Clover safe spray on NI market this spring

A broad-spectrum clover-safe spray for use on established grassland and new sown leys, should be available to buy at local merchants in NI from 1 April 2025.

Brought to market by global chemical and seed company, Corteva Agriscience, ProClova XL has been on sale in the Republic of Ireland (ROI) since 2024 and offers control of the likes of docks, redshank, buttercup and chickweed.

The main active ingredient in ProClova is rinskor and it is one of two new actives for grassland developed by Corteva.

The second is arylex, which is being included in a new grassland spray known as ProGrass. That product will be available in Britain during 2025, but not yet in NI.

The chemistry toolkit has been decimated over decades

Speaking at a launch event for ProClova in Cookstown last Thursday, Robin Bentley from Corteva said getting regulatory approval for rinskor was “absolutely massive” for weed control on farms. Prior to that, it was back in 2006 that the last new active ingredient for grassland was successfully brought to market by the company, with the approval of aminopyralid, used in Forefront T. In the period since then, a number of other actives have dropped out.

“The chemistry toolkit has been decimated over decades. The market is not awash with new solutions. The toolkit is rather bare,” Bentley said.

Despite that, he said new products are coming through, including potentially a new clover-safe spray in 2026.

Co-pack

As well as rinskor, ProClova includes the proven active ingredient, amidosulfuron.

ProClova is sold in a co-pack alongside XL adjuvant, which is included to help break down the waxy surface of a leaf, helping to ensure the active ingredients are able to get into the plant. In the medium term, the plan is to formulate the adjuvant into ProClova.

The first year for ROI sales of ProClova in 2024 were strong, with 60% going for application to new sown leys and overall volumes matching the likes of Doxstar Pro and Forefront T, confirmed Bentley.

He said ProClova in NI will be priced somewhere between these products, but “possibly more closely to Doxstar Pro”.

For a new sown ley, the recommended dose rate is around two-thirds that of established grassland, so the price point is lower. A pack size including 250g of ProClova and 500ml of XL adjuvant, treats 3ha of new sown leys and 2ha of established grassland.

ProClova is not as robust as the likes of Forefront T, so it is important to follow label requirements, David Gurney from Corteva told last Thursday’s launch event.

Perhaps the key requirement is that the spray should only be applied when overnight temperatures are forecast to be above 8°C for a period of three days before and three days after application.

For new sown leys, ProClova is currently only approved for use between 1 April and 31 July, although Corteva is hopeful this period might be extended by a month. In established grassland (over 12 months old), it can be used between 1 March to 31 October. Established grassland can be sprayed every year, if necessary, but if the product is used on a new sown ley, the label currently requires that the field cannot be sprayed again with ProClova for two years.

“We are taking it up with CRD [UK Chemical Regulations Division], but it applies this year,” Gurney said.

ProClova is also not approved for use in clover-only swards or for red clover in the year of sowing.

Check

When spraying the product, the advice is to wait for clover to reach the three-trifoliate leaf stage. It is likely that the clover will suffer a growth check, but it will quickly recover, Gurney said.

He also emphasised the importance of ensuring weeds are actively growing and pointed out that ProClova will not deliver a rapid kill like that seen with Forefront T.

In practice, it might take six weeks to achieve the same level of kill seen with Forefront after 14 days.

“ProClova will deliver excellent broad-spectrum weed control, but it is significantly slower than other grassland products. We need to be patient while the product does its stuff,” Gurney said.

ProClova is not suited to multi-species swards (MSS) as the likes of plantain will not survive a treatment, Robin Bentley confirmed.

He said research and testing into potential products that could kill weeds in a MSS was “ongoing work”.

In practice, he said the approach often used by farmers is to clean up a sward with Forefront T, before sowing out in a MSS the following year.

In trial work done in spring reseeds established in 2021 and 2023, ProClova delivered “very good weed control” confirmed Teagasc grassland researcher, Dr Michael Egan.

“There was a slight decline in white clover initially, however, it was nothing to be worried about and was quickly rectified,” he told attendees at last Thursday’s launch event.

In the Republic of Ireland, he said there has been a significant shift towards spring reseeding for those looking to establish a new grass white clover sward. In that scenario, given the small size of clover seed, the key is not to sow it too deeply, Egan said.

The alternative is overseeding clover into an existing sward, however, the sward should have a high percentage of ryegrass and be relatively open. There must be adequate moisture in the soil and air temperatures of at least 8°C.

Irrespective of method of establishment, low indexes for phosphorus (P) or potassium (K) should be corrected and soil pH should be over 6.5.

“It is a waste of time and money if the criteria are not met,” Egan said.

He said the best time to sow clover is between 15 April and 15 May. Delaying beyond 15 May increases the risk of a soil moisture deficit impacting clover establishment.

Post-sowing

However, ultimately it is management in the three to four months post-sowing that will determine whether a persistent grass clover sward is established.

Clover needs sunlight, so regular light grazing is required to prevent it being out-competed by grass.

Over the first three months, clover goes through a rosette phase, during which it is reliant on a central taproot.

In the expansion phase, the plant expands along various branches, with the taproot starting to die off at around 12 months. That is followed by the clonal phase when the plant is actively fixing nitrogen.

“If there is not enough sun getting through, clover will try to grow up rather than develop a taproot,” Egan said. “There is a strong correlation between taproot size in the first three months and persistency.

“The first 12 months is so important. Where the clover is out of the sward after eight months, people blame everything but management,” he added.

For a grass white clover sward to deliver a significant lift in animal performance, there must be sufficient clover in the sward.

The aim should be to have 20% of the sward as clover by mid to late May.

“At around 20% you also get 100 to 120kg of nitrogen fixed per ha per year,” Egan said.

The interim results of on-farm research into red clover silage will be outlined at a webinar organised by AgriSearch, taking place at 8pm on Wednesday 5 March.

At the event, AFBI grassland researcher, Dr David Patterson, will discuss the results coming from the ZeroNsile project, which was established by AgriSearch in 2023 to examine the feasibility of producing silage without chemical nitrogen fertiliser. In total, 12 participating farmers across NI established red clover swards on their farms.

Two of those farmers (Andrew Crawford and Frank McDonnell) will discuss their experiences.

There will also be a presentation from CAFRE’s Robert Patterson on the work done at Greenmount to establish white clover in grazing swards.

To register for the webinar visit the AgriSearch website (www.argisearch.org).