Root rot on bean plants can be detrimental not only to the plant but also to the entire crop. It is imperative to remove the infected plant and all surrounding soil to keep the disease from spreading. Prevention is vital to having healthy, bountiful produce and lush, full plants.
Fusarium is the most widespread type of root rot. It is generally caused by the roots of the plant being exposed to too much water for long periods of time. The infection spores rapidly develop in water and quickly attack the roots. Another cause is if the roots are exposed to a feast and famine watering system. This type of watering does not allow the plant to have a steady nutrient supply and may cause it to be weak and susceptible to all sorts of diseases.
Fusarium root rot is identified by deep red lesions of various sizes, which develop below ground on the stems and roots of the bean plant. The red lesions turn brown as the rot progresses, and the gaps expand in the cortical tissue of the affected plant. In major cases of root rot infection, all of the roots become diseased and eventually ruined. To identify this disease, scratch the surface of the infected area to reveal small red flakes.
Each strand of the Fusarium root rot infection has adapted to slightly different environments. Therefore, it is difficult to detect the temperature the disease favors; it can occur in soil that is anywhere from 60 to 90 degrees Fahrenheit. In general, root rot is severe in soggy soil because the fungi reproduce zoospores that can move the water and strike roots and stems. The fungus forms thick skins that are able to survive difficult environmental conditions. Many species can grow and thrive on decomposing organic materials. The infected plant material may move throughout the garden by irrigation, wind, water currents or farm animals, or by tilling the infected soil back into the dirt. Soil that contains the infection remains infested.
Managing and preventing the infections can be simple. Provide ideal growing environments by watering the plant regularly, fertilizing when needed and making sure the roots are not exposed to standing water. Although some types are more resistant than others, all bean varieties may become infected if precautions are not taken.
Control root rot by planting beans in a warm, thoroughly prepared, well-aerated and fertile soil. The quicker the seedling grows from a seed, the less the chance is that the plant will be attacked by root rot. Good drainage is especially vital because it reduces the movement of the swimming infection spores. Using seed treatments or applying fungicides containing an active metalaxyl helps to control the spread and development of the disease. Active ingredients are normally listed below the brand name on fungicide labels.