The effect of Dipel 2 X, caffeine and sumithion 3% 0,60 days af­ter treatment on infestation of potato tubers with Phthorimaea opercu­lella was studied. Treatments with the afore-mentioned materials at con­centrations of 0.1, 0.2 and 0.3% decreased infestation. At 0.3%, the percentage of infestation on tubers dropped to approximately 10% for caffeine treatment, while treatment with Dipel 2X or sumithion resulted in zero infestation compared to 100% infestation in the control after 60 days. Treatments decreased the numbers of tunnel exits on infested tu­bers after 60 days to 0, 0 and 2 with 0.3% Dipel 2X, sumithion and caf­feine compared to 226.67 tunnel exits/1 kg. of tubers in the control.