He was consecrated to his office by Pope Paschal II himself during a synod in Benevento lasting from October to November 1108.
He was a reformer and he directed his energies towards restructuring his ancient diocese, which corresponded roughly to the Principality of Benevento, which was technically papal property.
Discord, however, reached such a level between the two Landulfs that the constable was forced to flee to Montefusco and the archbishop went to Rome in 1114 to seek mediation.
The pope responded by sending a Romuald, cardinal-deacon of Santa Maria in Via Lata, and Peter, cardinal-bishop of Porto, to arbitrate between the disputants.
Romuald found the archbishop to blame for the conflict with Greca and the pope deposed him from his see at the Council of Ceprano in October that year.