Use of bark mulch pre-inoculated with Trichoderma atroviride to control Armillaria root rot

Bark mulch is commonly used to control weeds and preserve soil fertility. Coniferous barks can host Armillaria spp. and the use of infected bark by growers can lead to the spread of Armillaria root rot in orchards. Several species and strains of Trichoderma genus are antagonists of plant-pathogenic fungi. This study demonstrates that barks pre-inoculated with Trichoderma atroviride SC1 can provide effective control of Armillaria root rot. Experiments to evaluate the survival of T. atroviride SC1 on bark of different species and the efficacy of Trichoderma-treated bark on Armillaria gallica in vitro and on strawberry plants were carried out. T. atroviride SC1 can persist and grow on the different types of bark (larch, pine, fir and a mixture of these species) for a long period after the treatment (up to 16 weeks). The highest survival of T. atroviride SC1 was achieved on the bark mixture. Armillaria root rot was significantly lower on strawberry plants that were mulched with bark pre-inoculated with T. atroviride SC1 than that observed on the untreated control (25 and 70%, respectively). Introducing biocontrol agents and promoting their establishment through bark mulch carrier could represent an alternative or complementary strategy for the control of this disease.