Commelina benghalensis is becomming the predominant weed invading eucalypts plantations in the State of São Paulo due to the continual use of herbicides and other control methods applied. Considering this, the objective of this work was to evaluate the effect of presence and control periods of Commelina benghalensis on Eucalyptus grandis initial growth, grew in winter and summer. A single eucalypt seedling was planted in a cement box and submitted to increasing periods of presence and control of Commelina benghalensis (0, 20, 40, 60 e 80 days in competition or not). Commelina benghalensis plant density was 4 plants.m-2 (in winner and summer conditions). The experimental period lasted for 100 days, after planting (DAP). The experimental design was arranged in a randomized block design (CRB) with 10 treatments and four replicates. The results for plant height, stem diameter, dry weights and leaf area showed that the period previous to interference (PPI), total period of interference control (TPIC) and critical period of interference control (CPIC), were 20, 60, and 20 to 60 DAP, respectively, in winner conditions. In summer conditions, TPIC was shorter than PPI (10 e 40 DAP, respectively), therefore it was not possible to determine CPIC in these conditions.
weed; critical period; control
