of the chestnut for food was not the primary driving force behind the introduction of the tree into Europe by the Romans. Apart from the Insubrian Region in the north of the Italian peninsula, no other centre of chestnut cultivation existed in Europe during the Roman period. The Romans may have introduced the idea of systematically cultivating and using chestnut. In certain cases they introduced the species itself; however no evidence of systematic planting of chestnut exists. The greatest interest in the management of chestnut for fruit production most probably developed after the Roman period and can be associated with the socio-economic structures of medieval times. It was then that self-sufficient cultures based on the cultivation of chestnut as a source of subsistence were formed.

El estudio del cultivo de roza = The study of shifting cultivation /

Includes indexes.

Report to the Jamaica chamber of commerce on the sugar duties question in England, as the same might affect the future cultivation of the British West India colonies.

"Memorial to the Honorable the Lords commissioners of Her Majesty's treasury": p. [17]-19.

Vocal method. A complete method for the formation and cultivation of the voice.

Mode of access: Internet.

Vegetables and their cultivation; the history, cultivation, and forcing of culinary vegetables, saladings, and herbs, for home use and exhibitions; also the formation of the vegetable garden; the management of soils; manures and their uses; and the eradication of injurious insect and fungoid pests, etc. ...

Mode of access: Internet.

Essentials of irrigation and cultivation of orchards /

Mode of access: Internet.

A complete manual for the cultivation of the strawberry; with a description of the best varieties. Also, notices of the raspberry, blackberry, currant, gooseberry, and grape; with directions for their cultivation, and the selection of the best varieties.

Mode of access: Internet.

The gardener's manual : containing plain instructions for the selection, preparation, and management of a kitchen garden : with practical directions for the cultivation and management of some of the most useful culinary vegetables /

Attributed to Charles F. Crosman. Cf. Richmond, M.L.H. Shaker literature.

Nominations of Ginger Ehn Lew to be General Counsel ... Lauri Fitz-Pegado to be Assistant Secretary and Director-General of the U.S. and Foreign Commercial Service of the Department of Commerce : hearing before the Committee on Commerce, Science, and Transportation, United States Senate, One Hundred Third Congress, second session, February 10, 1994.

Shipping list no.: 95-0098-P.