Effect of Bacterial Antagonist on Phytopthora cactorum and Apple Crown Rot

Bacterial antagonist B8 produced an inhibition zone with each of four Phytophthora cactorum isolates on corn meal agar (CMA) plates. Infections with three P. cactorum isolates were significantly reduced when the soil was simultaneously inoculated with B8. Growth of P. cactorum was completely inhibited on CMA amended with 40–100 per cent 10 fold concentrated B8 extract. Percent oospore germination of P. cactorum was significantly reduced when B8 was present in suspension for 9, 12 and 15 days from inoculation. Survival of oospores was significantly reduced at 60 and 90 mm depths in soil. Bacterial antagonist B8 significantly reduced the population of viable P. cactorum oospores in the top 30 mm of soil where oospores generally survive.