Above: A nematode seen under a microscope. UF/IFAS photo by Tyler Jones.
A parasite is an organism that lives on or inside of another organism, weakening its host but usually not killing it. This feature distinguishes it from a parasitoid, which typically does kill its host.
Words related to parasite include parasitic (adjective), parasitism (noun) and parasitize (verb). Obligate parasitism occurs when an organism can only survive by its parasitic relationships with another organism.
Plant-parasitic nematodes are one example of a parasitic bug. These nematodes are very small and may only be visible with a microscope. Like other nematodes, plant-parasitic nematodes live in the soil, where they feed on plants.
Many of these parasitic nematodes attack plants from the outside with a spear-like body part called a stylet. Because of this behavior we call them ectoparasites, parasites that live on the outside of their host.
Other nematodes live inside a plant, making them endoparasites. Root-knot nematodes are a well-known endoparasite that cause a plant’s roots to swell and resemble knots.
When plant-parasitic nematodes attack, they make it harder for plants to absorb water and nutrients, and may cause yellowing or stunting. Plant-parasitic nematodes attack turf, landscape plants and crops.
However, not all nematodes are bad news. In fact, many nematodes are beneficial to plants and may even be used in biological control. For example, nematodes have been instrumental in controlling mole crickets, a damaging pest in pastures and golf courses.
Learn more about nematodes at http://edis.ifas.ufl.edu/topic_nematode_management.