Wheat: climate may favor the incidence of Fusarium head blight

Above-average temperatures and excess rainfall brought by the El Niño phenomenon form the perfect environment for the fungus that causes Fusarium head blight, the main disease of wheat. See research guidelines to reduce damage from the disease.

Fusarium head blight is a disease caused by the fungus Gibberella zeae (Fusarium graminearum) that attacks the ears of winter cereals, causing losses of up to 25% in grain yield, in addition to the potential for grain contamination by mycotoxins, which harm human and animal health. Giberella is the main problem affecting wheat, barley and triticale crops in Rio Grande do Sul, Santa Catarina and the central-southern region of Paraná, especially in El Niño years, when periods of high air humidity and rainfall are frequent. on consecutive days and temperatures between 24 and 30ºC, which increase the occurrence of an epidemic in the South Region.

As it is a fungus that attacks the ear, the wheat plant is more susceptible to Fusarium head blight from flowering until the final grain filling phase. In PR, according to Deral, almost half of the crops are in the flowering and fruiting phases, that is, susceptible to the incidence of FHB. In the states of RS and SC, crops are implemented later, with wheat heading expected between the months of August and September.

“We always advise the producer to monitor the crop to manage wheat diseases, but in the case of Fusarium head blight, the recommendation is to monitor climate forecasts to carry out preventive control and prevent the fungus from reaching the cob”, explains phytopathologist Cheila Sbalcheiro , from Embrapa Trigo.

According to Cheila, for better control of the disease it is necessary to protect the cob in advance. So, for example, with rain forecast in the next 24h to 72h, the advice is to apply the fungicide before the rain and repeat the operation after 7 to 10 days if there is another rain forecast.

What is the best control?

As to date there are no wheat cultivars with total genetic resistance to Fusarium head blight, chemical control has been the most recommended form of control, but the effectiveness varies between the active ingredients, and is also affected by the favorability to the development of the disease due to the environmental conditions and genetic differences between cultivars. In general, control efficiency with fungicides varies from 60 to 80%, but chemical management must be associated with cultivars with resistance, even if partial, and the application of the fungicide at the correct time.

To assist in choosing the most effective fungicides to control Fusarium head blight in wheat, providing protection of the productive potential of crops with a reduction in the volume of agrochemicals applied per area, in 2011 the Cooperative Testing Network was created, which brings together several research institutions and companies fungicide producers, aiming to evaluate, annually, the effectiveness of products (registered or in the registration phase) for the control of FHB, under natural infection, in the main wheat producing regions.

Currently, the following companies/institutions participate in the Cooperative Testing Network: G12 Agro, EEACG, 3M Experimentação Agrícola, CCGL, Agronômica, Instituto Agris, Embrapa Trigo, Agrotecno Research, Biotrigo Genética, 3tentos and Universidade Federal de Viçosa. In 2022, 12 research trials were conducted in eight locations: Guarapuava/PR, Palmeira/PR, Ponta Grossa/PR, Cruz Alta/RS, Jaboticaba/RS, Passo Fundo/RS, Santa Bárbara do Sul/RS and Viçosa/MG . Wheat cultivars with different reactions to Fusarium head blight and adapted to the test regions were used.

The treatments (commercial fungicides from different chemical groups, isolated or in formulated and registered mixtures, and products with Special Temporary Registration for experimentation) were defined jointly between research institutions and manufacturing companies (Bayer, Ihara and Syngenta). A control without fungicide (negative control), a control with fungicide (positive control) and three other treatments with different fungicides were evaluated. For each fungicide, three applications were carried out, the first at the beginning of flowering (25% to 50%), and the others at intervals between 7 and 12 days, according to the protocol, using a knapsack sprayer, with constant pressure, tip 110: 02 double fan without air induction and flow rate of 200 L ha-1.

All fungicides under analysis reduced the incidence and rate of FHB, with disease control efficiency of 60,9% to 82,7%.