Abstract: Field trials were conducted in Wicklow, New Brunswick, Canada to study the antibiosis ability of aerobic compost tea against foliar and tuber diseases of potatoes. For soil drenching, extracts were prepared using three types of compost organic material including thermal compost, static wood chips and vermi castings. Kelp, humates, rock dusts, grain and alfalfa meal, soluble plant sugar and liquefied fish were added during a 24 h compost tea aerobic brewing cycle. For foliar application, soluble plant sugar, a natural yucca surfactant and liquefied fish were added as food to the compost tea prior to foliar application. Six treatments were used: untreated control (C); drench compost tea (DCT); foliar food (FF); foliar compost tea (FCT); drench compost tea+foliar food (DCT+FF) and drench compost tea + foliar compost tea (DCT+FCT). Both soil drenching and foliar application of compost tea or food lead to a significant increase in the severity of foliar late blight (Phytophthora infestans). Compost tea treatments had significant effects on emergence, stems number, silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani). Foliar food applications increased the number of stems produced. The severity of silver scurf was the highest when drench compost tea treatment was used. In case of black scurf, the severity was the highest when a combination of both drench compost tea and foliar compost tea were applied. Treatments had no significant effect on dry rot (Fusarium sp.), common scab (Streptomyces scabiei), early blight (Alternaria solani), bacterial soft rot (Erwinia carotovora subsp. carotovora), yield, or size of tubers produced.