We assessed the infestation of Bactrocera invadens Drew Tsuruta & White on field-collected Cavendish dwarf bananas of different ripening stages in Kenya and Mozambique. Of 5085 fruits collected in Kenya, B. invadens was reared from all ripening stages except bananas at the mature green stage. The highest level of fruit fly infestation was recorded from the ‘all yellow’ fruit ripening stage at 17% of which 401 B. invadens was recovered. In Mozambique, no fruit flies were recovered from a total of 169 fruits of different ripening stages sampled. Of 1349 culled Cavendish dwarf bananas sample, the highest number of fruit flies (518 B. invadens) was recovered from fruits that were precociously ripened. In field cage experiments conducted in Kenya and Mozambique, although oviposition wounds (101–587) were observed on green bananas after artificial infestation with 100–1000 gravid B. invadens females, no flies were recovered from fruits at the green stage of harvest maturity. Based on the results of these findings, mature green bananas of the Cavendish dwarf cultivar should be considered as a non-host stage of maturity for B. invadens. However, bunches with precociously ripened fingers and with other damages such as cracks and splits, ant burns, abrasions, point bruise, tip rot or general decay should be carefully inspected before export and discarded because such damages can permit attack by B. invadens and pose the risk of inadvertent translocation of the insect during export.