Biological control of Armillaria root rot

RemedierTenet (formerly called Remedier) is a biocontrol product that contains two very potent organisms, Trichoderma asperellum, Trichoderma gamsii, for the control of fungal diseases of agricultural crops. The product is registered in Europe and the company (Isagro USA) will soon register this product in the US. According to the company, the Trichoderma strains in Tenet colonize the rhizosphere and the soil where they compete for nutrients and space. Both organisms are capable of parasitizing other fungi, including Rhizoctonia, Sclerotinia, Verticillium and straminipiles, including Phytophthora and Pythium. The target use on the label includes the control of Oak root rot on fruit trees. The company recommends adding this product at planting and then following up with two applications per year, one in the spring and one in the summer. In a published paper (Cristinzio 2003) activity against oak root rot of peach was documented in Italy. Seven years after setting up the field experiment, the Remedier treated trees had 2 % disease incidence compared to 12% in the untreated control. However, the disease pressure (12%) did not seem to be high in this study and it is not known whether the product will hold up against Southeastern Oak root rot, which is caused by a different species of Armillaria. The importance of Oak root rot in the Southeast and the lack of management options warrant an investigation of this product for Oak root rot control in South Carolina. 

In order to investigate Remedier for ARR control of peach in South Carolian, two field experiments were established in 2007. In this study, Trichoderma asperellum and T. gamsii formulated as Remedier WP were drenched onto peach trees 3 to 12 days after planting (2007), and biannually thereafter in spring and fall for a total of three years in two commercial replant sites of South Carolina. All trees were planted in spots where a tree had declined from ARR the previous season to maximize disease pressure. Tree survival and trunk diameter were determined each year in the control and Remedier WP treatments. Four years after planting (2011), 50% of all control trees and Remedier WP-treated trees had died from ARR. There was no statistical significance in survival between the treatments in either location. However, three and four years after planting, surviving Remedier WP-treated trees had significantly larger tree trunks compared to control trees in the Campobello location. Not enough trees survived in the other location for meaningful analysis of tree trunk diameter data. Our results show that in soils with heavy ARR inoculum levels biannual drenches of Trichoderma formulated as Remedier WP starting at planting are ineffective for ARR control of peach. This manuscript is in press in the online journal Plant Health Progress, published by APS.