Crop Watch: Rain fuels weed growth and raises blight risk

Spring crops are seeing the greatest benefit from the recent rains, but some on heavier ground in the South West are looking patchy.

Rain has also sparked the arrival of a host of weeds, plus conditions have triggered blight sprays in potatoes.

Thoughts in the North are now turning to the T3 spray in wheat, targeting fusarium and topping up overall disease control where needed.

See also: How this arable farm became carbon negative and cut costs

North: Patrick Stephenson

AICC (Yorkshire)

The Formula One season is now well under way, but I challenge all the drivers to beat the speed with which wheat flag leaves appeared this year.

Having convinced myself that flag leaf timings would be seven to 10 days away, I was suddenly confronted by wheat crops with ears emerging.

OK, it was not all crops, and agronomists are prone to exaggerating, but it was nevertheless surprising.

Added to this we had the social media frenzy of sprayer tanks dissolving and mass panic has led to a very exciting week or two.

The most important factor has been the arrival of rain – I would go as far as to call it “golden rain”.

Although it arrived just in time to help develop good yield potential, unfortunately some areas in the South are still woefully short of moisture.

Sadly, the joy of watching the crops race through growth stages is soon over as all the detritus in the fields also comes to the party.

Blackgrass, ryegrass, bromes, sow thistles and a selection of half-dead broad-leaved weeds all start to peep above the canopy.

This great show of biodiversity may be appreciated by Chris Packham et al, but sadly not me.

Flag leaf sprays have now been completed on most crops and with the change to unsettled weather, we will have a true test of the new chemistry.

T3 fungicides in wheat bring much discussion, and it is certainly very important in the North. If people are targeting fusarium, the optimum timing is the start of flowering, which will only be 10-14 days after T2.

I think for most growers the main reason for T3 is to top up overall disease control and, as such, 21days after T2 will be a better target.

Early reports of orange blossom midge is not welcome news and, once again, we can only bemoan the lack of chemistry we have available.

Spring barley

The rain for the winter crops was very welcome, but for the spring barley it was essential. Nitrogen has at long last been taken up and everything has turned to a healthier colour.

Forward crops are approaching flag leaf and will receive a growth regulator for brackling and a fungicide. Later crops will be monitored and treated with a single fungicide later.

The oilseed rape crops have finished flowering and the gate is shut until desiccation time. There has been much discussion on the use of pod sealants.

This has revolved around questions on whether they are effective and when to apply them.

In many cases, they will not be required. A grower whose varieties have pod shatter resistance and are being grown in sheltered area is unlikely to see any benefit in a “normal” season, but an exposed site and large crop area would certainly have a much greater risk and, hence, managing risk with a sealant is prudent.

This, of course, then leads onto crop insurance. In the days of swathing this was often a common practice, but in recent years many growers have deemed it as non-essential.

However, with new-crop prices still high, many will be reassessing the need for it.

Winter beans are now well into flowering and have received their first fungicide. As pods start to set, we have a discussion over bruchid beetles and their control.

This, thankfully, is now very brief, as we accept that the chemistry available is at best poor and the damage to predators is likely to be more negative.

South: Oliver Bennetts

Zantra (Kent)

I am writing this article having been blessed with some much needed rain in the South East after a storm earlier in the week.

Wheat crops, with ears beginning to emerge, were really starting to show drought stress on thinner soils, but have now had nearly an inch of rain.

Wheat T2s have been going on over the past week or so, hitting the flag leaf to protect against rust and septoria. This leaves just the T3s to go as flowering begins.

Winter OSR has finished flowering and, compared with the past few years, crops look strong. This will, hopefully, mean customers stand a chance to benefit from the higher prices.

Beans are starting to flower and I’m seeing only moderate levels of downy mildew, but fungicides are being applied to guard against rust and chocolate spot.

Dry soils

Spring crops are really moving well, even with the dry soils, and flag leaves are emerging.

These crops are looking well and with the recent rain they will be racing though their final growth stages and ears will be out before we know it.

Fungicides are ready to go on with a dose of azole and strobilurin to keep a lid on late diseases.

While the rain has been a boon for combinable crops, it is starting to become an issue for others.

Some early potatoes are starting to meet in the row and have been hitting the Hutton criteria of two days above 10C and high humidity here in the South.

This means they will be getting their first blight spray in the next week.

I have also noticed that there has been an increase in aphid numbers, not only in potatoes, but other crops as well.

Aphids can be a serious problem for potatoes, with aphids carrying viruses such as leaf roll and virus Y, which can cause serious yield losses.

