He was appointed head of the missions in northern Guatemala, but along with 80 other Jesuits fled the country in September 1871 when the Liberals gained control and persecuted the Catholic Church.

[2]: 118  In 1872 president Jose Maria Medina invited him to Spanish Honduras to found a college in the capital Comayagua.

Di Pietro became pastor in Corozal in the north of Belize until June 1876 when, weak from sickness, he was sent to Panama to recover his strength.

By October 1878 Pittar was having serious health problems and di Pietro returned to be Superior, remaining so until his death in 1898.

From his close association with Henry Fowler, the first Catholic colonial administrator (1877-1886), keeper of the government records and producer of the Honduras Almanack, di Pietro wrote accounts to acquaint his Superiors in England with Belize and to attract assistance of funds and manpower.

The Church in the northern districts was well-established and Bishop di Pietro was anxious about the education of the children there.

Then on 14 January 1893 the Roman authorities appointed di Pietro titular Bishop of Eurea and Vicar-Apostolic of British Honduras.

The mission which began in 1852 with no church, few Catholics, and 2 priests after 40 years numbered 20,000 Catholics among a population of 31,000 inhabitants, in 6 town churches – Belize Town, Corozal, Orange Walk, Stann Creek, Punta Gorda, and El Cayo – and 39 outstation chapels.