A field survey was carried out to investigate the presence of mangrove borers at the mouth of San Pablo River in the Gulf of Montijo, western Pacific of Panamá. Previous reports of the National Environment Authority (ANAM) indicate a high degree of root tip atrophy and breakage in young plants of red mangrove, Rhizophora mangle. Samples of roots were sawed off and examined for isopod burrow openings. Analysis revealed the presence of the eastern Pacific root-boring Sphaeroma peruvianum Richardson. The organism bore the roots and it is the likely cause of fall trees due to the lack of root support. A voucher specimen was deposited in the Smithsonian National Museum of Natural History, Washington, DC (USNM 1139603).