: Conventional streak method was employed to establish the percentage inhibition as well as
intercolony distance between the test organisms obtained from the infected substrate and mycelia of the mushroom
during substrate colonization. The test organisms are: a fungus, Kutilakesopsis macalpineae and a bacterium,
Pseudomonas tolaasii. The effect of pH and temperature on the mycelia growth of P. ostreatus was also investigated.
There was a gradual increase in the percentage inhibition from 33.3 % at 24 h to 75.0 % at 168 h for K. macalpineae
and 37.5 % at 24 h to 70.0 at 168 h for P. tolaasii. The inter-colony distance between the antagonists and the mushroom
mycelium gradually decreased. Optical density of the mycelium growth was at its optimum at pH 4.5 and temperature of
25 °C respectively. In vitro study also showed a significant increase in the optical density from 0.855±0.03 at 24 h to
1.316±0.02 at 168 h in the absence of test antagonist as against 0.812±0.06 and 0.79±0.02 at 24 h to 1.103±0.03 and
0.902±0.03 at 168 h when K. macalpineae and P.tolaasii were used as test antagonistic respectively.