In recent years, there has been an increasing investment in technology and the cultivated area of wheat (Triticum aestivum) in the Southern region of the country as an additional source of income for many properties. Wheat, as the main winter crop, has often been treated as a soil cover option in previous seasons, with low investment and productivity. However, in recent years, the crop has been treated differently, attracting the attention of producers and resulting in a significant increase in cultivation area. In fact, in the last harvest, Rio Grande do Sul surpassed the state of Paraná in terms of cultivated area. When considering wheat crop establishment, seed treatment (ST) plays a key role. This tool assumes fundamental importance for pest and disease control in the early stage of crop development.
Several pathogens that contribute to the epidemiological framework of economically important diseases in wheat can be transmitted through seeds, while others remain in crop residues for extended periods. Additionally, important pests such as cutworms, aphids, and caterpillars can cause immediate damage after wheat sowing or emergence, compromising the final grain yield.
Main diseases and pests controlled:
Seed treatment in wheat can be indicated for the control of diseases caused by fungi that initiate the epidemiological framework through the inoculum present in the seeds themselves or in crop residues. Among these phytopathogenic fungi are the causative agents of yellow spot (Dreschslera tritici-repensis), brown spot (Bipolaris sorokiniana), loose smut (Ustilago nuda f. sp. tritici), and common root rot (Fusarium graminearum and Bipolaris sorokiniana). Usually, wheat crops that have had incidence of leaf spots and common root rot retain the primary inoculum of the causal agents in the crop residues for approximately 18 months.
However, due to the potential of the pathogens to reach the spikes and infect the developing grains, harvested seeds can become an important means of dissemination, allowing immediate infection of the seedling upon germination. Therefore, treating the seeds with specific fungicides allows for the eradication of seed-associated pathogens and protects seedlings from infection during the pre-establishment phase of the crop. The causal agent of powdery mildew (Erysiphe diffusa) can also infect plants in the early stages of development. Although it does not persist in the seeds or crop residues from one season to another, the disease can also be initially controlled through seed treatment. In this case, systemic fungicides with prolonged residual effects are used. Regarding pests that attack in the early establishment of the crop, seed treatment can assist in control and minimize the damage caused by key pests such as pasture scarabs (Diloboderus abderus) and wheat scarabs (Phyllophaga triticophaga), cereal aphids (Rhopalosiphum padi), greenbug aphids (Schizaphis graminum), corn rootworm (Diabrotica speciosa), and occasionally caterpillars. Insecticide seed treatments have been used as a preventive strategy against these pests, hindering the occurrence of high pressure during the early stages of wheat cultivation. The action of insecticides applied via seed control pests from sowing or emergence until the beginning of tillering.
Which active ingredients to use and how to improve efficiency
Usually, the most commonly used fungicides for wheat seed treatment have specificity regarding the genera or families of fungi. Therefore, seed health analysis is essential to identify the incidence and which pathogens are present in the seeds, as it is the first step in deciding which active ingredients should be used.
For the eradication of foliar spot inoculum in wheat seeds and the protection of seedlings against infection by pathogens present in the area, it is recommended to use fungicides from the Dicarboximide group, such as Iprodione. For powdery mildew control, the most efficient fungicides at the moment are the triazoles (inhibitors of sterol demethylation group).
The fungicide Carbendazim (Methyl benzimidazole carbamate group) was widely recommended for controlling F. graminearum through seed treatment. With its prohibition from commercialization in 2022, the management of this pathogen became even more dependent on integrated disease management, mainly through crop rotation with non-host species.
For preventive control of pests, systemic insecticides from the Neonicotinoid chemical group are generally used. It is important to emphasize that the treatment's efficiency will depend mainly on the quality of seed surface coverage. Therefore, to completely eradicate the pathogens present in the seeds and enable the protection of plant structures from initial pest attacks, it is essential to provide homogeneous and complete coverage with the recommended fungicides and/or insecticides, always following the recommended doses.
Is seed treatment sufficient?
The management of pests and diseases in wheat cultivation should be done in an integrated and sustainable manner. In this sense, the efficiency of seed treatment can be significantly increased when integrated with other phytosanitary control methods. Therefore, choosing cultivars adapted to the cultivation region, eliminating host plants, sowing at the recommended time and under conditions that guarantee rapid emergence, implementing crop rotation, and selecting resistant cultivars are important to promote rapid and vigorous crop establishment and reduce the pressure of pests and diseases in the early stages of crop development.
Text written by Caetano Rocha and Maurício Piccoli Bonatti, students of the Agronomy course at UFSM Campus Frederico Westphalen, members of the Tutorial Education Program - PET Agrarian Sciences, under the supervision of tutor Professor Dr. Claudir José Basso.
References:
GUTERRES, C. W.; BRUINSMA, J. S.; SEIDEL, G.; MARTIN, T. N. Tratamento de sementes em trigo para prevenir doenças. Pelotas: Revista Cultivar, 2020. Available at: [link]. Accessed on April 25, 2023.
HOSSEN, D. C. et al. Tratamento químico de sementes de trigo. Pesq. Agropec. Trop., Goiânia, v. 44, n. 1, p. 104-109, jan./mar. 2014. Available at: [link]. Accessed on April 25, 2023.
MORI, C. de et al. Trigo: o produtor pergunta, a Embrapa responde. Brasília: Embrapa, 2016. 309p. Available at: [link]. Accessed on April 25, 2023.
PEREIRA, P. R. V. S. da; JUNIOR, A. L. M.; LAU, D.; PANIZZI, A. R.; SALVADOR, J. R. Manejo de insetos-praga. In: BORÉM, A.; SCHEEREN, P. L. (ed). Trigo: do plantio à colheita. Viçosa: Editora UFV, 2015. 185-202p. Disponível em: https://www.embrapa.br/busca-de-publicacoes/-/publicacao/1022684/trigo-do-plantio-a-colheita. Acesso em: 25 abr. 2023.
REIS, E. M.; CASA, R. T.; ZOLDAN, S. M.; GERMANO, B. C. Manejo de doenças. In: BORÉM, A.; SCHEEREN, P. L. (ed). Trigo: do plantio à colheita. Viçosa: Editora UFV, 2015. 185-202p. Disponível em: https://www.embrapa.br/busca-de-publicacoes/-/publicacao/1022684/trigo-do-plantio-a-colheita. Acesso em: 25 abr. 2023.
SALVADORI, J. R. Controle de pragas iniciais em trigo. Pelotas: Revista Cultivar, 2018. Disponível em: https://revistacultivar.com.br/artigos/controle-de-pragas-iniciais-em-trigo. Acesso em: 25 abr. 2023.
