Reductive disinfestation, soil desiccation and Trichoderma harzianum to control Phymatotrichopsis omnivora in pecan tree nursery

Abstract

In the laboratory, flooded soil with glucose, 0.5-4.0 mg g-1, the pH and potential oxidation-reduction (ORP) reached values of 6.2 and -250 mV, also, we observed up to 22 mmol L-1 of volatile fatty acids (VAFs). The supernatant of the soil was adjusted or not to pH ~ 4, then sclerotia of P. omnivora were submerged in it. The sclerotia died only in supernatants at pH ~ 4 that came from soil with 2.0 and 4.0 mg g-1 of glucose added. In the field, there were six treatments: a control or untreated soil (C); 55 t ha-1 of molasses was added and the ground was covered with plastic (M); inoculated soil with Trichoderma harzianum (T); dried soil (DS) and their combinations DS+M, DS+T and DS+M+ T. Where molasses was added, the pH and ORP reached 6.5 and -200 mV. The pH and ORP reached in soils with glucose and molasses are characteristic of soil reductive disinfestation (RSD). In the field, treatments were applied to the soil, with four plots per treatment and 12 pecan tree seeds were planted per plot. After three years, there was no difference in incidence and mortality of trees caused by P. omnivora, but the roots were invaded by Trichoderma sp.