Sintomas de fitotoxicidade em mudas de café submetidas à herbicidas inibidores da protox

This research aimed to evaluate the influence of the herbicides flumioxazin, oxyfluorfen and carfentrazone-ethyl in initial growth of coffee seedlings under field conditions, identifying the phytotoxicity symptoms caused in plants. The experiments were performed in a randomized block design with four replicates and six doses of the herbicides (0%, 10%, 40%, 70%, 100% and 200% of the recommended dose). The herbicides were applied directly onto the plants using a knapsack sprayer pressurized by CO2 and regulated to 45 kgf/cm². After the pulverization, the seedlings remained in field for 45 days, being performed the identification and observation of the symptoms of phytotoxicity. The observation of the phytotoxicity symptoms was done each two days, by the capture of images and the comparison of plants that received herbicides against the pattern. At the end of the experiment were evaluated the number of leaves, stem diameter and plant dry weight. In the herbicides oxyfluorfen, carfentrazone-ethyl and flumioxazin, from the dose of 10%, the main symptom of phytotoxicity observed was the formation of irregular necrotic spots on the leaf surface, mainly in the apical regions. The oxyfluorfen and carfentrazone-ethyl herbicides, on all studied doses, despite causing phytotoxicity and light injuries in coffee seedlings did not affect its growing. The flumioxazin herbicide showed higher phytotoxicity in plants, significantly reducing their growing compared to control, starting at the 10% dose.Objetivou-se avaliar os sintomas de fitotoxicidade causados por diferentes doses dos herbicidas flumioxazin, oxyfluorfen e carfentazone-ethyl em mudas de cafeeiro. O experimento foi realizado em delineamento de blocos casualizados, com quatro repetições, e seis doses de cada herbicida (0%, 10%, 40%, 70%, 100% e 200% da dose recomendada). Cada parcela foi composta por cinco mudas de cafeeiro da cultivar Mundo Novo, apresentando de 4 a 6 pares de folhas, sendo posteriormente fixadas com o saquinho em estacas com espaçamento de 0,40 x 0,40 m. As aplicações foram feitas diretamente sobre as plantas por meio de um pulverizador costal pressurizado por CO2, regulado a 45 kgf/cm². As mudas permaneceram no campo por 45 dias após as pulverizações, sendo realizada a identificação e observação dos sintomas de fitotoxicidade a cada dois dias. Ao final do experimento foi avaliado o número de folhas, o diâmetro de caule e massa seca da parte aérea das plantas. Os herbicidas oxyfluorfen e carfentrazone-ethyl, apesar de causarem fitotoxicidade e injurias leves nas mudas de cafeeiro, não afetaram o seu desenvolvimento. O herbicida flumioxazin apresentou maior fitotoxicidade nas mudas, reduzindo significativamente seu desenvolvimento em relação a testemunha