Final answer:
Herbivores do not cause disease in plants; they are animals that feed on plants rather than infectious agents. Bacteria, viruses, and fungi are pathogens that can cause plant diseases.
Step-by-step explanation:
The organism that does not cause disease in plants is d. Herbivore. While bacteria, viruses, and fungi are all considered pathogens and can cause diseases in plants, herbivores are not classified as disease-causing agents. Instead, they are animals that feed on plants but do not infect them with diseases. Bacteria, viruses, and fungi, on the other hand, can invade and damage plant tissues as pathogens, causing a wide range of plant diseases. For example, viruses are simple microorganisms that can multiply only within living cells and require a susceptible host plant, the presence of a virulent pathogen, and the right environmental conditions to spread diseases like the late blight of potato.
Herbivores may damage the plant by consuming its parts, but they do not cause infectious diseases that can spread from plant to plant. Instead, they act directly and usually do not induce the same types of internal systemic effects within the plant that are characteristic of diseases caused by pathogens.