On large-seal farm trials, the effectiveness of Bacillus thuringien­sis (B.T.), Granulosis virus (C.V.) and the organophosphate compounds; Fenitrothion and Profenofos against P.operculelfa were studied at El­Gharbia, El-Monifia and El-Behera Governorates, in 1995 season. Results from field experiments indicated that Bacillus thuringiensis, G.V. and the chemical insecticides reduced the incidence of P.opercuiella on potato tubers. There was no significant difference between B.t., G.V. and profe­nofos in the percentage of PTM infestation, number of holes in potato tubers and rotten tubers. Using PTM sex pheromone traps would help in determining the suitable time for biological or chemical insecticides ap­plication. Also, the correlation between the environmental conditions such as temperature and R.H., and the population density of PTM should be taken into account. Under storage conditions, after 42 and 63 days of application, the percentage reduction in PTM infestation of potato tu­bers for the biological agents was higher than Fenitrothion. Although po­tato tuber moth larvae hide in the tunnels that they burrow in the leaves and tubers, B.thuringiensis and G.V. applications reduced their popula­tion levels considerably and reduced the percentage of infestation, num­ber of PTM larvae, and yield loss in potato tubers in comparison with that provided by Fenitrothion. No significant differences in the fficacy against the PTM between the application of stored tubers with one appli­cation of the tested compounds or two applications.