Radicular exudation of glyphosate by Brachiaria decumbens and its effects on eucalypt plant

Eucalypt plants commonly present symptoms of intoxication in areas where glyphosate is used. One possible way of contamination is through radicular exudation of glyphosate by the treated weed and later, plant absorption. This study aimed to evaluate glyphosate exudation by Brachiaria decumbens and its effects on eucalypt plants when C-14-glyphosate, mixed to the solution of the commercial product Scout (R) was applied. Seedlings of two eucalypt clones (UFV05 and UFV06) were cultivated in pots, intercropped with Brachiaria decumbens, on two types of soil (clayey and sandy). At 35 days after transplantation, 50 mu L of the mixture was applied on brachiaria by using a precision micro-syringe. After application, 2, 8,16 and 24 days, samples of eucalypt plants were collected and fractioned in the primary apices, secondary apices, leaves and roots, following the usual methodology to determine radioactivity. Symptoms of intoxication were not observed in any eucalypt plant evaluation. However, C-14-glyphosate was found in all plants, regardless of the soil type, clone or evaluation time, with the highest concentration being found in the sandy soil. Results show radicular exudation of glyphosate by B. decumbens and its absorption of by eucalypt plants through roots. However, concentrations lower than necessary may cause crop intoxication.