Rhizobius is a genus in the fungi kingdom (see Disease resistance in fruit and vegetables), as well as an obsolete name for the aphid genus Pemphigus.

Rhyzobius is a genus in the lady beetle family (Coccinellidae). It belongs to tribe Coccidulini of subfamily Coccidulinae, which is sometimes subsumed in the Coccinellinae as a tribe with the Coccidulini downranked to subtribe.

The genus was established by J.F. Stephens in 1832. Often misspelled as "Rhizobius", that is actually an older name, now suppressed, for a genus of woolly aphids. The misspelling was first made in the original description in 1832; however, Stephens had used the name in 1829 already (as nomen nudum) and written it "Rhyzobius", so this spelling is used now. Louis Agassiz in 1846 argued that Stephens intended to write "Rhizobius" all along and formally proposed to change the name thus, but this is considered unwarranted.

Species of Rhyzobius can be found almost anywhere on Earth. Rhyzobius lophanthae is used for biological pest control in Australia, namely scale insects (Coccoidea).

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