Influence of different application times of Trichoderma in the nursery for the reduction of wood pathogens and quality improvement of grafted cuttings.

Wood pathogens of grapevine are recognized to be already present in propagation material. These infections together with field infections through pruning wounds, which represent the main source of infection cause decline symptoms in the young vineyards. More recently, the availability of biological control products to be applied in the control of GTDs had a large increase. Application timing of a product based on Trichoderma atroviride SC1 (Vintec®) was tested for two years in a commercial nursery to establish the influence of application timing on the quality of the grafted vine and level of natural infections in the nursery. The formulation was applied at three stages: rehydration, callusing, basal callus formation followed by soil drenching. In addition, the effect of the combined applications was also tested. All treatments were compared with controls (another Trichoderma-based product, plants treated with synthetic fungicide and untreated plants). Surveys included assessment of plant quality and viability first, after callusing and later after a growth season in the nursery soil. At uprooting root development was analysed by video image analysis and quality assessed as percentage of certifiable plants. The final grafted vines, ready for sale, were used for isolating the mycoflora, thus analyzing the influence of application at different stages of the grafted cuttings production on the fungal mycoflora and in particular fungal colonization by wood pathogens. The rehydration stage showed to be the better performing application in reducing fungal infections, whereas the applications at the basal callus followed by soil drenching produced plants with a better root quality, and a different increase of the certifiable plants number depending on the rootstock tested. The use of biological control products requires a lot of care in detecting the most useful application timing, avoiding overlapping of needless treatments.