Root rot caused by Pythium aphanidermatum is one of diseases of olive trees. Three synthetic chemical compounds were tested to assess their inhibitory effect on Pythium aphanidermatum Ethyl 5-amino-7-((3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate (7), Ethyl 5-amino-7-((3-hydroxy-5-methyl-1H-pyrazol-4-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate(8) and Ethyl 5-amino-7-((5-amino-2,7-dihydroxypyrazolo[1,5-a]pyrimidin-3-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate(9) were synthesis to study their effect on mycelium growth, zoospore and oospore production of P. aphanidermatum isolated from young olive trees cultivated in Ain Seleen, Fayoum governorate, Egypt. Ethyl 5-amino-7-((3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate (7), showed high efficiency as growth inhibition of fungal mycelia, followed by (pyrazolopyrimidine 9, and then pyrazolopyridine 8 at 10 mg/ L. Ethyl 5-amino-7-((3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate (7), showed its ability to decline the production of zoo-spores and oospores of the fungus at concentration 300 mg/L, compared to other chemicals of Ethyl 5-amino-7-((5-amino-2,7-dihydroxypyrazolo[1,5-a]pyrimidin-3-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate(9), Ethyl 5-amino-7-((3-hydroxy-5-methyl-1H-pyrazol-4-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate(8). Rate of inhibition in all treatments reached more than 85% in case of the use of Ethyl 5-amino-7-((3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate (7). This study offers data for the use of Ethyl 5-amino-7-((3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)-3,4,8,8a-tetrahydro-2H-pyrano[2,3-b]pyridine-6-carboxylate (7) in controlling fungal disease to olive feeder roots infected by P. aphanidermatum