Optimising time of planting and herbicide aplication for control of problem weeds in maize

Abstract

Field trials in Waikato Bay of Plenty and Manawatu investigated the efficacy of pre and postemergence herbicides for weed control in maize crops planted early mid or late season with prior cultivation or into a stale seedbed Achieving good control of broadleaf weeds was easier than for annual grass weeds Some weed species germinated over a long period from spring to summer months The residual activity of preemergence herbicides was not sufficient for seasonlong control of such weeds in the early and mid planted crops and a postemergence herbicide was essential to control them and to maintain grain yields When grass weeds were dominant the pre and postemergence combination still did not provide season long control in the early plantings In late planted crops weed control was also poor in the absence of a postemergence herbicide even though few weeds were present at the postemergence application time The weed seedbank was reduced where good weed control was achieved