Keeping on top of weeds will be particularly important this spring after difficulties with autumn control and a wet, mild winter. But a new herbicide is on hand to help.
From March 1 oilseed rape growers will have a new herbicide for broad-leaved weeds in their armoury following the launch of Korvetto (Arylex Active + clopyralid) by Corteva.
It will ultimately supersede the company’s herbicide product Galera (clopyralid + picloram) as a spring ‘tidy up’ for oilseed rape if weeds have got away over winter, says Corteva account manager Peter Waite.
“It will keep crops clean as we get into stem extension and flowering. It tackles key weeds that will pop up above a crop and cause difficulty at harvest. It is strong on cleavers, mayweed and thistle. At a 1-litre/hectare rate, Korvetto is delivering 20g more clopyralid than Dow Shield and 5g of Arylex gives a boost on cleavers, fumitory, cranesbill, dead nettle, poppy, sow thistles and creeping thistle.”
Corteva’s oilseed rape category manager John Sellars says: “Even farms which apply good autumn herbicide programmes in a timely manner will usually face a late winter and early spring-germinating broad-leaf weed burden.
“Korvetto will be a very good option for UK farmers because it will control many of the weeds found in oilseed rape crops germinating as daylight hours increase and temperatures rise.”
The new herbicide is applied from growth stage BBCH30, the same timing as for Galera, explains Mr Waite. “It is before the flower buds are visible, just before they go over the top of the canopy. This is usually in early March depending on where the crop sits.”
Corteva says its Galera product has played a key role in many spring-applied oilseed rape herbicide programmes for many years. But Mr Sellars says Korvetto represents a step-change in performance over current standards.
“Korvetto contains clopyralid but is significantly beefed up by the inclusion of Arylex – the unique herbicide molecule which is being introduced into a number of crop sectors.
“The inclusion of Arylex allows farmers to cover a wider spectrum of weeds while gaining a higher level of control.” Arylex is also present in Corteva’s autumn Belkar herbicide.
Mr Waite says this year is challenging for weed control. “A lot of oilseed rape has not had any herbicide. This is the ideal opportunity to use Korvetto and also to top up what has been done over winter because the wet soils and mild weather mean as soon as fertiliser is applied, the weeds will be off and away.
“Where Kerb and AstroKerb have been applied they’ve done a good job but certain crops are more open than normal, letting the light in and raising the potential for weed germination.”
While Korvetto will control some key weeds up to 15cm high, such as cleavers, this season, in very weedy situations where no herbicide has been applied and in open crops it will be an interesting challenge for the product in its first year, says Mr Waite.
In a normal rotation there are no following crop restrictions, however, should crops fail due to, for example, pigeon or CSFB damage after the new herbicide has been applied, the land can be re-drilled with following crops including spring OSR, barley, oats, linseed and maize but not legumes. Straw should not be used for composting, advises Mr Waite.
He says Galera will slowly be pulled out of the market but currently has an Extension of Authorisation for Minor Use (EAMU) on spring oilseed rape. “Korvetto does not have this yet so there will be a market for Galera for spring OSR for the time being.”
Korvetto is active in spring conditions, usually in temperatures of 7-8degC upwards, says Mr Waite. “It is a single application of 1l/ha. It is safe to the crop as long as you stay within growth stage parameters and is recommended at a water rate of 150-300l/ha with medium spray quality.”
Alongside providing independent agronomy advice, Sam Clarke also manages three farms on behalf of clients, which includes day-to-day running of the farms along with all purchasing and selling of inputs/crops. Clarke Farming Partnership also farms 400 hectares predominantly focused on sheep and pedigree beef production.
Mr Clarke is looking to use Korvetto this spring to control weeds in oilseed rape. “The main reason is that it has a slightly wider weed spectrum than Galera which we have used in the past. Korvetto is slightly stronger on cranesbill – up to 5cm and slightly better on cleaver control than Galera. It also brings in fumitory.”
Controlling weeds in oilseed rape and what to use has become a difficult judgment call with growers less certain about whether they will have a crop than in the past due to pests such as cabbage stem flea beetle.
Mr Clarke says: “We have dropped pre-ems altogether. This brings a saving of £15-£20/ha. Investing this amount in them is not wise as you can lose the crop before it reaches true leaf.”
This season has been a particularly trying one for growing oilseed rape, he says. “Crops are behind and there has been a double whammy from CSFB pressure and water-logging that has suffocated plants and stopped the luxury of autumn growth we are used to. Crops out there are also coming under pressure from pigeons. It has not been a good year for oilseed rape, full stop.”
Of OSR crops drilled that Mr Clarke advises on he says about 40% were lost – 35 percentage points to CSFB and 5 percentage points to water-logging and pigeon damage. “Of the 60% left, 20% was very good, 20% average to small and 20% small to concerning. In mid-February we will need to start N and herbicide programmes so we will be forced to make a decision about whether to run with these crops or not.
“In a normal year growers can control weeds to a good level but this year they are hesitant to spend lots of money on herbicide programmes. Generally, crops are slightly weedier out of design [growers investing less] rather than weed pressure.”
However, he says with activity on cleavers up to 15cm and cranesbill up to 5cm as well as fumitory Korvetto ‘has got to feature in herbicide programmes’. He adds that it will lend itself to sand land – traditional root growing land, but also have a place on heavy land for control of cranesbill and cleavers, in particular. “It won’t be used everywhere but will be a very useful addition.”