Seletividade de herbicidas em trevo-branco no estádio fenológico de expansão do primeiro trifólio

Abstract

RESUMO O trevo-branco (Trifolium repensL

White clover tolerance to herbicides applied at different rates and phenological stages

“…Machado et al (2013) assessing the selectivity of imazethapyr (100 g a.i ha ) applied to white clover seedlings at the two-leaf trifoliate growth stage reported phytotoxic levels of 1.5 and 9.7%, respectively, at 84 DAA, corroborating with the results of this work. Enloe et al (2013) studying white clover tolerance to multiple formulations of 2,4-D with imazethapyr reported effective weed control in mixed white clover/grass pastures without affecting white clover populations.…”

“…Machado et al (2013) evaluating 2,4-D applied at the first (16 days after emergence) and second-leaf trifoliate (27 days after emergence) growth stage reported lower toxicity for older plants. Young plants are more susceptible to herbicides than older plants, mainly because they have more Contracted form of glyphosate (Gly), 2,4-D and Paraquat + Diuron (Parq+di) applied at rates of 540, 1080, 1620; 400, 800, 1200 and 300, 600 and 900 g i.a ha -1 respectively.…”

“…Despite the fact that herbicide tolerance is the basis for the success of chemical weed control, the results available on white clover tolerance to herbicides are controversial given that some authors have reported that yield and persistence of the legume were markedly reduced (Griffin et al, 1984;Evers et al, 1993), whereas others have shown that although some herbicides can have initial phytotoxic effects, seedlings usually recover without severe damage (Machado et al, 2013) Selective post emergence herbicides are needed as emerging clover seedlings development is slow and not competitive with faster growing weeds (Schuster et al, 2013). Moreover, on crop livestock farms, corn may be cultivated using clover as living mulch or over its dead biomass, however, herbicide tolerance needs to be known for improved clover management.…”

Chemical Control of White Clover in Soybean Crops

“…Mc Curdy et al (2013) and Machado et al, (2013), studying herbicides selective to WC crop, have identified bentazon and imazethapyr as selective to crops, agreeing with the results obtained in this study (Table 1). …”

“…Thus, if unchecked after use, it remains in the area, becoming a competing plant with the subsequent grains crop. An aggravating factor is that this crop is tolerant to several herbicides used to control broadleaf plants (Machado et al, 2013;Mccurdy et al, 2013), which can hamper the chemical control of WC.…”