Which of the following is an environmental factor in the plant disease pyramid?

• A. Temperature and humidity.
• B. Plant color.
• C. Soil type.
• D. Fertilizer type.

Answer: (A)

Environmental factors in the plant disease pyramid are the abiotic conditions that influence pathogen activity and disease development. Temperature and humidity are classic examples because they determine how well a pathogen can grow, germinate, and infect, as well as how long leaves stay wet enough for infection to occur. When the right combination of warmth and moisture occurs on a susceptible plant, disease pressure rises and epidemics are more likely.

Plant color is a trait of the host, not an environmental condition. Soil type can affect moisture availability and root health, but it isn’t the typical environmental parameter used to forecast disease in the pyramid. Fertilizer type changes plant nutrition and vigor (host status) and is a management factor rather than an environmental condition.