Brown Stem Rot in Soybeans: Symptoms, Causes, and Effective Control Strategies

One of the least anticipated diseases in soybean farming is brown stem rot which is a disease that has worked against one even before it can cause any obvious effects. The problems detected by many farmers come very late in the season when yield potential is already impaired. The disease silently kills the plant by attacking the vascular tissues, limiting water and nutrient transportation, and eventually making the plant weaker. When external symptoms set in, a lot of internal damage already has taken place.

This is even more difficult as brown stem rot in soybeans is often confused with other diseases resulting in delayed or wrong decisions in its management. This misdiagnosis helps to add to the growing concern of growers in particular in areas experiencing recurring outbreaks. Internal nature of the disease is also a limitation as farmers seeking remedies usually resort to treatments such as fungicide for stem rot​. Thus, it is important to realize the significance of timely detection and implementation of a comprehensive brown stem rot treatment to protect the crop output and provide long-term health of crops.

What causes brown stem rot in soybeans?

To manage brown stem rot of soybean, it is necessary to have an understanding of what causes this condition. Cadophora gregata, a soil-borne fungus causes the disease, and survives in the affected crop (residual) in the field. This pathogen attacks the roots of a soybean at the beginning of the growing season and slowly expands to the vascular system of the plant.

The environmental conditions contribute greatly to the development of the disease. Low temperatures and wet soils provide a perfect condition in which fungi will grow and cause infections. Soybean monocropping areas are especially susceptible because they can be cultivated continuously to enable the bacteria count to accumulate.

Studies conducted by the Crop Protection Network and other University Extension organizations are revealing that the fungus lives inside the crop remains and is spread conducively in cool wet climates. Crop rotation is an important management strategy due to this. Brown stem rot of soybeans may be a chronic problem that requires proper intervention because as years go by, soybean productivity declines over time.

Early Detection of Brown Stem Rot Soybeans Symptoms

In soybean production, interests should be on early detection of brown stem rot soybean symptoms to reduce rate of losses in terms of yield. Interveinal chlorosis is one of the initial observations, as the tissue between the veins is yellowish, with the veins being green. This yellowing can progress into necrosis (as the disease advances), and cause leaves to brown and dry out.

But the best diagnostic characteristic is located within the plant. A brown stain plainly showing infection can be seen through the opening of the stem. This is an internal symptom that enables the distinction between brown stem rot and other diseases such as sudden death syndrome that may exhibit same symptoms of that leaf but their internal symptom is different.

Premature leaf fall and decreased vigor that have been in infected plants have a direct effect on yield. Since the disease manifests itself later in the season, farmers need to be careful and observe crops frequently to be able to detect brown stem rot in soybeans and before it establishes the widespread outbreak.

Development of the disease and the cycle of infection

The disease process of brown stem rot starts a lot earlier than many farmers may think. The fungus attacks the soybean roots at the initial stages of the vegetative period but often manifests in the reproductive period, especially stage 3-5. This latency renders the disease very tricky and hard to control.

The pathogen infects a plant plant leading to obstruction of flow of water and nutrients through penetration into a plant vascular tissue. This interference weakening of the plant itself reduces the growth and yield potential of the plant. Residues of crops in the field are the main source of infection, which helps in the disease to survive through growing seasons.

The infection occurs internally meaning that losses are likely to be experienced before one observes any symptoms. This underscores the need of what causes brown stem rot in soybeans and adopting preventive programs as opposed to only dealing with reacting programs.

Traditional practices of Brown Stem Rot Treatment

Conventional methods of treatment of brown stem rot are based on cultural and preventive treatment principles, particularly, the use of non-chemical control. The most effective method to decrease the amount of pathogen in the soil is crop rotation of non-host crops like corn. Planting of resistant soybean varieties is also an important step that will help reduce the effects of the disease.

Sanitation in the fields such as proper management of the residue will help eliminate the decrease in the survival of the fungus between seasons. Nevertheless, a lot of farmers continue to use chemical solutions, trying to find an effective fungicide for stem rot. Regrettably, the pathogen is located in the vascular system of the plant and, therefore, in most cases, the drugs do not have a great effect.

This has resulted in a growing desire to have convergent solutions that integrate both culture and biological solutions. To learn how to treat stem rot properly, it is essential to go beyond the traditional approaches and consider implementing approaches that would help treat the disease at its origin.

How Integrated Management Reduced Brown Stem Rot Impact

How to treat stem rot? One of the soybean farms in the Midwestern United States had regular losses in yield because of brown stem rot in soybeans. The farmer, in the beginning, was over dependent on fungicides that were considered organic and perceived them to be the most effective brown stem rot treatment of the disease. But outcomes were imperfect, with the infection still progressing within the company.

The farmer used integrated management approach after seeking advice of agronomy experts. These comprised crop rotation, application of resistant varieties, addition of biological treatment using Bacillus subtilis and Bacillus velezensis. These positive microbes were beneficial in enhancing the health of roots and also formed a protective layer against the pathogen.

The outcome was noteworthy in two successive growing seasons. Incidences of disease declined significantly, plant vitality enhanced and yield recovery went up by 1520 percent. In this case, the significance of using a combination of several strategies and not using a single solution can be noted. It also shows how stem rot can be effectively treated using balanced and sustainable approach.

These observations are supported by research carried out by the field tests conducted in universities, which indicated that Bacillus-based solutions serve to improve disease suppression through competition with pathogens and also activation of plant defense mechanisms.

Biological Control Bacillus-based Solutions

Biological control has proven to be a potent tool in brown stem rot treatment. Good microorganisms like Bacillus subtilis, Bacillus velezensis can provide an answer to chemical treatments. These microorganisms act by the production of antifungal compounds, which prevent the growth of Cadophora gregata.

They also inhabit root zone forming a protective layer, which inhibits the formation of pathogens. Moreover, these microbes enhance the natural defense system of the plant and make it defensive against infection.

As opposed to traditional fungicide for stem rot which might not be effective in addressing internal infection, biological solutions attack the main source of the issue. They are the necessary part of the modern soybean agricultural practice due to its compatibility with integrated disease management systems. Now you know how to treat stem rot is not a rocket science. 

Integrated Control Strategy for Sustainable Soybean Farming

Brown stem rot can only be addressed through an integrated approach in the long run. To control the disease, farmers should use a combination of crop rotation, resistant varieties, and biological treatment to be effectively controlled. The pathogen survivability may also be minimized by enhancing the soil health through the management of fungicide for stem rot and microbes.

Frequent monitoring of the field is required with a view of detecting symptoms and quick brown stem rot treatment. Through knowing the disease life cycle and adopting preventive strategies, farmers will be in pivotal position to save a huge amount of yield loss.

Sustainable practices are also beneficial in controlling brown stem rot in soybeans as well as enhancing the productivity of the farms. An effective approach grounded in combining cultural, biological, and monitoring activities can guarantee the same result in disease suppression and the success of agriculture in the long term.

Reference:

• De Jensen, C. Estevez, J. A. Percich, and P. H. Graham. "Integrated management strategies of bean root rot with Bacillus subtilis and Rhizobium in Minnesota." Field Crops Research 74.2-3 (2002): 107-115.
• Abd-El-Khair, H., and H. I. Seif El-Nasr. "Applications of Bacillus subtilis and Trichoderma spp. for controlling the potato brown rot in field." Archives of Phytopathology and Plant Protection 45.1 (2012): 1-15.