‘Hass’ avocado, Persea americana Miller, fruit being imported into California from Mexico are infested with high levels of a previously unknown species of armored scale insect (Hemiptera: Diaspididae). This species has recently been described and given the name Abgrallaspis aguacatae Evans, Watson & Miller. However, the validity of morphological characters used to diagnose genera within the tribe Aspidiotini (Diaspididae) is the subject of continued debate. Here, we seek to circumnavigate the inherent problems associated with interpretation of somewhat plastic phenotypic characters. We use two different nuclear gene regions (28S and Elongation Factor 1α) and three different analysis methods (maximum parsimony, maximum likelihood, and Bayesian analyses) to infer phylogeny from DNA sequence data for 35 aspidiotine species. Our analyses suggest that the new species is misplaced in the genus Abgrallaspis Balachowsky and that this genus and several closely allied genera are paraphyletic or polyphyletic. The findings of our analyses are discussed specifically in relation to the current placement of A. aguacatae and more broadly in relation to the long-recognized problem of defining generic boundaries between Abgrallaspis, Diaspidiotus Berlese, and Hemiberlesia Cockerell.