Evaluation of Trichoderma harzianum strain T22 as biological control agent of Calonectria pauciramosa

The objective of this research was toevaluate Trichoderma harzianum strain T22 as abiocontrol agent of collar and root rot caused bydifferent Calonectria pauciramosa isolates. Thus, themicrosclerotia-forming ability and virulence of twentyC. pauciramosa isolates were assessed. Microsclerotiaproduction varied partially among the isolates anddual culture with T22 on carnation leaf agar revealedisolates with both high and low microsclerotia-formingability. Inoculation tests on red clover (Trifloliumpratense) demonstrated its susceptibility to the pathogen.On red clover, the degree of virulence and T22effects in controlling infections were highly variableamong the isolates tested. A nursery trial performed onFeijoa sellowiana seedlings confirmed previousresults, clearly indicating virulence variability amongC. pauciramosa isolates. For three isolates tested innursery trial, T22 effectiveness in controlling infectionwas inversely related to their degree of virulence.Overall, T. harzianum strain T22 showed good antagonistactivity in reducing microsclerotia production oncarnation leaf and the incidence and severity of collar and root rot on both selected hosts. This data could becrucial in developing integrated pest managementstrategies in ornamental plant nurseries.