Gibberella and blast: how to identify in wheat

Gibberella and blast, despite presenting similar symptoms, have different etiologies and require different control strategies. Accurate identification allows effective management.

Fusariosis, also known as head blight, mainly affects ears and grains. It is caused by fungi of the genus Fusarium, Especially Fusarium graminearum, whose sexual phase is called Gibberella zeae.

Brusone, on the other hand, is caused by fungus Pyricularia grisea and is more recent in the Brazilian scenario, being detected for the first time in wheat in Paraná, in 1985, and in barley in the early 2000s.

Gibberella: whitish ears and grains with mycotoxins

Head blight is manifested by depigmented spikelets, whitish or straw-colored, which contrast with the green of the healthy ones. Affected grains appear wrinkled, wrinkled and white-pink in color. The problem is aggravated by the production of mycotoxins, such as vomitoxin, which are harmful to human and animal health.

This disease has gained strength in the South of Brazil in recent decades. Conditions of high humidity for more than 48 hours and temperatures between 20°C and 25°C favor the pathogen. Events such as El Niño intensify the incidence.

Conservation management, which keeps crop residues on the soil surface, helps to maintain the inoculum in the crop. In addition, head blight affects other crops in the production system, such as corn, triticale, oats and soybeans.

Brusone: lesion in the rachis and whitening of the ear

In brusone, the most obvious symptom appears on the ears: premature discoloration of the upper portion, above the point of infection in the rachis. Grains in these areas appear smaller and deformed. The disease can also attack leaves, with elliptical lesions with a light center and brown border.

High temperatures, cloudy days, prolonged dew and humidity above 90% favor the fungus. Spread by wind, the pathogen finds an ideal environment in the Midwest, where the humid climate and the presence of hosts such as rice and millet increase the pressure of the disease. In barley, outbreaks have caused losses of up to 35% in higher quality grains.

Anomalies that confuse the diagnosis

Several factors can cause similar symptoms. Frost, hail, pests such as stalk borers and stink bugs, and even physiological problems such as sterility, can cause white ears or malformed grains. These signs confuse technicians and producers, making decision-making difficult.

Examples include the stalk borer, which causes the ear to dry out with perforated stalks, and the black grub, which damages roots and prevents grain filling. Another common case is the white belly, linked to water and heat stress, which produces opaque and whitish grains.