Fungicides increase wheat seed protection

The analysis of fungicides in the treatment of wheat seeds, conducted in six regions of Brazil in the 2024/25 harvest, confirmed the high efficacy of specific formulations against pathogens Fusarium graminearum e Bipolaris sorokiniana. The trials were part of the Cooperative Trials Network and used seeds from the 2023 harvest, marked by a high incidence of diseases caused by excess moisture.

Mixtures with benzimidazoles demonstrated control of up to 97,9% over F. graminearum. The combination of fluxapyroxad with mefentrifluconazole exceeded 96% control of B. sorokiniana. Products such as pyraclostrobin + thiophanate-methyl + fipronil and thiophanate-methyl + fluazinam maintained control of over 85% for both pathogens.

Seeds compromised by the previous harvest

The origin of the seeds significantly influenced the rates of natural infection. Samples from Cafelândia (PR) showed 64,8% contamination by F. graminearum. In Palmeira (PR), the highest incidence of B. sorokiniana reached 6%.

This health condition reflected the environment of the 2023 harvest, when heavy rains favored diseases such as head blight and leaf spots. Exposure to these pathogens compromised seed quality, increasing the risk of infection in the new crop.

Objective and methodology of the tests

The researchers evaluated nine fungicidal treatments against F. graminearum and eight against B. sorokiniana, in addition to positive and negative controls. The seeds were inoculated to simulate artificial infections of up to 20%. The evaluation followed the “blotter test” protocol, with seed incubation and microscopic analysis of the presence of fungal structures.

Each treatment was applied according to the manufacturer's recommendations, with 600 mL of solution per 100 kg of seeds. The statistical analysis used mixed linear models and the Tukey test (5%) to compare the effectiveness of the products.

Technical performance

in control of F. graminearum, the average natural infection rate was 7,8%. For B. sorokiniana, the average natural infection was 1,0%.

Among the treatments with good performance against both pathogens, two formulations stood out:

• pyraclostrobin + thiophanate-methyl + fipronil

• thiophanate-methyl + fluazinam

Both showed efficacy of over 85% in controlling the two diseases. The combination of ingredients allowed for a broader spectrum of action, with a significant reduction in the seed infection rate.