Caused by the fungus Magnaporthe oryzae, rice blast is one of the most common diseases in rice worldwide and also in Portugal, affecting all producing basins, from Mondego to Tagus, Sorraia and Sado.

Magnaporthe oryzae‘s attack may result in losses in production of around 50%, as happened to rice farmers in Tejo-Sorraia in 2018. However, losses in production are more or less considerable depending on the variety of rice and climatic factors, like humidity and temperature. In cultivation sites where a relative humidity of 95% prevails with an average temperature of 26 °C/ 27 °C, the risk of infection and spore spreading is high.

The presence of rice blast is visible by the appearance of circular or elliptical spots, presenting a grayish center surrounded by reddish-brown edges, and can manifest itself in all aerial parts of the plant and at any time of its development process, from the early stages to the milky grain phase.