This is why keeping control of them in the early stages is very important.

If levels grow, a dose of acetamiprid could be mixed with the blight fungicide.

As we move to the later stages of the season, planning for next year and discussions about variety choice and agronomic challenges will start.

This year has gone so quickly – we need to be ready for what happens next.

East: Marcus Mann

Frontier (Essex)

Finally, some much needed rain has been received across the east of the UK and, with the outlook looking more unsettled, hopefully this will be sufficient to turn around some of the crops that were beginning to show signs of stress, and move them quickly through their final growth stages.

Septoria has been present in the base of most crop canopies for much of the season and, while it has been dry, one lesson we learned from the 2021 season was that the physical transmission of inoculum to high leaf layers can be significant.

On the back of this, given the recent rainfall and the increase in commodity prices, well-timed T2 sprays have been based on “innovation” chemistry to protect the key yield-forming parts of the canopy.

Given how quickly certain varieties have moved to ear emergence, these crops may reach flowering earlier than expected.

If the unsettled weather remains, the timings for the T3 applications at pre-/early flowering to protect for fusarium may be earlier this year. This will be particularly important for the quality wheats.

Leaf tissue analysis and nitrogen testing results suggest that even though it has been dry, the nitrogen appears to have been used well within the crop at this stage.

Biomass accumulation will have been helped by the recent rain, but there is still a long way to go.

Let’s keep our fingers crossed for more rain and plenty of sunshine throughout the rest of the season.

Milling wheat

For milling wheats it is now important to assess whether what has already been applied will be adequate to support yield potential and still reach 13% protein.

If the recent weather has improved crop potential, applying a foliar spray to the ear may be necessary.

Winter OSR is podding up well and look to have good potential.

With crops that are noticeably taller this year and considering the high value of the crop, going through with a pod sealant earlier to protect from storm damage will be important.

Timed ahead of the desiccant, this will also help prevent any shattering in the tramlines later on.

Winter beans are beginning to pod and look to have great potential. With recent showery conditions and thicker crops, the risk of chocolate spot is greater and will need to be carefully monitored.

Also be mindful of downy mildew, which remains in crops, and if conditions turn cool and humid, this may require the addition of metalaxyl.

The recent hot spell was followed by a large increase in aphid populations – in particular, pea aphids in peas, peach potato aphids in sugar beet and black bean aphids in winter field beans.

Follow-up applications will shortly be required in sugar beet. Teppeki (flonicamid) will be the product of choice to avoid affecting the beneficiaries within the field.

West: Giles Simpson

Pearce Seeds (Somerset)

With many crops that hadn’t fully germinated, the recent rain has been a relief. The only problem will be that there are different growth stages across fields, especially in spring barley.

Many fields had been looking pretty patchy, but should now all green up.

The spring crops drilled on the better ground have been fine. It’s the crops drilled on the heavier clay ground that were struggling.

The seed-beds were less than ideal in some situations and seed was not drilled into moisture.

This could be said for quite a bit of maize as well.

This always surprises me, as there is no excuse now that most maize drills can place seed well over 100mm deep, which would have put the seed into moisture.

It’s purely down to poor seed-bed preparation and then sub-standard drilling.

I get fed up with saying seeds won’t germinate if not drilled into moisture. Rant over for another year.

Most maize is now up and away, with many later-drilled crops up in rows within five to seven days. With the moisture I am already seeing rapid weed germination.

Maize weeds

The pre-emergence sprays seem to have done their job effectively, other than after a field that had a cover crop over winter, where the pre-emergence has done nothing for the fodder radish and mustard.

This field has now been sprayed to put it right.

My standard maize herbicide will be a mix of nicosulfuron + mesatrione + pyridate at various rates according to weed presence and size.

In places where docks are a problem on dairy farms fluroxpyr will be used very early on its own to deal with seedlings.

The winter barleys are all finished now and generally look well. We now just have to wait until the combines roll to see how they yield.

The winter wheats have septoria and yellow rust rumbling in the bottom of the crop. On a couple of fields the yellow rust has been a problem.

This is either due to variety or rain showers after the crop was last sprayed, but these have now been dealt with. Hopefully, when you read this, all the recommendations will have been applied.

The time is now upon us to start looking at next season’s cropping.

There will be plenty of discussions, I am sure, over the next few weeks around the kitchen table about forward cereal price and fertiliser availability and pricing.

All I will say is that every customer will have different circumstances, so it will be an interesting few weeks ahead. Oh well, at least I don’t have much hair to begin with.

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