Eduardo Donoso, phytopathologist and R&D director of Bio Insumos Nativa, recounts his experience in this trial that he carried out together with José Pablo Correa, TriNuts chestnut advisor.

Fungi are a constant problem in various crops, with this premise we decided to carry out a trial focused on a strategy of applying various biologicals to control Gnomoniopsis, a fungus that causes rot in chestnuts and also causes the leaves dry. Its presence causes post-harvest damage to rejected fruit and wood fungus.We carried out this test between 2019 and 2021 in orchards in two sectors of the country, Bulnes and Collipulli. It should be noted that the disease occurs when there are more rainy conditions.What we evaluated was a product called Mamull (WP), which is a biological fungicide that colonizes the points of cuts and wounds on the plant, preventing the entry of pathogenic microorganisms. Its strains present an effect of both competition, inhibition, and mycoparasitism.This product is used instead of painting pruning cuts, with Mamull (WP) these cuts are sprayed and colonized and wood fungi are prevented from entering, and it also eliminates the inoculum of the pathogen in the soil, either when the flower falls or the fruit from the previous year, the dead wood remains there as inoculums of these fungi. In this way, when applying it one colonizes it, reducing these sources of inoculum.

Strategy

Our strategy and execution began in the pre-flowering and beginning of flowering stage, where we applied Mamull to the leaf litter to control sclerotia and other reproductive structures and resistance to pathogenic fungi, both wood and fruit rot. Then, a resistance inducer was applied in tissues prior to infection that sought to increase the systemic response of the plant.After that, during flowering, Trichonativa was applied to colonize tissues susceptible to infection, prior to fruit formation. In order to continue in the pre-harvest stage where a resistance inducer was administered to increase the systemic response of the plant, to reduce the biotrophic infection phase, lengthening the puelche effect.To finish with the Mamull in the pruning period, where it was applied to the foliar pruning cuts and then to pruning remains in leaf litter, to avoid inoculum formation.

Positive results

The results were quite good on the incidence of this pathogen and its impact on chestnut yield. There was, in fact, a significant decrease in damage; some orchards even took the treatment and duplicated it commercially. An orchard went from 73% incidence to 23%.As it was difficult to monitor the fruit at destination, we took samples of the treated and untreated fruit and took them to the laboratory and made a humid chamber, where we put them in conditions that favor the pathogen and from there we evaluated when the reduction in damage. Reduced disease damage level by 50% to 70%.A dissemination activity was carried out with the producers where we showed them the program and the results; currently some of them are applying it commercially.