Crop Watch: Wet spell prompts slug warning for slow emerging wheat

Blackgrass control, slug activity and light leaf spot have been taxing agronomists this week.

While the dry autumn for some has hindered blackgrass control, one benefit is that it has kept a lid on diseases with wheat looking clean, says Iain Richards.

However, the wet spell in recent days has seen a rise in slug activity and combined with slow cereal emergence, there is a rising risk of damage warns Marcus Mann.

See also: Widespread pyrethroid resistance found in diamondback moths

Giles Simpson adds that mildew is now visible in some early-drilled winter barley. Mildew is also being seen in Yorkshire, along with frit fly, says Patrick Stephenson.

South: Iain Richards

Agrii (Hampshire)

Iain-RichardsOnce again, late wheat drilling is paying handsome blackgrass management dividends. But, with such a dry autumn, it’s been a matter of holding our nerve well into the second half of October. 

We didn’t drill our worst blackgrass fields until the last week of the month. This means these crops are only just coming through while our late-September drillings on lower risk ground are already well-tillered.

Thank heavens we held off as long as we did, though. It was mid-October before a lot of our blackgrass found sufficient moisture to grow and, even then, we only secured decent flushes to glyphosate-off where stubbles were moved and consolidated after harvest.

As a result, many crops going in before the 20th of the month in our area emerged with far too much weed growth. What’s more, the dryness got in the way of both pre-emergence activity and seed-bed consolidation.

So, seriously beefed-up pre-emergences with extra contact activity have been needed, really adding to the cost.

In contrast, where we got our cultivations right and waited for enough soil moisture, we were able to eliminate a good amount of blackgrass before drilling, achieve much better seed-to-soil contact and make the most of our pre-emergences.

Although these crops are well behind as temperatures drop away, there’s plenty of growth left in the sort of seasons we’re seeing these days.

Disease development

Thankfully, the dry autumn has kept the lid firmly on disease development. Even our earliest-sown wheats are going into the winter nice and clean.

Equally, we’ve been able to hold off on any oilseed rape fungicides well into November, employing combinations of prothioconazole + tebuconazole targeted primarily at early light leaf spot control with growth regulation, where necessary.

We’re not combining this with propyzamide, though. Instead, we’re waiting for soil temperatures to fall further and crops to lose enough leaf for the best persistency and soil coverage.

Interestingly, we’ve seen some significant patches of clubroot in our oilseed rape for the first time ever this autumn. Maybe the dry conditions have prevented our liming being as immediately effective as usual?

Or perhaps it’s a worrying sign for the future and we’ll need to be thinking more about resistant varieties?

East: Marcus Mann

Frontier (Essex)

Marcus-MannWe are now in a period where soils dry out very slowly and spray opportunities become few and far between. Travelling ability is dictated by crop, cultivations, local rainfall and field drainage. 

With cereals being generally drilled later into cooler soil, emergence has been much slower with crops generally taking three weeks to emerge. On heavy soils it is even longer.

Increased moisture has encouraged blackgrass germination, which has been sprayed off with a pre-emergence glyphosate. In earlier sown crops, blackgrass is still emerging and so are receiving contact graminicides, plus an additional residual, typically flufenacet.

The damp, cool soils should enhance the efficacy of the residuals. However, if using iodosulfuron + mesosulfuron mixed with a flufenacet product, be mindful of soil temperatures and ensure the blackgrass is growing when applying.

Where autumn germinating brome is being found in winter wheat, remember that earlier applications of pyroxsulam are more effective. Also ensure good coverage, as the small hairs on the leaf can affect the uptake of the product.

Slug risk

With slow emerging crops, vigilance is needed when it comes to slugs. Although pressure has not been as high as predicted, their activity is now rising as soils return to field capacity and with crops not emerging quickly, the risk of damage is higher.

Heavier patches of fields where the crop is struggling are, therefore, having slug treatments applied, subject to thresholds.

Aphids can still be found within crops and the plan is to apply an insecticide to manage the risk of further barley yellow dwarf virus infection. When going through the crop, we will also apply manganese.

