Períodos de interferência de erva-quente (Spermacoce atifolia) no crescimento inicial de eucalipto (Eucalyptus grandis)

The buttonweed (Spermacoce latifolia) is becoming a plant among the most current infesting eucalypts plantation in State of São Paulo due to the continual use of same herbicides and control methods. Owing this, this work aimed to evaluate the effects of periods of company and control of S. Iatifolia on the initial growth of Eucalyptus grandis, planted in winter and summer. Only one seedling of Eucalyptus was planted in amianthus cement box and submitted for crescent periods of company and control of S. Iatifolia (0, 20, 60 and 80 days in competition or not). The densities of plants of S. Iatifolia were 4 and 16 plants per m 2 (under winner and summer conditions). The experimental period was 100 days after the planting (DAP). The experimental design for both experiments was the completely randomized blocks (CRB) with ten treatments and four replicates. The results of plant high, stem diameter, dries weights and leaf area showed that the before interference period (BIP), whole period of prevention for interference (WPPI) and critical period of prevention for interference (CPPI) were 40, 60, and 60 DAR, respectively, under winner conditions. Under summer conditions, the WPPI and CPPI were 20, 80 and 20 to 80 DAR.