Tylenchus tritici vs nematode

Tylenchus tritici and nematode both are nouns.

Word	Noun	Adjective	Verb	Adverb
Tylenchus tritici	Yes	No	No	No
nematode	Yes	No	No	No

As nouns, nematode is a hypernym of Tylenchus tritici; that is, nematode is a word with a broader meaning than Tylenchus tritici:

Tylenchus tritici: small roundworm parasitic on wheat
nematode: unsegmented worms with elongated rounded body pointed at both ends; mostly free-living but some are parasitic

Other hypernyms of Tylenchus tritici include nematode worm, roundworm.

Tylenchus tritici (noun)	nematode (noun)
small roundworm parasitic on wheat	unsegmented worms with elongated rounded body pointed at both ends; mostly free-living but some are parasitic