The performance of a graphite and silica nanoparticles-based delivery system for T. harzianum in controlling the in vitro growth of R. solani and damping-off disease on tomato plants. The in vitro and in vivo experiments were arranged in the randomized complete block design. The in vitro treatment was a dual culture of R. solani and T. harzianum in the various components of formulation on PDA, i.e., T. harzianum + 5 wt.% graphite, T. harzianum + 1wt.% silica NPs., T. harzianum + 5 wt.% graphite + 1 wt.% silica nanoparticles, T. harzianum, 5 wt.% graphite, 1 wt.% silica nanoparticles, fungicide (mancozeb), and a control. The in vivo treatment included the application of T. harzianum in the same compositions as the in vitro treatment, except that there were two controls i.e., inoculated and noninoculated tomato plants with R. solani. T. harzianum by soaking tomato seeds in the formulation suspensions before planting. The results showed that all formulation compositions were able to inhibit the in vitro growth of R. solani. The inhibitions of the colony growth of R. solani caused by formulated and non-formulated T. Harzianum were the same. This proved that graphite and silica NPs did not resist to the ability of T. Harzianum in controlling R. solani, indicated that the formulation was promising to develop. However, the inhibition of damping-off disease incidence on tomato plants caused by formulated T. harzianum was the same as the non-formulated one only on day 7 after treatments. On days 14, 21, and 28, the inhibitions were lower than the non-formulated ones. It was suggested to reapply the formulation of
T. harzianum in the soil at planting and several days after.
