Erickson, whose Nashville-based Erickson Public Relations has handled the singer's press since 2007, apparently informed the Swift management team that she is resigning this month, said the Hollywood Reporter.
"Swift has her sights set on bringing all PR efforts in-house to the management company," a source said.
Erickson started handling Swift, 24, as the country star's debut album in 2006 was about to cross the million-sales mark and continued on through 2012's Red.
A new album is expected in late 2014.
During Erickson's tenure, Swift's high-profile TV bookings have included hosting duties on 'Saturday Night Live', and performances at the Grammys, the MTV Video Music Awards and many country awards shows.