Wheat (Triticum spp.) represents approximately 30% of the world's grain production. In Brazil, according to data from the IBGE, by 2025, the South region will account for 86.3% of the country's wheat production and an estimated yield of 8.1 million tons is expected. The cereal is widely used in human nutrition, in the preparation of non-food products and in animal nutrition.
Yellow spot
Wheat crops can be affected by several diseases during their cycle. Yellow spot stands out as the main foliar disease of wheat in southern Brazil, causing significant losses in crop yield and grain quality when not managed properly. It is estimated that this disease can reduce productivity by 50% when conditions are favorable to the development of the fungus, and the damage can be greater in areas of wheat monoculture and in susceptible cultivars.
It is caused by Drechslera tritici-repentis, a necrotrophic fungus that survives in wheat straw left between one growing season and the next. In addition to wheat, barley (Hordeum vulgare), rye (Secale cereale) and triticale (Triticosecale) are reported as hosts.
The ideal weather conditions for development are air temperatures between 18ºC and 28ºC and a leaf wetness period of more than 30 hours. Therefore, in years with greater rainfall, damage to the crop tends to be more severe, as the conditions favor the development of the disease and make control with fungicides difficult, due to limited access of machinery to the field.
Symptoms
Symptoms appear soon after emergence, starting as small brown spots with a yellow halo. The lesion often grows and, as the leaf develops, becomes oval and occupies large areas of the leaf, progressing to necrosis.
Control
One of the main management strategies is crop rotation, which eliminates crop residues where the pathogen survives. It is recommended to use crops that are not hosts of the fungus, such as forage radish, canola, vetch and oats.
In addition, the cultivation of triticale, rye and barley in the area should be avoided, since they are also hosts of the fungus. Furthermore, studies show that it takes 18 months for the complete decomposition of cereal residues, therefore, two consecutive years without wheat are recommended in order to further reduce this pathogen in straw residues
The use of resistant cultivars, healthy seeds and seed treatment are also control strategies, as is maintaining the nutritional balance of the plant (avoiding nitrogen deficiency). Seed treatment with fungicides aims to eliminate or reduce fungi transmitted by seeds, preventing infections in the aerial parts of the plant. The use of fungicides with the active ingredient iprodione is the most effective molecule for controlling this fungus.
For the use of chemical control in aerial parts, products based on strobilurins and triazoles, or mixtures of these two chemical groups, are highly effective in controlling leaf spots. Consult the 3tentos fungicide portfolio with the chemical groups recommended on this website or with one of the consultants..
Text written by Lidiane Bilibio Bonfada and Luiz Henrique Manfio, members of AGR Jr. Agronomic Consulting, Junior Company of the Agronomy Course at UFSM Campus Frederico Westphalen, under the guidance of Professor Gizelli Moiano de Paula.
References
ALMEIDA, Juliano Luiz. Technical information for wheat and triticale: 2024 & 2025 harvests. Guarapuava: Agrarian Foundation for Agricultural Research, 2024. Available at: https://static.conferenceplay.com.br/conteudo/arquivo/infotecnitrigotriticalesafras20242025livrodigitalfinal-1721832775.pdf. Accessed on: May 9, 2025.
BIOWHEAT GENETICS. Yellow spot. Available at: https://biotrigo.com.br/pergunta/mancha-amarela/. Accessed on: May 7, 2025.
COSTAMILAN, Leila Maria et al. Leaf spots. In: EMBRAPA. Technological Information Agency. Brasília, DF: Embrapa, 2021. Available at: https://www.embrapa.br/en/agencia-de-informacao-tecnologica/cultivos/trigo/producao/doencas/manchas-foliares. Accessed on: May 9, 2025.
IBGE. In March, IBGE forecasts a harvest of 327.6 million tons for 2025. IBGE News Agency, 2025. Available at: https://agenciadenoticias.ibge.gov.br/agencia-sala-de-imprensa/2013-agencia-de-noticias/releases/43098-em-marco-ibge-preve-safra-de-327-6-milhoes-de-toneladas-para-2025. Accessed on: May 8, 2025.
PIRES, João Leonardo Fernandes. Wheat cultivation. 2nd ed. Passo Fundo, RS: Embrapa Trigo, 2014. 354 p. Available at: https://www.embrapa.br/en/busca-de-publicacoes/-/publicacao/1155370/cultivo-de-trigo. Accessed on: May 7, 2025.
SANTOS, A. F. dos; SILVA, J. R. da; OLIVEIRA, M. L. de. Curative application of fungicides and their effect on the expansion of wheat yellow spot lesions. Ciência Rural, Santa Maria, v. 43, n. 9, p. 1622–1628, Sep. 2013. Available at: https://www.scielo.br/j/cr/a/6bWvMTtPqN8gWcHcbSWRJjc/. Accessed on: May 7, 2025.
TELAXKA, Fábio Junior. Management of head blight and yellow spot in wheat crops. 2018. 61 p. Dissertation (Master's in Agronomy) – State University of Central-West, Guarapuava, 2018. Available at: https://www.unicentroagronomia.com/imagens/noticias/dissertacao_final_fabio_telaxka.pdf. Accessed on: May 7, 2025.
