Crop Watch: Large slug populations reported in cereal crops

Patience is in short supply for growers as the days slip by and rain continues to hamper work but our agronomists continue to urge caution about drilling into less-than-ideal conditions, with new Crop Watch contributor Ben Pledger warning a wet seed-bed will allow slugs free rein.

Crops already in the ground are struggling as well, with Neil Potts seeing evidence of slow emergence in parts after pre-emergence chemistry was washed down to seed depth when heavy rain blew in following spraying.

David Martindale strikes a positive note for growers in the North, saying that the wet weather has been useful in encouraging blackgrass to emerge in stale seed-beds and giving more time to control it.

See also: Healthy profit from spring oilseed rape despite poor season

However, this will only be effective if a proper effort is made to encourage the weed seeds to germinate, says Tod Hunnisett, saying growers need to go about it the same as if they were preparing for the actual crop.

East: Ben Pledger

ben pledger

Farmacy (Bedfordshire/Hertfordshire)

The memory of last year’s long, dry autumn has been replaced with the more recent images of land drains running in September.

Understandably growers are finding it difficult to delay drilling for much longer. Early drilled wheats are now emerging with blackgrass breaking the surface as well.

Farmers who can afford to be patient and delay drilling for another week in situations of high blackgrass pressure will see the benefit of allowing another flush to be sprayed off.

Patience will also be needed on land that was cultivated after the wet weather took hold where it is now nice and dry on top but still very wet at seed depth.

If this land isn’t allowed to dry further, drilling in a lot of situations will lay the seed in slots perfect for the free movement of slugs along the row.

Oilseed rape has fared a lot better this season, with most crops in the area growing away well from the adult cabbage stem flea beetle – one benefit the rain has brought us.

Sprays working well

We will now have to monitor crops in the spring for larvae in the stem of the plant. On the whole Centurion Max (clethodim) has worked well in sometimes higher than usual populations of blackgrass this autumn.

With most of it applied now, we start to focus on application timings of the first fungicide on the crop. 

Varieties such as Incentive, with lower phoma resistance, are now starting to possess decent amounts of lesions per plant.

This is earlier than usual, but was forecast. To protect against this, Plover (difenoconazole) will be applied in the next two weeks.

Where phoma is really taking hold, prothioconazole will be added to the mix for curative action. Early drilled, very forward crops will also benefit from an application of tebuconazole to take advantage of its growth regulatory effect.

North: David Martindale

david martindale


Arable Alliance (Yorkshire)

Three positives immediately leap out after one of the most prolonged wet spells which engulfed most of September – and they all relate to blackgrass. 

The first is that it has forced more wheat to be sown later than planned, which will no doubt help to reduce the blackgrass pressure in the crop itself. 

The second positive is that there has been plenty of moisture for blackgrass to emerge prior to drilling and be sprayed off with glyphosate. 

Finally, there has been good seed-bed moisture to maximise the performance of the pre-emergence herbicides.

So, the start of the blackgrass battle so far has gone well as long as the seed-bed has been good and was able to be rolled. 

Winter barley crops are typically at the 1-2 leaf stage and have emerged quickly. Some fields have been held up from being sown with barley due to wet wheat straw laid in the swath. 

The delays to winter barley sowing may have compromised some yield potential and by the time you are reading this if it has not yet been sown then it would be best to leave the seed in the bag and switch to Plan B. 

A major concern is that not all the pre-emergence herbicides for blackgrass control were able to be applied in time due to the weather meaning weaker peri-emergence herbicide mixes being applied instead.

Fungicide marches in

A consequence of the wet September is that phoma has appeared in oilseed rape crops much earlier with earlier sown crops and susceptible varieties having already reached threshold levels, so have been receiving a fungicide to prevent this early infection causing a lot of damage. 

The levels of phoma visible in crops has varied enormously depending on the varieties’ resistance rating to this disease. 

More resistant varieties have not yet reached threshold and perhaps may escape with one autumn fungicide application rather than two. 

A large flush of blackgrass is now present and applications of herbicides containing clethodim have been applied to try and control as much of this early flush as possible.

Lesions caused by leaf miner are very apparent this autumn but the damage often appears worse than it seems, with no requirement for a specific insecticide.

South: Tod Hunnisett

Tod Hunniset


AICC (Sussex)

It’s probably a good thing we can’t predict the future, because if we could many people would choose to get off the planet.

I ended my last Crop Watch (3 July) with the statement: “Waiting on what looks to be an early harvest, I do wonder what’s coming next.”

As of last Thursday (4 October) there was still wheat and spring barley waiting to be combined in Hampshire and Sussex.

The problem is that in my area, for about two months, we haven’t actually managed to go more than 48 hours without some rain falling.

Even last weekend, having been promised what looked like a reasonable spell, an unexpected shower on Friday evening was enough to frustrate the next day’s work.

The phrase “It must stop soon” is being frequently heard around the countryside, and it’s the opportunity-snatchers who are managing to keep going.

Get seed-beds sorted

The moisture has allowed a reasonable chit of weeds for pre-cultivation glyphosate. The message about consolidation is slowly getting through – there is no better demonstration than the parallel lines of blackgrass where a tractor has driven across a field that has been simply “lifted”.

A stale seed-bed is exactly what it says: a seedbed, designed to get seeds to germinate, as one would when sowing a crop.

My feeling is that a decent set of rolls is a highly valued and under-utilised cultivation tool.

The mild moist conditions have also allowed slugs to get back up to strength. If you see large areas of rape stubbles clean of volunteers then the chances are it’s not down to wonderful combine settings but a high slug population.

Fortunately it seems the metaldehyde message is getting through too; more people are opting for ferric phosphate as a replacement or a follow-up.

A bit like the “Drink Aware” campaign – “Metaldehyde Aware” just enters the consciousness. It might prolong the availability of this very useful active.

West: Neil Potts

Neil Potts

Matford Arable (Devon)

The weather has been simply awful through August and September and has turned what looked like a quite promising harvest into a nightmare of trying to grab wet crops whenever there was half a combining opportunity.

The upshot of a late harvest is that the drilling of the next season’s crops is now behind schedule, with the most forward of these being winter barley and these only just emerging, so very little to report on as yet, beyond having received a programmed pre-emergence application.

The winter oilseed rape crops generally went in on time as the winter barley was cut ahead of the downpour in August.

The wet weather has meant that slugs have been a fairly major problem and been difficult to control, causing severe thinning in some crops.

There have also been some instances where heavy rain after pre-emergence sprays were applied has washed the actives down through the soil and has resulted in slow crop emergence.

Promising maize harvest

The maize harvest is in full swing at the time of writing. This is one crop that appears to have really enjoyed the season so far with some very big yields being reported.

The cobs are generally very mature but the crop is still pretty green as there is plenty of moisture in the soil to keep the water content of the plants high; yields away from exposed coastlines yields are 49t/ha, plus or minus a little.

Once again, the earlier drilled crops are, on the whole, doing better than the later drilled ones and they have, as would be expected, reached maturity earlier as well.

Fodder beet crops are also looking like they will produce some monstrous yields this year, with many crops having a bigger yield underneath them in July than was achieved at harvest last year.

Hopefully by the next time I report, we will have caught up with autumn drilling and everything will be back on track.

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