Activity of Trichoderma in the nursery for the control of Petri disease

Studies have recently demonstrated that Phaeomoniella chlamydospora and Phaeoacremonium species are able to produce latent infections in cuttings at nursery level and in causing Petri disease. In these last years studies were carried out for the development of procedures and products to prevent and/or reduce the infection in the nursery. In this study, greenhouse and nursery trials were carried out in order to evaluate effects of applications of Trichoderma harzianum (Rootshield ®) towards host-plant morpho-physiological characteristics and Pa. chlamydospora artificially inoculated on potted cuttings, as well as evaluating long-distance activity against Botrytis cinerea. In the nursery, thousands cuttings "Trebbiano" grafted on various rootstock (K5BB, SO4, 1103P, 420A) were treated in callusing boxes, and/or post callusing, at the bottom end, prior to planting. In this case Trichoderma treatment was repeated 30 days after planting. Treated cuttings were also potted and the trunk inoculated with a Pa. chlamydospora micelial plug, assessing the development of the necrosis 5 months from the inoculation. Moreover, leaves collected from cuttings were inoculated by dropping on the above leaf surface a conidial Botrytis cinerea suspension. The percentage of the infected area was evaluated. The study gave different outcomes depending on the Trichoderma stage of application and, to a lesser extent, the scion/rootstock combination. Post callusing treatments appeared to be the most effective providing an increase of quantitative-qualitative characteristics of root system, a slight but not significant reduction in necrosis development of inoculated cuttings, a higher percentage of excellent vines and a statistically lower necrotic area caused by B. cinerea. In the meantime, an increase of losses (5 - 15%) at the end of the growth season in the nursery was also assessed. Callusing-box application and treatments combination gave controversial results. On the whole, the application of Trichoderma at appropriate stage of the production of propagation material leads to a correct interaction with the host plant physiology, with positive effects on vegetative conditions, in terms of increasing of tolerance to stress-related diseases, like certain esca-related diseases.