By Mitchell Japp, PAg, Provincial Specialist Cereal Crops, Regina and Clark Brenzil, PAg, Provincial Specialist Weed Control, Regina
Kochia is becoming increasingly difficult to control due to the development of herbicide resistance. A new herbicide option for pre-emergent control is now available for use.
Authority 480 herbicide just recently received registration for pre-emergent use on spring wheat and durum wheat. Producers that have used Authority 480 in pulse crops, flax or sunflowers will be familiar with the product, but the use in spring wheat and durum is new.
Authority 480 can be applied to the soil surface prior to seeding, or up to three days after seeding (prior to emergence) to control emerging weeds. Note that only the low rate of 219 mL/ha (88 mL/acre) is approved in spring wheat and durum for kochia control only. However, there are several caveats that must be observed. The product is not suited to all areas or on all soil types. The product should not be used under the following conditions:
- On soils that are classified as coarse-textured soils;
- On soils that are fine-textured with less than 1.5 per cent organic matter;
- On soils with an organic matter content greater than six per cent; or,
- On soils that have a pH of 7.8 or greater.
Authority 480 herbicide is a Group 14 herbicide, with the active ingredient sulfentrazone included at 480 g/L. The product is soil applied with a minimum of 100 L/ha water (40 L/acre); the herbicide is taken up by roots and shoots of the weeds emerging from seed after application.
Layering herbicides can be an effective strategy to decrease the risk of escaped weeds that can build up populations of resistant types. Herbicide layering involves the use of herbicides from two or more modes-of-action (herbicide-resistance groups) for control of certain weeds at risk of developing herbicide resistance. The herbicide layering concept can utilize herbicides applied in the same season, whether herbicides are applied to the soil, as a pre-emergent surface, as an incorporated treatment or as a post-emergent foliar application.