Last year with a milder December and January combined with forward crops, manganese deficient areas became very apparent. This has allowed us to ensure these areas have had both foliar and seed treatments to help alleviate this.

Phoma is beginning to reach threshold in oilseed rape and where fungicides are due to be applied this will now be tank mixed with propyzamide. The soil temperatures and moisture deficit are now beginning to reach suitability for propyzamide.

Cabbage stem flea beetle adults remain active and these still have the potential to lay further eggs and produce more larval damage. Therefore, consider an insecticide when applying propyzamide.

West: Giles Simpson

Pearce Seeds (Somerset)

Giles-SimpsonI don’t think we could have had a better autumn for crop establishment and subsequent treatments.

The weather has certainly been on our side, lots of fine dry weather with rain coming at regular intervals. If we now had some colder weather then that would be ideal.

Oilseed rape crops look extremely well and have received a phoma fungicide (penthiopyrad + picoxystrobin) where thresholds have been reached. This should also give some light leaf spot control.

Boron has been added to the fungicide mix where tissue samples have shown a deficiency.

Wheat crops have emerged well and the pre-emergence sprays have done a good job, although some grassweeds are now appearing in places so a follow up spray has been applied.

An aphicide has been put in as there are a few aphids about and the early drilled Deter-treated (clothianidin) crops could be susceptible.

The later drilled wheat behind maize should be OK, as the seed treatment should still be effective. This is unlike last year where most of these were sprayed pre-emergence as well.

Slugs have only been appearing in some fields, mainly the wheat drilled behind grass. These have now had an application of either metaldehyde or ferric phosphate.

Mildew in barley

Early drilled barley crops now have small amounts of mildew appearing in them, so hopefully, some colder weather will be forecasted.

The grass leys that have been sown this autumn have received a herbicide to control broad-leaved weeds. In fact some of the August-sown crops have been grazed lightly by livestock, as the ground conditions allowed this without damaging the young grass.

Cover crops sown this autumn have also grown extremely well and will be mopping up any spare nutrients. There is a lot more interest in these crops even if not needed for greening, as farmers are seeing the benefits in improved soil structure and condition.

At a meeting last week, we saw a crop of mustard that stood 4ft tall only seven weeks after drilling.

North: Patrick Stephenson

AICC (Yorkshire)

patrick stephensonHaving talked to farmers from around the country, it certainly seems that our weather has once again been very variable. Rainfall, for my little patch, has been just about right for drilling and establishment.

Pre-emergence herbicides on the whole have worked well and we have been able to top up as required. Unfortunately, there have been casualties and we have chosen to destroy some crops and start again.

The choice to broaden the rotation using spring barley and grass is certainly the correct one for my part of the world.

Mildew can easily be found in wheat crops, along with an unusually high number of frit fly. These items are more of passing interest, as in the case of frit fly, we have no chemical treatments and mildew will die with the older leaves as winter takes hold.

Overall, the wheat crops look well and even the final drillings only just completed have gone into good seed-beds. Slugs have been noticeable by their absence, and it is a surprise that some metaldehyde spikes have been found in watercourses.

Oilseed rape area

The AHDB Early Bird Survey shows falls in the area of planted oilseed rape. This is no surprise considering the appalling performance last year, coupled with the problems of establishment and weed control.

This year’s crop is in rude health and many now are over the top of my wellies, a true scientific assessment of a forward crop. Propyzamide has been applied and fingers are crossed that control of blackgrass will be good.

Light leaf spot control still tests me, with the Scots deeming autumn treatments as a waste of time and the historic data showing positive yield responses.

I see leaf spot control playing a similar role to a T0 in wheat, but with better disease resistant varieties becoming available, then its true value could be in question.

Winter barley crops are well advanced and mildew is easily visible, but cooler weather, “the agronomist’s fatigue”, and sprayers being put to winter quarters will leave these crops to the weather.

This autumn would certainly lend support to the global warming theorists, who state that we now have an extra months growing season compared with the 1960s.

Online grain trading made easy with Farmers Weekly Graindex

It takes just a couple of minutes to create a listing on Farmers Weekly Graindex and you’ll get a range of prices to compare from active buyers who want your grain.
Visit Farmers Weekly Graindex