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Fusarium Root Rot

CROPS IMPACTED: Soybeans, pulses, tomatoes

Fusarium Root Rot

Family: Nectriaceae

Fusarium Root Rot Fusarium Root Rot

About Fusarium Root Rot

Life Cycle

These fungi have the ability to live for a number of years in the soil or plant debris as a resting spore. The fungi can also live in the soil in greenhouses, but not for nearly as long as in this situation it rests as a different type of spore called conidia. Fusarium root rot will infect crops where there has been a history of bean growth, and is commonly seen in the middle of, or late in the growing season. When host plants are stressed, this disease can cause a significant loss in yield. Fusarium has the ability to spread through irrigation lines and is commonly transmitted during transplanting, especially since this often causes wounds to the roots which make an easy entrance for the fungus. Fusarium has also been known to overwinter on rockwool slabs and can transfer to other plants that come into contact with it. While many spores can be found on an infected plant’s stem, they are not commonly dispersed in the air due to its moist composition; transmission through water is much more common.

Fusarium Root Rot Identification and Habitat

Identification

It is often hard to diagnose this disease as it is sometimes present at the same time as other soil borne fungi. However, typically when a plant is infected with Fusarium root rot, the taproot (usually the lower portion) and the lateral roots of the plant will rot, turning black or brown. Usually you can see the outer layers of the root beginning to decay and it may also show vascular discoloration. When lateral roots die off, new roots sometimes develop slightly above them on the part of the taproot which has not yet been infected. In severe cases fusarium root rot can cause foliar symptoms such as yellowing, stunting, and defoliation; in these cases, this disease is also referred to as fusarium wilt.

Varieties

Main types to affect soybeans:

  • • Fusarium solani
  • • Fusarium oxysporum

Habitat

Fusarium root rot is soil borne and is present in many areas throughout the United States where soybeans are produced. It is caused by the fungi Fusarium, but symptoms of Phthium, Rhizotonia and other pathogens that infect soybeans are often diagnosed as Fusarium root rot. These fungi can survive in the soil for long periods of time, making it hard to treat. Infection is likely to occur early in the spring when weather conditions are wet and cool, often within the first 4 weeks of growth. However, soybean plants are also vulnerable later in the season if the soil is dry and the plants become stressed. There is evidence that areas affected by flooding also have a greater infection rate of this disease. Soil pH, crop rotation, soil compaction, and soil type can all affect the level of severity of root rot. The disease will not develop if temperatures exceed 90 degrees Fahrenheit.

Fusarium Root Rot Management and Control Methods

Cultural Control

Try to prevent a favorable Fusarium environment which includes keeping soil well-drained and avoiding soil compaction as much as possible. Limiting host plant stress whenever possible from other pathogens can also reduce root rot as the plant will have increased vigor and can withstand the fungi more easily. Practice crop rotation to decrease the soil’s pathogen level, especially avoid close rotation of dry beans as they are most susceptible. When conditions are not favorable for germination, ridging soil near the plants base can assist with root growth and deter major root rot damage. Check fields early in the growing season for dead seedlings. If any are found, remove them from the field to reduce the chance of spread. Always use seed that is good quality.

Chemical Control

A fungicide treatment plan is often necessary when dealing with fields that have a history of Fusarium root rot. Fungicide seed treatments can assist with the plants germination process but is ineffective once the plant becomes an adult.

Alternative Fusarium Root Rot Names

  • • Fusarium wilt
  • • Root rot

Sources

http://www.extension.umn.edu/agriculture/crop-diseases/soybean/fusarium.html

https://www.ndsu.edu/pubweb/~bernelso/soydiseases/fusarium.shtml

http://www.omafra.gov.on.ca/english/crops/facts/01-081.htm