Efficiency of fungicides to control Calonectria leaf blight in Eucalyptus

Calonectria leaf blight is one of the main diseases of eucalyptus in Brazil. In the field, phytopathogen infection can induce defoliation in plants, especially in the first months of planting, and consequently reduces their photosynthetic area. The objective of this work was to test whether the use of fungicides is efficient in controlling the disease. Control efficiency was tested through field tests, using the active principles Tebuconazole + Trifloxystrobin and Difenoconazole + Azoxystrobin at doses of 0% (as the control), 25%, 50%, 75% and 100%. A total of 150 trees were sprayed per treatment, considering 90 useful trees, with treatments arranged in rows. Three applications were carried out every two weeks. The levels of disease incidence were quantified using leaf traps installed in the basal region of the trees. Three traps were distributed per treatment, and the leaves contained in the traps were collected every two weeks, and the incidence of diseased leaves (%) in each trap was counted. The collected data were submitted to analysis of variance and the averages compared by Tukey's test at 5%. The control dose (0%) reached an average of 10.3% of incidence while conducting the work. The lowest incidence was registered with the use of the active ingredient Tebuconazole + Trifloxystrobin, with an average of 3.8%, 4.00% and 4.16%, respectively, at doses of 25%, 50% and 75%. The active ingredient Difenoconazole + Azoxystrobin showed a reduction in incidence at doses 75% and 100%, with an average of 5.9% and 5.66%, respectively. We conclude that the active ingredient Tebuconazole + Trifloxystrobin reduced the incidence of the disease at lower doses, while the active ingredient Difenoconazole + Azoxystrobin reduced the incidence at higher doses.