Agronomic performance associated with fungicide use in subtropical corn farming/Desempenho agronómico associado a utilização de fungicida na cultura do milho em ambiente subtropical

Fungal diseases in Brazilian regions with tropical and subtropical climates reduce the production potential of corn crops. The use of fungicides is one of the strategies to maintain productivity. This study evaluated the agronomic performance and grain quality of corn hybrids associated with the preventive use of fungicides in subtropical environments. Six experiments were conducted in Santa Maria-RS, São Vicente do Sul-RS, and Frederico Westphalen-RS during two sowing seasons. The experiment was conducted in a randomized complete block design with a split-plot arrangement, in which the main plot consisted of two levels of the fungicide factor (with and without) and the sub-plot consisted of six levels of corn hybrids (AG9025, AS1730, P3016, MG300, DKB230, and FEROZ). Atotal of 216 experimental plots were evaluated for grain productivity, and eight plants per plot were evaluated for other traits, totaling 1,728 evaluated plants. Therefore, environmental conditions influence the interaction between the factors of fungicide use and hybrid cultivar positioning, with no significant interaction in years with a water deficit. Early sowings in subtropical environments indicate better agronomic performance and a lower percentage of moldy grains regardless of the cultivation location, contributing to grain quality. Key words: Zea mays L., cultural management, grain productivity, preventive chemical control, corn cultivars. No Brasil, em regiões de clima tropical e subtropical, as doenças fúngicas reduzem o potencial produtivo da cultura do milho. Uma das estratégias utilizadas para manutenção do potencial produtivo é o uso de fungicidas. O objetivo deste trabalho foi avaliar o desempenho agronómico e qualidade de grãos de híbridos de milho, associado ao uso preventivo de fungicida em ambientes subtropicais. Foram conduzidos seis experimentos, em Santa Maria - RS, São Vicente do Sul - RS e Frederico Westphalen--RS em duas épocas de semeadura. O delineamento experimental foi de blocos ao acaso com parcelas subdivididas, onde a parcela principal foi formada pelos dois níveis do fator fungicida (com e sem) e a subparcela pelos seis níveis do fator híbridos de milho (AG9025, AS1730, P3016, MG300, DKB230 e FEROZ). Foram avaliados 216 parcelas experimentais para a variável produtividade de grãos e oito plantas por parcela para os demais caracteres, totalizando 1.728 plantas avaliadas. Portanto, as condições ambientais interferem na interação entre os fatores uso de fungic