Exploring the potential of Trichoderma secondary metabolites against Tetranychus urticae (Acari: Tetranychidae)

This study aimed to determine 1) the effects of fungal filtrates containing secondary metabolites from five different isolates of four different Trichoderma species (Trichoderma afroharzianum, T. guizhouense, T. harzianum, and T. virens) grown in different liquid media [malt extract broth (MEB), potato dextrose broth (PDB), yeast peptone glucose (YPG), minimal medium (MM), czapek-dox broth (CDB)] on Tetranychus urticae female, and 2) the effects of Trichoderma filtrates obtained from YPG liquid media on the different biological stages of T. urticae in Petri dish and pot experiments. Results showed that the Trichoderma filtrates produced in the YPG medium exhibited the highest mortality rate of 67.6-83.1 % against T. urticae females at 7 days post-application (dpa) compared to other media. In Petri dish experiments, the mortality rates of Trichoderma filtrates on egg, larva, protonymph and deutonymph stages of T. urticae at 7 dpa were 54.0-57.8 %, 71.5-76.0 %, 72.5-79.8 % and 72.8-80.8 %, respectively. Significant differences were observed between the Trichoderma species and control (P < 0.01) but not among the Trichoderma species (P > 0.05). Trichoderma afroharzianum (83 %) and T. virens (84 %) showed the highest mortality rate on T. urticae adult females at 7 dpa and statistically significant differences were observed among Trichoderma species. Pot experiments revealed that the number of viable T. urticae eggs and mobile stages was significantly lower for T. afroharzianum (110.3 eggs, 105.8 mobile stages) and T. virens (118.5 eggs, 115.3 mobile stages) compared to the control (518.9 eggs, 452.5 mobile stages) at 7 dpa. Significant differences were observed between Trichoderma species and control, but not between T. afroharzianum and T. virens. These findings suggest that Trichoderma secondary metabolites are highly effective against economically important pest such as T. urticae, demonstrating their potential as bio-acaricides. Future research should focus on identifying the specific acaricidal compound(s) within these filtrates.