Growers are urged to consider a split dose post-emergence herbicide approach in maize crops this year to ensure early germinating weeds don’t run away and dent final yield.

Reports on maize drilling progress around the country paint a very mixed picture, with some growers or contractors all drilled up, while others still wait for wet-laying land to dry out.

Missed sprays

There are also plenty of reports that opportunities to apply pre-emergence sprays – which are widely recommended by agronomists to hold early germinating weeds – have been missed.

Certis Belchim technical manager James Cheesman says this could be placing too much emphasis on the traditional post-emergence herbicide timing at the 4- to 6-leaf stage of the crop.

This is risky, particularly in a late planting season. Currently, soil and air temperatures are rising and with plenty of moisture in the soil profile, conditions are conducive to growth of both crops and undesirable weeds.

“What we don’t want is broad-leaved species getting away from us and extracting moisture and nutrients from the soil and away from the maize. We know it’s a crop very sensitive to competition early on,” he explains.

Split dose

This leads James to promote a split dose post-emergence herbicide strategy in some situations this year.

These would include where no pre-emergence product was applied, or growers rely on a one-hit approach at 4-6-leaf. In either scenario, weeds can get away and stunt early crop growth.

A good option is to apply a 0.75-litres/ha dose of Diva (pyridate) at the 2-leaf stage as a holding spray, with the addition of mesotrione if the early broad-leaved weed burden is particularly high.

The main post-emergence spray then follows, comprising mesotrione with a nicosulfuron product like Fornet 6 OD, plus the addition of another dose of Diva, where appropriate, whilst staying within the total maximum total dose of 1.5-litres/ha.

Hit grassweeds

This will keep crops clean until shading by the crop canopy takes effect, says James.

“It also allows you to wait for grassweeds to germinate without other broad-leaved species getting too big, then take them out with the final pass using an appropriate tank-mix.”

Pictured: Maize smothered by weeds ©BLACKTHORN ARABLE