Infection with luminescence bacteria in conjunction with fungal organism Fusarium sp. Is prevalent in larvae of mysis and post larvae of P. monodon in hatcheries. Histopathological studies revealed the presence of Fusarium sp. in hepatopancreas of infected larvae. Histolytic secretions of macroconidiophores of Fusarium sp. destroyed carapace which developed into dome like structure to accommodate the outer extension of Fusarium sp. Though Vibriosis sp. could be treated with antibiotics, Fusarium caused heavy mortalities