![]() During late summer to early fall, the fungus will produce a survival structure called a sclerotium either on or inside the tissues of a host plant. The lifecycle of Sclerotinia sclerotiorum can be described as monocyclic, as there are no secondary inoculums produced. For size reference, a dime is also included. The apothecia in this photo are circular, tan, and have a white lining near the edge of the structure. Life cycle This image captures a cluster of apothecia from a downward angle, so that only the tops are visible. For soybeans specifically, optimal conditions include canopy temperatures less than 28 ☌ and plant surface wetness for 12–16 h on a daily basis or continuous surface wetness for 42–72 h. sclerotiorum prefers darker, shadier conditions as opposed to direct exposure to sunlight. sclerotiorum will produce an abundance of mycelium and sclerotia. Optimal temperatures for growth range from 15 to 21 degrees Celsius. sclerotiorum is capable of completely invading a plant host, colonizing nearly all of the plant's tissues with mycelium. The pathogenic fungus Sclerotinia sclerotiorum proliferates in moist and cool environments. For soybeans, crop yields are inversely correlated with the incidence of Sclerotinia stem rot an estimated of 0.25 metric ton per ha is lost for each 10% increment of diseased plants. ![]() Compared to 23 common soybean diseases, sclerotinia stem rot was the second most problematic disease in the United States from 1996 to 2009. During particularly bad years, these soybean yield reductions caused producers to loose millions of dollars. An analysis of soybean yields from 1996 to 2009 in the United States found that sclerotinia stem rot reduced yields by over ten million bushels in half of the studied growing seasons. Sclerotinia stem rot (or 'white stem rot', ) causes large yield losses in temperate climates, especially during cool and moist growing seasons. Some crops it affects commonly are soybeans, green beans, sunflowers, canola, and peanuts. It can also spread in a storage facility throughout the harvested crop. White mold can spread quickly in the field from plant to plant. It affects young seedlings, mature plants, and fruit in the field or in storage. The fungus can survive on infected tissues, in the soil, and on living plants. Its diverse host range and ability to infect plants at any stage of growth makes white mold a very serious disease. White mold affects a wide range of hosts and causes sclerotinia stem rot. This can occur when the fruit is in the field or when in storage. Next, white fungal mycelium covers the fruit and it decays. On fruits, the initial dark lesions occur on the tissue that comes in contact with the soil. These can include chlorosis, wilting, leaf drop, and death quickly follows. Once the xylem is affected, other symptoms occur higher up in the plant. The mycelium then cover this necrotic area. Usually this is preceded by pale to dark brown lesions on the stem at the soil line. One of the first symptoms noticed is an obvious area of white, fluffy mycelial growth. It can usually be found on tissues with high water content and in close proximity to the soil. White mold can affect their hosts at any stage of growth, including seedlings, mature plants, and harvested products. ![]() It can also affect woody ornamentals occasionally, usually on juvenile tissue. Sunflowers are common hosts for white mold. Common hosts of white mold are herbaceous, succulent plants, particularly flowers and vegetables. Economically significant hosts include Vicia faba, for which Lithourgidis et al have done extensive work over the years. sclerotiorum is among the most omnivorous of plant pathogens and so would not make a good mycoherbicide. Hosts and symptoms Sclerotia from sunflower sclerotiorum is onset in the field by favorable environmental conditions, losses can be great and control measures should be considered. This pathogen can occur on many continents and has a wide host range of plants. These sclerotia give rise to a fruiting body in the spring that produces spores in a sac which is why fungi in this class are called sac fungi (Ascomycota). A key characteristic of this pathogen is its ability to produce black resting structures known as sclerotia and white fuzzy growths of mycelium on the plant it infects. ![]() sclerotiorum can also be known as cottony rot, watery soft rot, stem rot, drop, crown rot and blossom blight. Sclerotinia sclerotiorum is a plant pathogenic fungus and can cause a disease called white mold if conditions are conducive.
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