Scott, © T he American Phytopathological Society.įungi and FLOs can be beneficial as well as pathogenic. Cedar-apple rust symptoms on the top and bottom of an apple leaf. Jones, © The American Phytopathological Society.įigure 3. Fruit rot caused by the pathogen Rhizoctonia, which also can cause damping off, root rot, and stem cankers. Some fungi and FLOs are able to live on only one host species, while others develop on many different kinds.įigure 2. Examples include Phytophthora and Botrytis species. Facultative saprophytes-usually survive as a parasite but have the ability to live on dead and decaying organic matter under the right conditions. Examples include Pythium species and many bacterial pathogens.Ĥ.
Facultative parasites-usually survive as a saprophyte but have the ability to parasitize and cause disease under certain conditions. All viruses, downy mildews, powdery mildews, rusts and smuts are obligate parasites.ģ. This is a very interesting group of pathogens in that they have a vested interest in prolonging the life of their host to increase their own viability. They cannot survive as saprophytes or be cultured in the laboratory. Can only grow as a parasite on or in a living host. These organisms can only survive or are obliged to gain nourishment by colonizing dead or decaying organic matter. Obligate saprophytes-always a saprophyte. Most of us have seen mycelium growing on old bread or rotten fruit or vegetables and may have referred to these organisms collectively as molds or mildew.įungi and FLOs (indeed all pathogens) can be grouped into the following four categories based on their preference for surviving on dead or decaying organic matter versus living tissue:ġ. Mycelia are the key diagnostic sign associated with diseases caused by fungi and FLOs. A collection of hyphae is referred to as mycelium (pl., mycelia). They obtain nutrients by absorption through tiny thread-like filaments called hyphae that branch in all directions throughout a substrate. Morphologyįungi and FLOs are eukaryotic organisms that lack chlorophyll and thus do not have the ability to photosynthesize their own food. These fungi can grow on corn and fill the seed with the toxin that not only attacks the liver, but is one of the most carcinogenic substances known. In 2006, dozens of dogs perished from food tainted with aflatoxin, a chemical produced by several Aspergillus species. In addition to being agents of preharvest and postharvest diseases and rots, fungi produce highly toxic, hallucinogenic and carcinogenic chemicals that not only affected the lives of millions historically, but continue to be problems today. In the United States alone, hundreds of millions of bushels of wheat have been lost in epidemic years to stem rust ( Puccinia graminis tritici). In the 1870s, an epidemic of downy mildew, caused by the fungus Plasmopara viticola, struck the grape vineyards of central Europe, causing great losses to grape growers and wine makers. The genus itself, Phytophthora, was named by Anton de Bary in 1876 as “plant destroyer.” This single organism caused the death of more than 1 million people by starvation and initiated one of the largest human migrations on the planet. The potato blight in Ireland and northern Europe, rampant during two successive seasons (1845–18–1847), was caused by the fungal-like organism Phytophthora infestans. Wheat crops of the Middle Ages were commonly destroyed when the grains became infected with a dark, dusty powder now known to be the spores of the fungus called bunt or stinking smut ( Tilletia spp.).
Some of the world’s great famines and human suffering can be blamed on plant disease-causing fungi and FLOs. The impact that fungi have with regards to plant health, food loss, and human nutrition is staggering. The importance of fungi as agents of plant and human disease, producers of industrial and pharmacological products, and decomposers has spurred scientists worldwide to study their biology. Bristow, © T he American Phytopathological Society. FLOs are organisms like Pythium and Phytophthora and those that cause downy mildew that until recently were considered fungi are now known to belong to a different taxonomic group.įigure 1.
#CROP BLIGHT DEFINITION HOW TO#
Plant pathology is the study of plant disease including the reasons why plants get sick and how to control or manage healthy plants.Ĭollectively, fungi and fungal-like organisms (FLOs) cause more plant diseases than any other group of plant pest with over 8,000 species shown to cause disease.
#CROP BLIGHT DEFINITION SERIES#
This is the seventh fact sheet in a series of ten designed to provide an overview of key concepts in plant pathology.
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