Taking a broad approach to tackling herbicide resistance

Selecting the correct herbicide programme and good application practice is key to control of problem weeds and protecting chemistry for the future.

Using phenoxy and suphonylurea (SU) herbicides alongside each other is helping to tackle herbicide resistance in the latter group.

Nufarm agronomy lead Dan Macdonald says for the last 20 years there has been heavy reliance on SUs. He says: “They did what it said on the tin, giving good weed control, flexible application timing and were a flexible tank mix partner.

“But because we have relied on them so heavily in the last 20 years, there is resistance to this type of chemistry in broad-leaved weeds.

“Confirmed cases of broad-leaved weed resistance are increasing year-on-year where weed control has relied upon the use of sulphonylureas.

“In chickweed, mayweed and poppies, we are seeing either no control or reduced control.

“It depends on where you are in the country. We are seeing resistant chickweed in Scotland, whereas in East Anglia it tends to be poppy.

“Farmers need to control these weeds and phenoxies can play a part in this. There is no known resistance to phenoxy chemistry – it has a unique mode of action.

“I am not saying you should switch over 100% to phenoxies – SUs and phenoxies can complement each other.”

“A programme which combines phenoxies with sulphonylureas in tank mixes can deliver control of a wide spectrum of broad-leaved weeds.

“Adding fluroxypyr or florasulam to the mix, for example, gives an added effect of cleaver control.”

Combining an SU and phenoxy protects both chemistries and does not rely on one mode of action. It is also a good value option compared with other products on the market, he adds.

At last year’s CropTec Show, Nufarm published Rediscover Phenoxies – a Guide to Phenoxy Herbicides.

It was designed as a re-education guide for growers and agronomists on using phenoxies, including a description of their mode of action and which products control particular weeds. It will also be available at this year’s CropTec Show and can be downloaded here.

Source: FG Insight

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