Crop Watch: Rain forces change to herbicide programmes

While growers in the West are still to finish harvest and deal with severe ruts before the winter, growers in the North have managed more than 80% of drilling in certain areas, but are running out of “easy” land.

Generally, drills are still in the shed, and as the wet weather shows no signs of abating, our agronomists are advising increasing the seed rate, and potentially limiting the number of actives to prevent crop thinning when drilling does become possible.

Oilseed rape that has managed to come through cabbage stem flea beetle is now being savaged by slugs.

East: Marcus Mann


Agronomist Marcus Mann

Marcus Mann

After a very dry end to the summer, autumn has been “damper” than we are accustomed to in the East.

This has hampered drilling of winter cereals, with a vast amount yet to be done.

On the plus side, the recent rainfall has resulted in the first significant flush of blackgrass.

Ensure any emerged grassweeds are sprayed with glyphosate prior to drilling, as cultivations will not control it when soil conditions are as wet are they are currently.

See also: Organic grower turns to sheep to control weeds

Also ensure that when field conditions dry sufficiently to allow drilling to progress, that there is adequate time to return with the residual pre-emergence spray.

Seed rates will also need to be discussed as we move through October.

Towards the later part of the month, establishment will begin to decline and it would become advisable to increase from 350seeds/sq m to 400seeds/sq m in winter wheat.

Oilseed rape is a mixed bag depending on drilling date and how long after establishment it received enough moisture to germinate.

Crops that were slow to emerge have been affected by cabbage stem flea beetle, which in some areas has been severe.

Different methods have been trialled to try to mitigate the level of damage, including keeping neighbouring volunteer OSR as trap crops.

To date, the evidence suggests few approaches have been effective.

Crop nutrition does, however, appear to be key in giving the crop the best possible start, and in reality is of greater benefit than chasing the pest with multiple insecticide sprays.

The addition of Belkar (Halauxifen-methyl + picloram) has allowed a chance to ensure crop establishment before controlling broad-leaved weeds.

Belkar is used on two true leaves from 1 September to 31 December and provides useful contact activity on cleavers, poppy, cranesbill, fumitory, shepherds purse and cleavers.

Corteva have provided a useful online tool in which to monitor propyzamide timing for blackgrass control.

It helps to prevent early applications in conditions that will lead to a quicker breakdown and thus compromise control.

West: Giles Simpson

Pearce Seeds

Agronomist Giles Simpson

Giles Simpson

I will start with the positives of this summer’s harvest; many farms achieved their highest ever winter barley yields, and most harvested dry and with a good quality and yield of straw, which is very important in the South West.

The wheat harvest was a bit stop-start, but again yields were very good.

Spring barleys were average, but most made malting quality.

These crops didn’t tiller very well in the dry spring.

The negatives of this year’s harvest is that there is still 30-40% of the maize left to cut and plenty of harvested fields have some ruts in them.

Hopefully, it will dry out enough to lift these ruts before the winter sets in and some crops can be drilled into them.

The autumn cereal drilling campaign hasn’t really started due to more than 200mm of rain in the past three weeks.

I would estimate that, at best, 10% of the cereals are drilled and we can only hope for some dry weather soon.

As drilling is delayed, the seed rates will be stepped up.

Blackgrass generally isn’t a problem on the majority of ground destined for cereals, so I had planned to do a post-emergence weed control, aphicide and manganese all in one pass.

Now drilling has been delayed, this will change to a pre-emergence herbicide done as soon as anything is drilled, followed by an aphicide once the crop is up, if we can travel.

The loss of Deter (clothianidin) means that in reality most drilled crops won’t receive any aphid protection this autumn unless we get a prolonged dry spell. I’ll keep everything crossed.

The oilseed rape crops along with cover crops and stubble turnips have been hammered by flea beetle.

I fear that many will be written off even though many have been sprayed two or three times, and now the slugs are beginning to have a go.

If it does dry up, many will receive an application of pellets.

North: Patrick Stephenson

AICC (Yorks)

Agronomist Patrick Stephenson

Patrick Stephenson

Since the rain started, we have amassed more than 190 mm.

Things are moist and there is a sombre attitude setting in.

We have been drilling and many growers north of the Tyne will be more than 80% complete.

This contrasts widely compared to drilling south of York, where 40% complete is a victory.

All the “easy” land has been drilled, leaving the thorny question of how long do to keep trying to drill the rest?

In 2012, it became very clear that puddling in wheat was the worst possible option.

We still have all of October to carry on drilling remember; there is no right time, but there is a wrong time.

We should not tie ourselves to a calendar date, but experience tells me bonfire night is often a point of no return.

Crops drilled late need a good seed covering, particularly if robust pre-emergence herbicides are going to be applied.

It may be worth considering limiting the number of actives as crop thinning can occur with multiple actives.

Two weeks ago, slugs were an endangered species and David Attenburgh was being rolled out for a “save the slug” campaign.

Now slugs are lording it in the wet conditions, grazing is common, and with many seed-beds far from ideal, the risk of substantial damage is high.

I have a sneaking suspicion that our school calendar owes a lot to farming.

Each half term nearly always coincides with a period of essential farming activity.

Many people have failed to apply pre-emergence sprays and these fields need watching closely, and as half-term is looming, time to cancel the holiday.

If you can spray at peri or early post-emergence, then continue with the pre-em programme, subject to the label recommendations.

If the grassweeds are through and past the two leaves then a rethink is required.

Having found winged aphids in early drilled crops, then barley yellow dwarf virus (BYDV) is a threat.

The AHDB BYDV management tool is a useful guide, but remember the late-drilled crops are unlikely to require any aphicide.

Oilseed rape crops drilled early (first week in August) are now well established and away from adult flea beetle damage.

The crops drilled from Mid-August onwards tell a different story as the rain has certainly produced a flush of cotyledons, but will these survive?

With drilling proving difficult, the desire to pull up half fields of rapeseed has diminished.

How much crop have we lost? Very little north of Newcastle and maybe 40% south of Scotch Corner.

South: Stan Harrison


Stan Harrison

I had hoped for my first article to be reporting on a positive start to autumn drilling following a very good harvest.

However, the oilseed rape crops in the ground are suffering from poor establishment due to dry conditions at drilling, a more vigorous cabbage stem flea beetle population than before and once the rain started, slugs deciding to make an appearance.

Previously, we have managed flea beetle attacks with pyrethroid insecticides, which did enough to allow the crop to establish.

However, knowing how difficult a pest it is to control, this year we set out to maximise the efficacy of applications by reducing the hydrolysis of pyrethroids in our alkaline water.

We also asked operators to spray in the evening after dark, and added in various nutrients and stimulants to assist early crop development.

We have also been trialling the benefits of companion cropping on some fields.

Where grassweeds are not an issue, some wheat and barley crops have been drilled, and with the recent rains, we expect them to establish well.

For those who need stale seed-beds, the rain has at last brought on the germination of problematic grassweeds.

At least we can now apply glyphosate with confidence that it is a good investment in our overall strategy to control grassweeds.

For growers who have switched their approach to include more cultural methods, the pressure of high blackgrass populations has been reduced to much fewer fields and areas within fields.

Maintaining these levels of control still requires a pre-emergence loading of mixed residual actives on to good seed-beds along with close inspections to monitor results.

The loss of Deter adds to our establishment concerns.

First, it will lead to an increased risk from slugs (and wireworms), so it will be back to using the trowel to monitor germination and emergence.

For those with metaldehyde in stock, remember that 10m buffer zones should be left untreated or treated with ferric phosphate.

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