Growth reducers have been used successfully in wheat, preventing lodging, but use recommendation does not differentiate cultivar height. Experiments were conducted at the UEPG School Farm in 2005 to determine the rate and time of trinexapac-ethyl (Moddus) application in wheat cultivar. The experimental was arranged in complete randomized blocks, in a 2 x 2 x 6 factorial scheme, with three repetitions for each wheat cultivar. The treatments consisted of two nitrogen rates (50 and 240 kg ha-1), two trinexapac-ethyl application times (between first and second knot and between second and third perceivable knot) and six trinexapac-ethyl rates (0, 31.2, 62.5, 93.7, 125.0 and 156.2 g ha-1). Eight wheat cultivars of different lodging performances were used: OR-1, CD-104 and CD-105 (resistant), Alcover, Ônix and Vanguarda (moderately resistant), Supera (moderately susceptible), and CEP-24 (susceptible).Agronomical characteristics, yield components and yield were evaluated. Mild climate was not favorable to lodging occurrence, only observed for the lesser trinexapac-ethyl rates in CEP-24 cultivar. Nitrogen rate affected plant characteristics and the yield of some cultivars. The trinexapac-ethyl application stage did not substantially affect yield, but rather plant height, which became smaller the more delayed the application was. In general, yield adjustment equation in relation to the trinexapac-ethyl rates was quadratic, with yield increasing with increasing reducer rate, up to a limit, varying according to the cultivar.
plant height; lodging; yield; trinexapac-ethyl; Triticum aestivum
