Bactericidal and fungicidal effects of eight plant extracts on the growth of two honeybee pathogens,Bacillus larvae(causative agent of American foulbrood) andAscosphaera apis(causative agent of chalkbrood), andBacillus alvei(a secondary invader in European foulbrood), were evaluated. Cinnamon oil completely inhibited the growth ofB. larvaeat 10 ppm for 72 h. Camphor and citronellal inhibited all growth at 100 ppm for 72 h. Bay oil, clove oil, origanum oil, and thymol inhibited all growth at 1,000 ppm for 72 h, and α-terpinene inhibited all growth at 10,000 ppm for 72 h. Cinnamon oil completely inhibited the growth of A.apisat 100 ppm for 168 h. Bay oil, citronellal, clove oil, origanum oil and thymol inhibited all growth at 1,000 ppm for 168 h. Camphor inhibited all growth at 10,000 ppm for 168 h, and α-terpinene inhibited all growth for 72 h at 10,000 ppm. Cinnamon oil and thymol completely inhibited the growth ofB. alveiat 10 ppm for 72 h. Bay oil, camphor and origanum oil inhibited all growth at 100 ppm for 72 h. Clove oil and citronellal inhibited all growth at 1,000 ppm for 72 h, and α-terpinene inhibited growth at 10,000 ppm for 72 h. Several compounds reduced growth in a dose dependent manner at levels below their threshold values. These results suggest that plant extracts might play a significant role in the management of honeybee diseases.