Five spring agronomy pointers

1. Was autumn grass-weed control successful?

With some earlier cereal drilling, unrolled seedbeds, late applications of pre-emergence herbicides, or eroded performance through warm soils and heavy autumn rains, autumn grass-weed control is likely to vary from field-to-field and across farms, despite good stale seedbed opportunities post-harvest.

“I anticipate some poorer control in places,” says Mr Astill. “But the only way to check is to walk and assess fields.”

Applying post-emergence sprays based on mesosulfuron, such as Pacifica Plus or Atlantis Star, may help, but to maximise performance these contact herbicides should be applied as soon as possible, to a dry leaf and ideally in bright sunlight.

“Equally, if pressure is too high, cut losses now and spray off with Roundup to give time for a spring crop, or an SFI option, if applicable, which could be better returning on marginal land.”

2. Have you set up a low- or high-pressure disease situation?

Drilling date and variety choice will have set, to some extent, the risk profile of wheat and barley crops this spring. Although spring weather has the greatest influence on what disease occurs, winter weather and nitrogen applications also play a role.

Early drilling increases Septoria risk, not least with warm seedbeds encouraging fast emergence, Mr Astill notes. “Those crops will have been exposed to pathogens for longer.”

A mild winter exacerbates diseases, including rusts, while a cold one reduces the threat.

“After you’ve applied early nitrogen in February, disease management is mostly about your approach to risk in terms of the weather.

“Be reactive to what it throws at us, but remember, the fundamentals of getting fungicide timing right to protect leaf layers won’t change.”

3. Are you investing more or less in your oilseed rape?

Now is the time to decide whether oilseed rape is going to make it.

“If you’ve applied first nitrogen doses, you’ve almost certainly made the decision to invest,” Mr Astill says.

“So keep monitoring for diseases such as light leaf spot, which, as temperatures increase, will begin to express its symptoms. An integrated approach to disease management is required - utilising varietal resistance is increasingly important and combining with fungicides is still beneficial. Remember fungicides work best as protectants.”

In April and May, use the AHDB Sclerotinia forecast tools during flowering to judge risk. Most crops benefit from at least one flowering spray, with products like Aviator effective against both diseases, as well as Alternaria.

4. Considering or growing maize?

With alternative break crops to oilseed rape of interest, Mr Astill highlights Bayer’s investment in its Dekalb maize portfolio.

The current varieties, DKC2684, DKC3218 and DKC3204, are all aimed for silage production for livestock feeding or biogas production, with FAO maturity ranging from 200-220.

“Where oilseed rape is no longer viable, maize provides a good opportunity to use later sowing dates and diversify weed control in the rotation.”

5. Need a new option for weed control in peas and beans?

With peas and beans now classified as major crops by the Chemicals Regulation Division (CRD), already depleted weed control options have been reduced further as extension of authorisations for minor use applications have been withdrawn, Mr Astill says.

“That means options based on straight pendimethalin and prosulfocarb can no longer be used.

“However, we do have a new authorisation for Emerger to be used pre-emergence in peas and beans, alongside a partner.

“Aclonifen is a novel mode of action in these crops, with good activity against cruciferous and Polygonum weeds, and some useful activity against grass-weeds.”

For more seasonal advice please visit our insights.

Tom Astill