What is the method used to determine the presence or distribution of nematodes?

• A. Soil and root tissue sampling
• B. Visual inspection of leaves
• C. DNA sequencing in the field
• D. Air sampling

Answer: (A)

Nematodes are primarily detected by sampling where they live: soil and root tissue. They spend most of their life in the soil around the plant roots and, often, inside the roots themselves. So collecting soil from the root zone and sampling root tissue lets you directly observe or extract nematodes, assess how many are present, and determine which areas of a field are infested. This approach provides a real measure of presence and distribution across the environment.

Visual inspection of leaves isn’t reliable because nematodes are subterranean and don’t always produce clear above-ground symptoms, especially in early stages. DNA sequencing in the field isn’t practical for routine detection, since it requires lab processing, specialized equipment, and time. Air sampling isn’t effective for nematodes because they reside in soil and within roots, not suspended in the air in detectable quantities.