Splosh for dosh! Weed control in sugar beet

With the downward pricing trend of sugar beet, growers need to focus on doing what is absolutely necessary, but with the main focus of getting as much tonnage off the field as possible. Sugar beet develops slowly and is a very uncompetitive crop early on, allowing weeds to flourish and compete. Weeds with a high biomass, such as volunteer potatoes and thistles, will impede crop growth and shade the canopy, blocking out sunlight and having a significantly detrimental effect on yield. Other sugar beet crops have more straight forward and physically smaller weed problems such as polygonums and mayweeds, which will need controlling, too.

“With lowering sugar beet prices down to £24/tonne this year, the only way of making a good margin is to grow the heaviest crop you can. But you can reduce inputs by using the most appropriate herbicides at the most appropriate dose rates, providing you focus on controlling the truly competitive weeds,” says Peter Waite from Dow AgroSciences.

Covering Essex, Suffolk and Hertfordshire, Peter talks about the “splosh for dosh” concept. “This concept is about controlling weeds by using a low dose of Dow Shield 400 (up to 0.25 l/ha) to spice up the activity of metamitron plus oil. Dow Shield boosts the activity on groundsel, black bindweed, scented mayweed, scentless mayweed and thistles. By using the right herbicide combination early and often enough, you are protecting sugar beet and will be rewarded with higher yields – hence splosh for dosh!” says Peter.

He points out that in addition to this frequent low dose approach, sometimes Dow Shield 400 is used specifically to control the most competitive high biomass weeds in sugar beet, which are those that grow above the canopy. “One tall weed per square metre can cost 11% of yield. Being more specific, research shows that 5 potato volunteers per square metre can result in yield loss of 16.5 t/ha of beet, as well as running the risk of being a source of potato blight and Potato Cyst Nematodes (PCN).”

“Because there is a big overlap between sugar beet and potato growing areas, beet will always run the risk of potato volunteers as a potential weed problem. This year we didn’t have any winter frosts to reduce the daughter tubers in the ground, so we are expecting more volunteers than usual in beet.”


Dow Shield 400 is considered to be the single most important herbicide to use on volunteer potatoes in sugar beet. But its use should be part of an integrated control programme across the whole farm rotation, using other products in other crops, such as Fazor (maleic hydrazide) in potatoes.

“For potato volunteers in sugar beet, the first treatment should start when the first emerging volunteer potatoes are at 5 to 10 cms and sugar beet at second true leaf. A follow up spray can be applied 14 days later., but you must be finished by the end of June. Mixes with ethofumesate or trisulfuron work more quickly. Controlling these pernicious weeds with a herbicide programme applied in a number of splits, sugar beet yields are protected,” says Peter Waite.

He goes on to consider another high biomass weed nuisance - thistles. “Just one creeping thistle stem per square metre can reduce sugar beet yields by 1 t/ha. Dense stands of tall sappy stems compete directly with the sugar beet and control should start when weeds are small. Creeping thistles, spear thistles and sow-thistles are all controlled by Dow Shield 400 at 0.25 l/ha plus a coformulation of desmidipham + ethofumesate + phenmidipham at 2 l/ha plus either trisulfuron-methyl at 20 g/ha or metamitron at 1 l/ha at the rosette stage of the crop. This can be followed up by Dow Shield 400 at 0.5 l/ha 3 to 4 weeks later.”

Peter reminds growers that Dow AgroSciences continues to invest in Dow Shield 400 by reformulating it to double strength formulation and by packaging it in a new style container with no induction seal or foil to get rid of. “This makes the whole spraying process much quicker and easier. It simplifies waste recovery, with fewer packs to dispose of and also reduces point source contamination risk.”