Sugar beet and maize will be vying for their share of sprayer time over the next couple of weeks to keep competitive weeds at bay, says Agrovista agronomist Craig Green.
Growers who applied a pre-em to sugar beet can allow crops to grow a bit longer and weather before returning with the sprayer with the first post-em spray, reducing the risk of checking crop growth.
Most sugar beet crops under Craig’s care will have received a pre-emergence herbicide, given this season’s adequate soil moisture levels.
“Growers’ decisions are driven by soil moisture – many prefer to leave the pre-em and go early post-emergence when seedbeds are dry, but this year we’ve had plenty of rain to activate chemistry,” says Craig.
Subsequent advice will be tweaked according to whether fields received a pre-em spray or not.
Craig’s pre-em recommendations will have bought some flexibility in the post-em programme. He recommended chloridazon + metamitron, as Volcan Combi at 3-litres/ha, or straight chloridazon as Pyramin at 2.5kg/ha where fat-hen was absent.
The chloridazon will have given good initial control of black bindweed, which is rife in many beet areas, while metamitron will have boosted activity on early-emerging fat-hen.
“Chloridazon can only be applied pre-emergence so if you miss this timing you are left with phenmedipham post-emergence, which is less effective on black bindweed,” says Craig. “Once the weed gets to one true leaf, it is difficult to take out.”
Growers who applied a pre-em can allow crops to grow a bit longer and weather before returning with the sprayer with the first post-em spray, reducing the risk of checking crop growth.
Craig recommends Betanal Maxx Pro at 1-litre/ha when beet cotyledons are fully expanded. “The product contains ethofumesate, which tops up residual activity, and phen- and desmedipham that provide strong contact activity against a range of grass weeds. It also contains Lenacil, which hots the mixture up on weeds.”
He will add 1-litre/ha of Target (metamitron) where fat-hen is a problem. Another favoured ingredient in the mix is KryptoN, a 28 per cent liquid nitrogen formulation that acts as a crop safener.
“I really rate it – sugar beet can break down desmedipham and phenmedipham but it needs nitrogen to do it, so this will minimise growth check.”
Crops that did not receive a pre-em will need treating earlier, before beet cotyledons have fully expanded. “I’ll use Betanal Maxx Pro, but at no more than 0.75-litres/ha, with Target at 1-litre/ha. I’ll add KryptoN at 0.75-litres/ha.”
The mix is less flexible than the one following a pre-em, and doesn’t allow much leeway if weather conditions hamper spraying. “You also need to be careful of spraying if we get warm days and cool nights – large temperature differences can stress small beet plants.”
Subsequent contact sprays will depend on the weather. If it is set fair, he’ll use the FAR little and often approach; if the forecast is doubtful or where sprayer time is limited he’ll go for the Broadacre approach.
“FAR does result in a cleaner crop with less risk, but for growers with big acreages or who rely on a contractor applying just two further applications in two big hits does have its advantages.”
He’ll use Betanal Maxx Pro plus Target as appropriate, or switch to Beta Team (desmedipham + ethofumesate + phenmedipham) to shave costs.
Debut (triflusulfuron-methyl) will be added to control fumitory, volunteer OSR and cleavers, while grass-weed control will require a pass with Falcon (propaquizafop). Dow Shield (clopyralid) will take out creeping thistle.
Early post-em for maize?
Timely weed control will be key this season with weeds ready to grow away rapidly in moist soils, Craig advises.
“Crops will need 1,200g/ha of pendimethalin pre-emergence to provide early control of annual meadow grass and broad-leaved weeds.”
An early post-emergence should be planned if the weather stays cool, when the maize has two true leaves, as the crop could get held back while weeds continue to grow.
“Maize can suffer from cold shock and turn yellow. I prefer to use Templar (bromoxynil + terbuthylazine) at 1-litre/ha to take out the early weed flush, or straight bromoxynil, such as Buctril at 0.6-litres/ha.”
If the weather warms up, he’ll delay to the normal 2-4 crop leaf timing, based on Callisto (mesotrione) at 1-litre/ha to control broad-leaved weeds.
Where grass weeds feature or where a mesotrione-sensitive crop such as sugar beet or potatoes will follow the maize, he’ll choose Maister (foramsulfuron + iodosulfuron) plus adjuvant Mero.
“At either timing if crops are showing any signs of yellowing or slow growth I’ll add 1-litre/ha of P-Kursor, a rapidly absorbed form of phosphite that is quickly translocated to roots and shoots. This will improve plant growth in cool conditions and help prevent any growth check from the herbicide.”
*Craig Green is an agronomist with Agrovista, based at Great Ellingham, Norfolk – [email protected]sta.co.uk.