Certified Arborist Practice Test

Microscopic worms that sometimes feed on trees and may carry diseases are known as nematodes. These are a diverse group of roundworms and can be found in various environments, including soil, freshwater, and marine ecosystems. Nematodes are particularly significant in the context of plant health because some species are phytoparasitic, meaning they can damage plant roots and other tissues directly. Additionally, certain nematodes are known to transmit plant diseases by acting as vectors for pathogens.

The other options do not accurately describe these microscopic organisms that impact trees. Protozoa are single-celled eukaryotic organisms, primarily known for their role in the soil ecosystem but not specifically associated with feeding on trees in the same way nematodes do. Fungi are a separate category of organisms and, while they can affect trees, they are not worms and generally do not fit the description. Viruses are pathogens that can infect plants but are not specified as microscopic worms; they are instead particles that require a host to replicate. Therefore, the definition and characteristics of nematodes align correctly with the context of the question regarding their relationship with trees.