* camila@orgenetica.com.br

Wheat blast, caused by the fungus Pyricularia oryzae Triticum, can infect all the green tissues of the plant, such as leaves, stem, spikelets, awns and especially the rachis, where the disease is most destructive. Currently, the principal method to control the disease in wheat spikes is to incorporate the 2NS/2AS translocation, which comes from Aegilops ventricosa.

In Brazil, in 2023, of the 30 cultivars in the performance wheat cultivar trial, where the most important commercial wheat cultivars are tested, around 80% presented the 2NS translocation. However, the presence of 2NS does not correlate well with the resistance to the leaf lesions caused by Pyricularia. In the 2023 wheat season, the wheat crop in the South of Brazil was subjected to the El Niño system with high precipitation (> 1500mm Sept-Nov) and warmer temperatures, favoring the occurrence of diseases, including spike and leaf blast.

The elliptical lesions with a dark border and a silvery center appeared between seven days after infection and showed rapid sporulation, increasing the pressure of the disease in the field. The aim of this study was to test fungicides for controlling blast on wheat leaves, given that there are no specific fungicides recommended for controlling these symptoms.

The work was conducted in greenhouse with the cultivar “BRS 264”, which is susceptible to leaf blast. The experimental design was randomized with five replications and a total of 25 plants per treatment. It was tested 15 fungicides (application 24 hours before inoculation). Inoculation of conidia from infected rachis was carried out 35 days after sowing (Stage 13 of the Zadoks). The control of the disease was evaluated five and seven days after inoculation, scoring the severity of the disease on the leaves and the disease control index (%) – comparing the fungicide treatments with values of the control treatment (water application).

The fungicides composed of tricyclazole, commercial name Bim 750 and Bim Max (Tricyclazole and Tebuconazole), fungicides indicated for control of leaf and panicle rice blast, reduced wheat leaf blast severity by 97 and 98%, respectively.

The results showed that preventive application of fungicides enabled control of almost 100% of the blast lesions on leaves, which can be beneficial to reduce the inoculum pressure at heading stage in the field.