Читать книгу Plant Pathology and Plant Pathogens - John A. Lucas - Страница 26

The intensification of agriculture through plant breeding, widespread use of fertilizers, pesticides and plant growth regulators, with larger fields and shorter rotations, has brought in its wake new and sometimes severe disease problems. Changes in the types of crops grown, or in crop management practices, almost invariably lead to new challenges. Irrigation has opened up whole regions to agriculture, but the same water which brings life to the crop can also nourish and spread its microbial enemies. The extension of crops into new geographical areas has exposed them to novel disease agents; for instance, tropical plant species such as cocoa and cassava, which originated in South America, are grown extensively in Africa where they have succumbed to virus diseases spreading from native species. While breeding programs and chemical control measures have won notable victories in the campaign against plant disease, the situation is never static. If anything, in recent years the threat posed by pests and pathogens has increased, rather than decreased (Figure 1.10).

Figure 1.10 A convergence of forces increasing the threat of plant disease.

Source: Lucas (2017b).

The age we are living in has been described as the “Anthropocene,” as no part of the planet is now unaffected by human activity. Environmental change has taken place on a massive scale, altering ecosystems, modifying the distribution of species, and reducing biodiversity. The globalization of trade and travel has redistributed crops and plant products and inadvertently introduced their enemies into new regions. There is now conclusive evidence that the global climate is changing as a result of human actions. Altogether, the pace of such change is accelerating the adaptation and evolution of biological systems, including the pathogens causing animal and plant diseases. There is a need therefore for constant vigilance to ensure that the plants we grow remain healthy and productive.