Revealing The Answers

4 proactive strategies for managing elusive Fusarium fungus

Since the first observation of its destructive path on soybeans in 1917, the fungal pathogen Fusarium has plagued crops, silently causing stunted growth, root rot and seedling disease. To battle the pesky pathogen, farmers and researchers have taken to the fields, digging for answers hidden under the cover of soil.

The effects of this opportunistic pathogen have been difficult to quantify because symptoms often resemble those of other disorders. However, the roots of an infected seedling will have a dark discoloration of brown or red and an underdeveloped root system. Compared with healthy soybeans, infected plants often appear drastically smaller and underdeveloped and may even die before emerging from the seed.

“If we pull out an affected plant from the soybean field and look at the roots closely, we see some brown discoloration, but it is hard to tell if it is exclusive to Fusarium or a mix of pathogens on the root,” says Febina M. Mathew, Ph.D., assistant professor and field crops pathologist at South Dakota State University. “The base of the tap root will also be discolored with secondary roots undeveloped.”

Mathew is conducting research that she hopes will help farmers identify the pathogen. In a recent webcast from the Plant Management Network, Fusarium Species in Soybean Root Disease, she offered the following preemptive strategies for managing Fusarium, especially if problems with the disease have been seen in the past:

• Plant varieties resistant/tolerant to SDS and SCN – Fusarium tends to be an opportunistic pathogen, so stressors such as soybean cyst nematode (SCN) and sudden death syndrome (SDS) can increase root-rot issues and aggravate the disease.
• Plant in well-drained soil – Cool temperatures and wet soil favor the fungus.
• Use fungicide seed treatment – Treating seeds can help soybeans emerge early in the season and prevent damping off that pathogens can cause when conditions are favorable.
• Reduce crop residue when planting – Fusarium live for long periods of time and can survive in plant residues of no-tilled fields.

Fusarium’s elusive nature has made it a difficult pathogen to study, yet its ability to cripple a crop continues to be felt in most of the United States as well as abroad. In 2014, it is estimated that farmers lost 4.2 million bushels of yield to Fusarium root rot. Fusarium can survive for long periods of time within the soil, waiting for preferred conditions. It may not show symptoms on plants until it has a suitable environment to spread throughout a crop. These opportunistic tendencies further increase the difficulty of identification, putting even more importance on prevention and proactive soil management.