Weed management practices for redroot pigweed control in maize

Redroot (Amaranthus retroflexus L.) and smooth pigweed (A. hybridus L.) are troublesome weeds in row crops in Serbia. Both species are very competitive, hosts for pathogens and insects, produce pollen which is highly allergenic; and the most recent research reported herbicide resistance in some populations across Serbia. An integrated approach for the control of both Amaranthus species must be evaluated and presented in order to reduce their negative potential in agriculture. In this paper, 9 yr results on redroot pigweed and smooth pigweed weed control are presented. In three different experiments, weed density and biomass of redroot and smooth pigweed were recorded: a) Crop rotation, b) row spacing and time of herbicide application, c) influence of nozzles and adjuvants. The influence of crop rotation and PRE herbicide mixture, PRE and POST mixture, and impact of nozzles and adjuvants were evaluated. PRE herbicide mix of S-metolachlor and isoxaflutole influenced 98.1% and 100% efficacy in the maize {Zea mays L.) continuous and in maize rotated with winter wheat (Triticum aestivum L.), respectively. The mixture of two herbicides, applied either in PRE or POST, resulted in 100% of control of both species. Finally, similar results were obtained for nicosulfuron application with extended range (XR) or turbo TeeJet induction (TTI) nozzles, and combined with nonionic surfactant (NIS) or ammonium sulphate (AMS) adjuvants. The novelty of obtained results indicates that only holistic approach based on different weed management practices can contribute to sustainable Amaranthus control. Key words: Adjuvant, cropping systems, herbicides, nozzles, weed control.