Root rot is a disease affecting cotton crops that is caused by the fungal pathogen Rhizoctonia bataticola. Root rot is a soil-borne disease that attacks crop roots, causing substantial damage and death. It is widespread in moist or damp soil and can affect crops and Cotton. Slow growth, wilting leaves, early leaf loss, and branch dieback are all root rot symptoms. If the disease is not treated, it will spread and finally destroy the tree. It is critical to handle root rot as soon as possible since it can spread fast and cause severe harm.
Root Rot Disease Management in Cotton
The Causal Organism of Root Rot Disease
Root rot in Cotton is caused by the fungal pathogen Rhizoctonia bataticola (Pycnidial stage: Macrophomina phaseolina). The hyphae of this fungus are septate and reasonably thick and produce irregular, black sclerotia measuring 100 microns in diameter. These sclerotia are a key diagnostic feature for identifying the disease in affected cotton plants. The disease is particularly problematic for cotton growers, as it can lead to significant crop losses if left untreated.
Disease Cycle of Root Rot Disease
Cotton root rot disease has a soil-borne cycle in which the pathogen can survive as sclerotia in the soil for several years. The principal propagation mechanism is sclerotia dispersion, which can be transported by irrigation water, farm machinery, and other agricultural processes. When sclerotia come into touch with fresh cotton plants, they can infect the roots and spread the disease, resulting in considerable crop losses if not appropriately controlled. Understanding the disease cycle is essential for creating appropriate management methods to reduce the impact of the illness on cotton crops.
Favorable Conditions for the Spread of Root Rot Disease
- Certain environmental conditions can exacerbate the spread of dry root rot in cotton crops. Heavy rainfall followed by dry weather can create ideal conditions for the pathogen to thrive.
- High soil temperatures of 35-39°C, the cultivation of crops that are favorable hosts for the pathogen (such as vegetables, oilseeds, and legumes), and wounds caused by ash weevil grubs and nematodes.
- These factors can create an environment conducive for the pathogen to thrive and infect cotton plants, leading to crop losses.
Symptoms of Root Rot Disease in Cotton
- Root rot in cotton plants is characterized by sudden wilting of the plants, which are often scattered throughout the field.
- Affected plants appear straw-colored; in some cases, the lower leaves and stems may be brown.
- The topmost petioles and leaflets droop, and the lower portion of the tap root remains in the soil when the plant is uprooted.
- The tap root is dark, decaying, lacking lateral and fine roots, and brittle with shredded bark.
- Dark, minute sclerotial bodies can be noticed on exposed roots or inside the stem’s base. When the collar region’s dry stem is broken vertically, mycelium or sclerotia can be detected in the pith.