14.6 Cercospora (Ascomycota)

14.6 Cercospora (Ascomycota)

Many species of this genus cause plant diseases, mostly of the ‘leaf spot’ variety. Leaf spots are rounded blemishes occurring on the leaves of the infected plants; a typical spot has a defined edge with a darker border and a central zone varying from yellow to brown. Numerous spots can merge together and the larger areas can be called blights or blotch diseases.

Cercospora is not the only cause of leaf spot diseases but it causes disease on: alfalfa, asparagus, banana, brassicas, Cannabis, carrot, celery, cereals, coffee, cucumber, figs, geraniums, grapes, grasses, hazel, hops, lentil, lettuce, mango, millet, orchids, papaya, peanut, pear, peas, peppers, potato, roses, sorghum, soybean, spinach, strawberry, sugar beet, sugarcane (the spots merge into stripes; so the disease is called ‘black stripe’), sycamore, tobacco, watermelon, and many wild plants and ornamentals.

Cercospora beticola is the most destructive leaf disease of sugar beet worldwide; the disease reduces yield and quality of sugarbeet and the need to use fungicide to control leaf spot disease adds significantly to the cost of production. C. beticola overwinters as stromata in infected crop residues and spores produced on these are the prime source of infection of the leaves of the next season’s crop (Khan et al., 2008).

Disease control strategies rely on a combination of fungicide applications (alternating and combining fungicides differing in modes of action to avoid resistance development in the fungus), growing resistant cultivars, and appropriate crop rotation (to avoid the overwintering stromata).

Improvement of these integrated pest management systems is the main hope, now, for more effective and environmentally sound disease control. Plant varieties with greater genetic resistance is central to this, but pathogen-resistant strains often have lower yields in the absence of the disease, which is unacceptable in commercial practice. Promisingly, yield performance of recently isolated sugar beet varieties with resistance to Cercospora beticola have equalled yields of susceptible varieties and should allow reduced fungicide to be use in integrated pest management programmes (Skaracis et al., 2010; Vogel et al., 2018).

Resources Box 14.1

Where to find more information about crop diseases, crop losses, plant pathogens and food and agriculture statistics

We have a page giving references to scientific papers and hyperlinks to online resources.

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Updated July, 2018