Chapter 23

Greenhouse Disease Management

Fungal Diseases of Greenhouse Plants

Fungi constitute the largest number of plant pathogens and are responsible for a range of serious plant diseases. Most greenhouse plant diseases are caused by fungi. They damage plants by killing cells and/or causing plant stress. Sources of fungal infections are infected seed, soil, crop debris, nearby crops, and weeds. Fungi are spread by wind and water splash, and through the movement of contaminated soil, animals, workers, machinery, tools, seedlings and other plant material. They enter plants through natural openings such as stomata and through wounds caused by pruning, harvesting, hail, insects, other diseases, and mechanical damage. Some of the fungi are responsible for foliar diseases—downy mildew and powdery mildew are some of the highly prevalent foliar diseases. Other fungi—clubroot, Pythium species, Fusarium species, Rhizoctonia species, and Sclerotinia species—are soilborne diseases. Some fungal diseases occur on a wide range of grenhouse plants. These diseases include anthracnose, Botrytis rots, downy mildew, Fusarium rots, powdery mildew, rusts, Rhizoctonia rots, and Sclerotinia rots. Others are specific to a particular crop group, e.g. clubroot (Plasmodiophora brassicae) in brassicas, leaf blight (Alternaria dauci) in carrots, and red root complex in beans.

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