With the high demand for Avadex Excel 15G (tri-allate) as an integral part of a successful black-grass control programme, it is important that users, both experienced and novices, understand how to get the best from the application of this chemical.

Dr. Dominic Lamb of Gowan says Avadex has become an essential part of any weed control programme, but it is not ‘the magic bullet’. “It improves the performance of the herbicide stack, which most farmers acknowledge is needed for good grass-weed control. It also needs to be applied correctly at the right time by well calibrated machinery. If not, it is asking too much of the chemical.”

“It is best positioned as the starter herbicide and applied pre-emergence, forming a chemical barrier through which germinating weeds grow. As the weeds absorb the chemical, an overall boosting effect is seen to the efficacy of the herbicide programme.”

Dr Lamb says that black-grass control needs to be based around a tri-allate and 240 gm/ha flufenacet programme. “It doesn’t matter which comes first, as results and crop safety have been no different.”

He advises particular attention must be paid to seedbeds and drilling depth. “Avadex is best applied to well-prepared moist seedbeds. Very cloddy seedbeds should be avoided and loose and puffy seedbeds consolidated before drilling. Drilling depth is crucial so make sure that drilling depth is correct - for wheat, triticale and rye this is 4 cms and for barley 2.5 to 4 cms.”

He also says that Avadex needs some moisture to be activated, although research work shows that it is the least affected by dry condition of the residuals. “Work at NIAB looked at several physical and chemical criteria including Vapour Pressure and Henry’s Constant (dimensionless) to help predict herbicide activity in dry soils. Field results confirmed that that flufenacet, the bedrock of all pre-em programmes, was vulnerable to dry conditions, as was DFF. Prosulfocarb and flupyrsulfuron were a little less vulnerable and pendimethalin less so. The efficacy of tri-allate was the least affected by dry conditions.”

When it comes to application, Dominic says that the applicator must be fit for purpose and set up correctly for Avadex granules. “It is pretty obvious but it is surprising how machines are not calibrated as regularly as they should. You need to calibrate the machine, or get it calibrated for you, to make sure that the granules are being spread correctly at the right dose and pattern. Make sure the spread pattern is even and the outlets are at the same height and angle. If the machine is not set up correctly, you will see stripes of uncontrolled weeds across the field.”

Dominic Lamb says Avadex must not be applied in strong winds as this disrupts the spread pattern and don’t consolidate after application as you may alter drilling depth. “The label also says do not apply to soils with more than 10% organic matter (as is the case with all residuals), do not under sow with grass species (as they will be controlled by Avadex) and do not sow oats or grass crops within one year of applying Avadex.”

He concludes by saying that Avadex has become a key component in any black-grass control programme. “Tri-allate works in a different way to almost all other cereal graminicides and is once again finding a key position in many weed control programmes, its robust performance proven with over 50 years of use in the UK.”

“Don’t forget that it is recommended in winter barley as well as winter wheat. There are fewer actives that can be used in winter barley, so it is again a useful starter herbicide that can be followed by flufenacet products. It also controls wild-oats, volunteer (tame) oats and moderate populations of Italian rye-grass and annual meadow-grass. Applied pre-emergence of weeds, you can also expect useful control of annual broad-leaved weeds including cleavers, charlock, chickweed, common poppy, field pansy, field speedwell, forget-me-not, fumitory, ivy leaved speedwell, mayweed spp and red dead-nettle. Its broad-leaved weed control is often underestimated.”

For further information, please contact Dr. Dominic Lamb, UK and Ireland Business Manager for Gowan on 07584 052323.