Abstract:
Tomato (Lycopersicon esculentum Mill.) Is a crop of great economic importance, having as one of the main problems the plant parasitism by nematodes of the genus Meloidogyne, which are forming galls on the root. To control this disease, chemical method is the most widely used method. However, there are several problems associated with the use of synthetic chemicals. Biological control is favorable alternative for the management of root-knot nematodes, as it is economically sustainable and environmentally friendly. Thus, the objective of this study was to investigate the antagonist effects of Bacillus subtilis and Trichoderma harzianum and their times of application on root knot nematode disease of tomato and yield. Suspensions of T. harzianum, B. subtilis and their combinations at eight levels were used as biological control agents against root-knot nematode. Three incubation periods was arranged for laboratory experiments using completely randomized design. Three times of application (two weeks before, simultaneously and two weeks after nematode application) were arranged for greenhouse experiments using completely randomized block design. The highest egg hatching inhibition (65%) after 4days and J2 mortality (96.2%) after 96 hours were recorded in T. harzianum and B. subtilis combination, followed by T. harzianum and B. subtilis. The galling indices were reduced by all biocontrols with great effect when they were in combination than alone. Galls (25.32) and low egg mass number per root system (47.3) were recorded from the combinations of the biocontrols B. subtilis and T. harzianum. However, only the fungus T. harzianum enhanced plant growth and yield in all the treated pots without nematode. However, all bio-controls showed crop growth enhancement by reducing the disease indices compared to nematode inoculated control. The study revealed that the use of T. harzianium and B. subtilis can help for the management of root knot nematode under controlled conditions. However, further studies should be made to evaluate the effectiveness of the bio-controls and their combinations under field conditions
