Biotic stress includes which of the following?

• A. Fungi, bacteria, mistletoes, viruses, intraspecific competition, weeds; biotic disease is transmittable from plant to plant.
• B. Abiotic factors such as drought and frost.
• C. Mechanical damage only.
• D. Nutrient deficiency only.

Answer: (A)

Biotic stress comes from living organisms that affect plants. The items listed—fungi, bacteria, viruses, mistletoes, and competition with other plants (intraspecific competition and weeds)—are all living agents that can cause disease, injury, or reduced growth by directly infecting the plant or by competing for light, water, and nutrients. In contrast, drought and frost are abiotic factors: non-living environmental conditions that stress plants. Mechanical damage is physical injury, not a living stressor, and nutrient deficiency is a chemical/nutritional problem, also not caused by living organisms. Because biotic stress involves living agents that can spread between plants, many biotic diseases are transmittable from plant to plant.