For the last ten years or so, 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; others have had dose rate changes. Potato expert Paul Goddard of BASF warns growers that it is 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.

“There is nothing as constant as change,” Paul says. “And in potatoes with the registration changes we have seen and that are anticipated, I can only see the issue getting more complex. We have lost a number of actives over the last ten years including linuron which was the mainstay herbicide (last on farm usage for linuron was 3 June 2018) along with paraquat used by most farmers. This year will be the last year for the use of diquat in potatoes with its last usage date being 4 February 2020. All other actives due for reapproval such as metribuzin, clomazone and prosulfocarb are being scrutinised and may be subject to label changes in the future. 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. We may be looking at its registration 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 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. 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 own feeling is that we may have to reappraise 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,” says Paul.

He says that BASF is looking long term too with a totally new chemistry with 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.”

Pictured: Paul Goddard