Trichoderma-formulated products alternated or not impact in Sclerotinia sclerotiorum management considering the origins: laboratory and field borne sclerotia

Abstract: White mold, caused by Sclerotinia sclerotiorum, has the sclerotia as initial inoculum. The sclerotium parasitism reduces the apothecium formation, ascospore release, and disease incidence. In this regard, Trichoderma-based products are deployed on large scale wherever this disease is important; but little is known about the contribution of alternating Trichoderma-based products on the sclerotia parasitism, disease incidence, and contribution to plant yield. Furthermore, little is known about the contribution of the sclerotia origin on the performance of the biocontrol agent. In the present work, Trichoderma-based products were sprayed solo and alternately at the V2 and V4 phenological stages to evaluate their effectiveness in controlling white mold in soybean. Two field trials were conducted in different locations. The evaluations were: yield-related variables, grain yield (kg/ha), and white mold-related variables (disease incidence, sclerotia parasitism, germination, and viability, and the number of apothecia) on sclerotia originated from the field and produced in laboratory. Regarding the disease parameters, all BCA treatments were different from the control regarding incidence of white mold, while germination of sclerotia was decreased with Trichoderma spray. The sclerotia origin (lab or field) affected its capability to produce apothecia and cause disease. The application of these BCAs regardless of the sequence they were applied reduced sclerotia viability, disease incidence and sustained higher yield.