Brown spot disease (of Rocha pear)

This disease was confirmed for the first time in Portugal in 1996 in the Rocha and Passe Crassan pear varieties, currently assuming an epidemic situation in the so-called Oeste region of the country. Its effects are so devastating that, for example, between 2014 and 2016, it caused losses of approximately 30 million euros in the Rocha pear industry, according to data presented in 2017 by INIAV, at the Technical Days about Fruit Crops.

Caused by the fungus Stemphylium versicarium, the brown spot disease of the pear tree attacks the leaves and fruits, and the symptoms vary according to the variety of the pear tree. The spots tend to invade the entire leaf, along the central vein, causing it to dry out and fall; in fruits, they appear on the faces most exposed to the sun and spread to the whole fruit if the climatic conditions are favorable to the proliferation of the disease.

Also present in the orchard at the time of flowering, infections by the fungus Stemphylium vesicarium can occur in flowers, namely in anthers and sepals. And when there are favorable conditions of temperature and humidity, the fungus develops and infections increase, sometimes leading to the fall of the fruits.

The incidence of the disease depends on the varieties of pear and the level of ripeness of the fruits, and seems also to be linked to the alteration of treatment schemes for scab (one of the most important diseases of pome trees in the world, such as pear and apple trees), in particular the use of active substances that only control the scab and have no effect on brown spot disease.