- As the names suggest, preemergence or preplant herbicides are applied to the soil at the time of planting oats. Recommended chemicals include triallate, mesotrione or flucarbazone. All chemicals are sold under different brand names. For best efficacy, these herbicides are applied prior to the germination of weed seeds. Preemergence herbicides are ineffective on already growing or established weeds.
- For weeds already growing in oats, use the recommended postemergence herbicides. These include a number of chemicals such as tribenuron, thifensulfuron, carfentrazone-ethyl, dicamba, bromoxynil, mesotrione, MCPA, fluroxypyr or clopyralid. Often combining one or two postemergence herbicides helps to provide a more effective weed control than a single product.
- The repeated use of the same herbicide for the control of persistent weeds results in the development of resistance in weeds. The recommended way to deal with resistant weed varieties is to rotate herbicides in a manner in which chemicals with a similar mode of action or group number are not applied repeatedly on the same crop or rotational crops. Integrated weed practices such as tillage, cultivation, fertilization and crop rotation help deal with resistant weeds.
- Proper cultural management helps to reduce weed infestations in oats. This reduces the amount and cost of herbicides required for weed control later. Cultural management practices include the use of clean seeds and planting at the recommended rate. Plant small grains such as oats early so that the crop can compete better with weeds. Early planting also helps to control warm-season annual grassy weeds. It also is important to keep in mind the effectiveness level of the selected herbicide and compare it against crop tolerance and total cost of herbicides. Make sure weeds are identified prior to selection of herbicides.