IN VITRO SCREENING OF MEDIA AND OTHER FACTORS ON BIOLOGICAL CONTROLOF COCOA BLACK POD FUNGUS (PHYTOPHTHORA PALMIVORA)

Abstract

Cocoa black pod pathogen (Phytophthora palmivora) cause an annual crop losses that may range from 30 - 90% in cocoa farms. Therefore, in vitro screening was undertaken to assess the effects of media and other factors on potential of four fungi (Paecilomyces sp., Trichoderma harzianum, Rhizopus stolonifer and Penicillium digitatum)as biological control agents against this pathogen. The test fungi were isolated from cocoa farm and the screening was done on M9 medium using dual culture techniques. The results showed that the six media tested enhanced antagonistic activities and could be good for the study of biological control. The percentage inhibition of pathogen growth observed in each medium was well above 60%. Temperature range for the antagonistic activities of the fungal isolates was between 15 35°C outside which the antagonistic activities dropped. The effect of pH range used was observed to be significantly (PCO.05) decreased with increase in pH Strong antagonism of the pathogen was observed between pH 5 - 6.5. The result from nutritional factors on antagonistic activities of the four fungal isolates revealed that the antagonistic effects were not significantly different (P<0.05) among the supplements used but was highest in pectin- and glucose- supplemented media suggesting that nitrogen and carbon sources were essential for successful production of inoculum biomass as well as for sustaining biological activities. The efficacy of these tested fungi under field conditions is further being investigated.