Which of the following is a method to manage root and stalk rots of sorghum?

Managing crop residues is an effective method for controlling root and stalk rots of sorghum because it helps reduce the incidence of pathogens that contribute to these diseases. When crop residues, particularly from previously infected plants, are left on the field, they can harbor and promote pathogens that affect subsequent crops. By incorporating or removing these residues, farmers can minimize the chance of disease transmission and reduce the overall pathogen load in the soil.

Additionally, proper management of crop residues can enhance soil health and promote beneficial microorganisms, further supporting healthy plant growth. This method not only targets the immediate concern of root and stalk rots but also contributes to an overall more sustainable and resilient agricultural system.

In contrast, the other options would not provide the same benefit and may even exacerbate disease conditions. Choosing plants with weak stalk strength, for instance, would likely lead to increased susceptibility to mechanical damage and disease. Over-applying fertilizers could lead to excessive plant growth that may weaken stalks and root systems, while planting at excessively high populations can increase competition for resources and create a more favorable environment for disease development. These practices can inadvertently increase the risk of root and stalk rots rather than manage them effectively.