Issues with clover-safe sprays are continuing to present problems for farmers. Clover-safe sprays are generally referred to as sprays that kill weeds but not clover in new reseeds. Up to this year, the only active ingredient approved as a clover-safe spray in new reseeds was 2,4-DB and MCPA, commonly referred to by the brand names Clovermax, Undersown or DB Plus.

When the registration for these products ran out, they could only be used under an emergency use licence and that has been the case for the last few years. With the launch of the new clover-safe spray Pro Clova earlier this year which has a different active ingredient, it was presumed that the emergency use for the 2,4-DB products would no longer be required.

However, that is not the case and 2,4-DB-based products are now available under an emergency use authorisation to Irish farmers once again, but this time are only available for use on red clover swards. This is because Pro Clova is not approved for red clover swards in the year they are sown. It can be sprayed on them in the second growing season, but for perennial weeds like docks, that’s probably too late if one wants to get a good kill.

This authorises the use of CloverMax and DB Plus sprays for sale and use on farms as an emergency use from 15 June to 15 October 2024. During this 120-days window the spray can only be applied to newly sown reseeds with red clover sown at establishment.

PCS number

Farmers should be aware that a new pesticide control service (PCS) number is issued for each emergency use period and that only products with the correct PCS number should be used within the period that the emergency use is granted. The authorisation states that all unused products at the end of the approved period must be returned to merchants and distributors.

The issues with spraying red clover in reseeds are not going away so we will be back to the same position next year with a new emergency use of 2,4-DB for use on red clover likely. This will have to continue indefinitely unless new chemistry comes to the market.

Alternatively, 2,4-DB could be re-registered for use and there are some indications that this could happen.

Efficacy

In terms of the efficacy of Pro-Clova, some farmers are reporting that it is not as effective on thistles as 2,4-DB but that it does a good job on seedling docks. Indeed, thistles are not one of the weeds that are listed on the label as being susceptible to Pro-Clova.

Advice

The advice for both red and white clover reseeds is to spray for weeds at the six-week stage post sowing with a clover-safe herbicide.

This means that the seedling docks will be killed at the correct stage and the clover will be strong enough to withstand the effects of the spray.

Delaying spraying until all clover plants are at the three-week trifoliate stage usually means docks are gone too strong and will be harder to kill.

Spraying in good growing conditions will mean the clover bounces back quickly from the spray.