Four field experiments were carried out from 1998 to 1999 and from 1999 to 2000 growing seasons of potato to investigate the relationship between leafminers and Alternaria alternata. The experiments established differential susceptibility among potato varieties to alternaria leaf necrosis, relationship between leafminer infestation and the level of necrosis, use of insecticides to reduce leafminer and leaf necrosis damages, and use of poly-ester fleece to eliminate leafminer and eventually reduce leaf necrosis. Results of the study indicate that control of leafminer is of primary importance because this will automatically lead to control of the damage caused by A. alternata.