Abstract

Bioassay of five Trichoderma strains isolated from Cocoa ecological zones of Nigeria was carried out at Cocoa Research Institute of Nigeria. In the in vitroassessment the pathogen and antagonists were paired on potato dextrose agar (PDA) contained in 90 mm Petri dishes, while the effect of antagonists on the mycelial growth of the pathogen was determined for 120 h. The percentage disease incidence of the pathogen in the presence of the antagonists was determined using cocoa pod husk pieces (CPHP) and the early infection index of the pathogen was calculated over 8 days. All the Trichoderma strains screened inhibited the growth of the pathogen exhibiting between very strong (6) and strong antagonism (5) on an assessment scale of 0 to 6. The inhibition increased daily till the pathogen disappeared. The presence of Trichoderma strains reduced disease from 95.0% in the control to 25.0% the treatment that had highest incidence. The Early Infection Index (EII) was low in all the treatment in relation to the control.  The highest EII (16.03%) which was recorded in NIG-T293 treated samples was very low compared with the control (100%). The screened fungi are therefore potential bio-agents capable of controlling the disease on the field.

Key words: Bioassay, Trichoderma strains, disease incidence, biological control.