Exploring the combined use of biocontrol agents Trichoderma atroviride and Engytatus nicotianae against the tomato psyllid (Bactericera cockerelli)

Abstract

Control of tomato potato psyllid (TPP), Bactericera cockerelli, is problematic because of pesticide resistance and environmental issues. The predatory bug Engytatus nicotianae has proven to be an efficient biocontrol agent against TPP in glasshouse grown tomatoes. Trichoderma fungi offer numerous benefits to plants and soil, including biocontrol of pathogens, enhanced plant growth, increased nutrient uptake, and improved soil health. Therefore, there could be advantages to the combined use of Trichoderma and E. nicotianae. However, Trichoderma spp. have the potential to alter the behaviour of pests or their enemies by modifying plant defence metabolites such as volatile organic compounds (VOCs). This study investigated the individual and combined efficacy of Trichoderma atroviride and E. nicotianae in reducing TPP abundance across different developmental stages (eggs, nymphs, adults) and the number of infested leaves in glasshouse grown tomatoes. Plant VOC emissions were also investigated under the different treatments. Across all measured TPP stages all three treatments (E. nicotianae alone, T. atroviride alone, and T. atroviride + E. nicotianae) significantly reduced mean TPP counts relative to the control but there were no significant differences in VOC emissions among the treatments. Trichoderma atroviride alone was less effective than E. nicotianae alone or its combination with Trichoderma atroviride to suppress TPP populations. The combined use of T. atroviride + E. nicotianae did not show significant advantages over the use of E. nicotiana alone but did not appear to negatively affect the predatory bug’s performance. This suggests that the combined use of these biocontrol agents is feasible and can be considered in the light of other potential advantages of Trichoderma to the crop such as growth promotion and pathogen defence.