Mepiquat chloride, thidiazuron and ethephon applied on cotton in Ponta Porã, MS, Brazil

Abstract

The objective of this study was to evaluate the effect of doses of mepiquat chloride, thidiazuron and ethephon on cotton (Gossypium hirsutum L.), applied in parcels, and were surveyed in Itamarati Farm at Ponta Porã county. The mepiquat chloride doses were: (0.0; 12.5 + 12.5 + 25.0 = 50.0; 25.0 + 25.0 + 25.0 = 75.0; 0.0 + 50.0 + 50.0 = 100.0; 12.5 + 62.5 + 50.0 = 125.0) g ha^-1. The applications were made at 34, 47 and 63 days after emergence(DAE) in 1993/94 and at 42, 60 and 73 DAE in 1994/95. Thidiazuron was applied when 70% of bolls were opened at the doses 0.0, 45.0, 60.0 and 75.0 g ha^-1. Ethephon was applied seven days after thidiazuron, when 85% defoliation was observed, in the doses of 0.0, 960.0 and 1,440.0 g ha^-1. The experimental design used was strips with subdivided subparcelas. Mepiquat chloride decrease the number of unripe fruits, increased the weight of 100 seeds and the boll average weight. The defoliation percentage enhanced with increasing thidiazuron and ethephon doses. Mepiquat chloride x thidiazuron x ethephon interaction was significative to the percentage of opening bolls and production of cotton seed.