For the past 10 years, potato growers in the UK have been adjusting their weed control programmes to fit in with the many registration changes to herbicides – some actives have been lost altogether, while others have had dose rate changes.

Potato crop expert, Paul Goddard, of BASF, recently warned growers that it was inevitable that this change will continue into the next decade – but that BASF are working hard to develop new options to use in this crop, he said.

“There is nothing as constant as change. And in potatoes, with the registration changes we have seen and that are anticipated, I can only see the issue getting more complex,” he argued.

“We have lost a number of actives over the last 10 years, including linuron, which was the mainstay herbicide – the last on farm usage for linuron was June 3, 2018 – along with paraquat, which was used by most farmers.

“This year will be the last year for the use of diquat in potatoes with its last usage date being February 4, 2020. All other actives due for re-approval, such as metribuzin, clomazone and prosulfocarb, are being scrutinised and may be subject to label changes in the future,” pointed out Mr Goddard.

“We have been developing new options for potato weed control. Growers may be familiar with dimethenamid-p (DMTP) in other crops. It has shown excellent varietal crop safety in potato trials over the last few years and we will be continuing its development this year.

“This means that we may be looking at its registration for use in potatoes as soon as 2021. This active is mainly residual in its activity, but as it is adsorbed by the hypocotyl and coleoptile, as well as roots, it has a reputation for being less affected by soil moisture.

“Its weed spectrum of control includes cleavers, which can be a significant weed problem in potatoes as the leggy growth can smother the crop, interfering with spray coverage and harvest,” he added.

Dimethenamid-p is also strong on all species of cranesbill, shepherd’s purse, common poppy, red deadnettle, mayweeds, sow thistle, speedwell and forget-me-not.

“My feeling is that we may have to re-appraise what we do for weed control in potatoes and that the way forward is more likely to be a tank mix of three different pre-emergent actives all adding to a final solution. Some of these solutions will also be developed for other vegetable crops,” added Mr Goddard.

He pointed out that BASF is looking at the issue longer term, too, with totally new chemistry which has potential in potatoes offering both grass-weed and broad-leaved weed activity.

“We recognise that potato growing requires excellent and early removal of competitive weeds and that growers need herbicide solutions which are crop safe across all soil types and on all varieties. This is what we are working towards,” he said.