Plant Pathology and Plant Pathogens. John A. Lucas

Plant Pathology and Plant Pathogens - John A. Lucas


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in affected countries.

      A further consequence of disease is the impact of measures taken to control pathogens that threaten export markets. Attempts to eradicate the destructive cocoa swollen shoot virus (CSSV) from Ghana by means of statutory removal of infected and surrounding trees not only entailed the most costly eradication campaign ever attempted, but also lead to political unrest. In the USA and South America, spread of the bacterial disease citrus canker has only been contained by burning huge numbers of infected citrus trees and nursery stock, combined with vigilant quarantine measures. In Florida, this included removing asymptomatic citrus trees from private gardens within affected areas, which inevitably brought plant health authorities into conflict with home owners. Outbreaks of crop diseases can also impact on agricultural practices and policy. The major epidemic of southern corn leaf blight in the United States in 1970 (see Chapter 5, Figure 5.1) raised doubts about the wisdom of achieving genetic uniformity in modern cereal crops and forced a reassessment of the breeding methods employed in the production of new cultivars.

      Plant pathogens can also have major impacts on both natural and managed forests. Currently, sudden oak death is spreading in the western USA and Europe, while ash dieback has recently invaded the UK. With the expansion of international trade in plants and plant products, the frequency of invasions by exotic pests and pathogens is increasing, with serious implications for many native plant species (see Chapter 5).

      Quantifying Losses Due to Disease

      Source: Oerke (2006).

Crop Weeds Pests Pathogens Viruses Total
Wheat 7.7 7.9 10.2 2.4 28.2
Rice 10.2 15.1 10.8 1.4 37.4
Maize 10.5 9.6 8.5 2.7 31.2
Potatoes 8.3 10.9 14.5 6.6 40.3
Soybeans 7.5 8.8 8.9 1.2 26.3
Cotton 8.6 12.3 7.2 0.7 28.8
Stacked bar graph illustrating the comparison of proportions of total production of major food and cash crops lost with stacked vertical bars for weeds, pests, pathogens, and products.

      Source: Data from Eckert (1977).


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Librs.Net
Commodity Country of origin Potential loss (%)
Loss during low‐temperature storage Apples England, USA 2–50
Carrots England, USA 6–38