Trichoderma's plant growth stimulating effect is well-recognized besides its well-known role as a biocontrol agent against plant diseases. Two greenhouse and field studies were conducted at the Papua New Guinea University of Technology (PNGUOT) to test the effects of Trichoderma harzianum on the growth of tomato and bean plants. Greenhouse potted plants were inoculated with three T. harzianum strains at 106 CFUmL-1, whereas, the field experiments were inoculated with T. harzianum strain LIPIMCO548 in rice bran at 0, 25, 50 and 75g/m2 soil. In the greenhouse experiments, Trichoderma inoculation increased the root and shoot length, and total fresh weight of bean plant up to 16.57, 20.79 and 21.37%, respectively over the un-inoculated control. For tomato plants, significantly higher (p ≤0.05, LSD) average root growth was observed when inoculated with T. harzianum strain CE262 over the control. On average, Trichoderma inoculation increased the root and shoot length, and the fresh weight up to 26.4, 9.6 and 18.8%, respectively over the control. Similar growth patterns were also observed in the field experiments. These results will be of immense value to vegetable growers in Papua New Guinea (PNG), especially to the intensive vegetable growing areas in the highland regions of the country.

Experiments were conducted in the laboratory, greenhouse, and field at the Papua New Guinea University of Technology (PNGUT) to assess the efficacy of Trichoderma harzianum against Rhizoctonia solani and Fusarium oxysporum. The dual culture of T. harzianum with R. solani and F. oxysporum isolated from the diseased bean and tomato plants under laboratory conditions showed 60.1% and 63.3%, and 54.9% and 61.6% growth reduction for R. solani and F. oxysporum, respectively. In greenhouse fungal inoculation experiments, bean and tomato plants showed relative germination index ranging from 0.56 to 1, 0.83 to 1, and disease reduction ranging from 64.8 to 96.1, and 20.3 to 83.7%, respectively. Field experiments involved tests with T. harzianum against one pathogenic fungus or against a combination of both R. solani and F. oxysporum, applied simultaneously as the pathogenic fungi or five days before application of pathogenic fungi. The results for bean and tomato plants showed relative germination index ranging from 0.42 to 0.94, and 0.63 to 0.94, and disease reduction recorded at 63.8 to 96.1%, and 11.3 to 63.9%, respectively. The outcomes of this study will form the basis for further investigation into the potential routine use of Trichoderma spp. as biological control agents against soil-borne pathogens in PNG.