Which of the following is classified as a biotic (pathogen) causal agent?

Bacteria are classified as biotic causal agents because they are living microorganisms that can cause disease in plants. Biotic factors include all living organisms that can influence the health and growth of plants, such as pathogens like bacteria, fungi, and viruses. These agents interact with host plants and can lead to various symptoms, including wilting, leaf spots, and stunted growth.

Understanding the role of bacteria as pathogens is critical for effective plant management and disease control. By identifying bacterial infections, growers can implement appropriate strategies, such as selecting resistant plant varieties, practicing crop rotation, or applying targeted biological or chemical treatments to mitigate the impact of these pathogens.

In contrast, nutrient deficiencies and temperature extremes are classified as abiotic factors, as they stem from non-living environmental conditions that affect plant health. Pesticides, while they may control biotic agents, are synthetic or naturally occurring substances used to kill, repel, or manage pests and pathogens, rather than being pathogens themselves.