Potential biological agents isolated from apple fail to control Glomerella leaf spot in the field

Glomerella leaf spot (GLS) has great impact on apple crops in Parana/Brazil because the majority of the orchards in the state are planted with the cultivar 'Gala', which is very susceptible to the disease. The objectives of this study were to evaluate several potential biological control agents as well as a commercial biocontrol product were applied to apple plants and compared with mancozeb for control of GLS on leaves and fruit. Test plots included an experiment station orchard as well as a commercial orchard. In the experimental orchard, treatments showed different effects between the three crop seasons. In the commercial orchard, the effects of the biological controls were not significantly different from control in the two areas evaluated. The commercial biocontrol product showed no effect on GLS in leaves and fruits. Leaf cover with cells of the antagonists visualized by scanning electron microscopy revealed flaws in the biofilm, enabling germination and appressoria formation by Colletotrichum. (C) 2015 Elsevier Inc. All rights reserved.