Eight actives remain available for annual broad-leaved weed control in conventional sugar beet following the loss of desmedipham. However, it is possible to cover the weed spectrum with the ones which remain, according to Pam Chambers, UPL national influencer UK and Ireland.
Speaking at the British Beet Research Organisation (BBRO) BeetTech21 webinar, Ms Chambers said: “There will need to be more attention to detail when looking at product rates and adjuvant uses. More thought will need to go into programmes but the information is there on BBRO charts and in manufacturers’ information on what rates are supported at key beet growth stages.
“The key thing to remember is phenmedipham is not equal to desmedipham gram for gram. Growers will need more phenmedipham in programmes, especially during colder conditions. All currently marketed straight phenmedipham individual product labels have a maximum total dose restriction of six litres/hectare and a maximum individual dose rate of three litres/ha.
“Last year some agronomists would have liked to have applied more than six litres and some achieved this by switching brands.”
Ms Chambers also warned growers who may not have used straight phenmedipham for some time to be careful over dose rates.
“Historically phenmedipham products contained 114g a.i./litre, compared to 160g a.i./litre of current products.
The rates are not comparable gram for gram, as originally phenmedipham was formulated as an EC [emulsifiable concentrate] compared to the SC [suspension concentrates] of today. EC formulations were recognised as being ‘hotter’ on the crop and the weeds.”
When considering whether to use a pre-em herbicide, Ms Chambers recommended always using one for black-grass control other than on organic soils and suggested ethofumesate and metamitron.
“Another situation is where growers are nervous about being able to apply a post-em in a timely manner which was an issue last year because of variable crop and weed emergence. Putting on a pre-em buys a bit of extra time before needing to put on a post-em.
“If you have fat hen, mayweed or knot grass metamitron can be a useful pre-em.”
Although dry conditions may deter growers from applying a pre-em because they are not as effective in such conditions, activity will still kick in after rainfall, she said.
Launched to the market last season, the Conviso Smart system comprising a broad-spectrum herbicide product (foramsulfuron + thiencarbazone-methyl) and sugar beet varieties tolerant to its active substances performed well, according to independent agronomist Penny Oakes.
She said: “Control of weed beet has been phenomenal. Broad-leaf and grass-weed control was exceptional but I can confirm that speedwell is not controlled by Conviso One.”