Biological control tests for black crust in commercial rubber tree clones using Trichoderma sp. obtained from microfauna

The black crust has become a concern in the rubber tree (Hevea brasiliensis) culture, as it has been causing intense defoliation and consequently a decrease in latex production. Knowing that there are no fungicides registered for the control of this disease, this work aimed to evaluate the control of black crust through the use of Trichoderma isolates (isolates TC1 and AP1) obtained from leaves that showed the natural growth of this fungus. For this, tests were carried out in a greenhouse with rubber tree seedlings, investigating both the curative effect and the protective effect of the Trichoderma isolates, measuring the severity of the disease and the enzymes peroxidase and phenylalanine, which are linked to the expression of plant resistance. The TC1 and AP1 isolates were also tested on trees in the field, in this case the severity of the disease was quantified after four applications of these fungi. The application of the Trichoderma isolates in a greenhouse proved to be effective, mainly for curative treatments, as the two isolates controlled the disease and increased the activities of the studied enzymes. In preventive treatments, only the TC1 isolate showed disease control. In the field, however, the need for further tests with these isolates was seen, because although they had reduced the disease, there was no difference between them in relation to the control. Thus, although the isolates found have potential in controlling the disease, especially in seedlings, it is necessary to expand and improve field studies, and who knows, better assess the effectiveness of the Trichoderma tested for the control of black scab in the field.