Crop Watch: Blossom midge threat low as conditions stay dry

Worries about both orange and yellow blossom wheat midge have largely evaporated as the little rain experienced in the past week has not been enough to trigger a hatch, while wheat crops are largely through the danger period.

Spring barley has received its T2s after motoring through its growth stages, but drought stress is a real concern.

However, a period of wet weather in the North could be a problem for tall barley crops, showing the value of a good plant growth regulator programme.

See also: Why herbal leys have been added to arable rotation trial

Agronomist Helen Brown

Helen Brown

North: Helen Brown

Hutchinsons (Cumbria)

Just as we were starting to shout for rain up in Cumbria, our usual weather patterns returned. We have now had a few very wet weeks, causing some quick growth in all crops, and are hoping the rain knows how to stop again.

Winter cereals are now all out in ear and the last of the T3 fungicides are being applied in winter wheat.

In general, winter wheat and barley are looking well and the gates are being shut until harvest time.

There are tall barley crops around the county and any heavy storms will be a concern for some crops.

However, as shown at our trials site, which has plots treated with fungicide and plant growth regulator (PGR) alongside untreated ones, a good PGR programme has helped significantly thicken straw, making them much more resilient to lodging pressure without big reductions in straw yield.

Rhynosporium

Spring barleys are motoring through the growth stages after the recent wet weather.

Although weed control was done early in some spring barleys, most fields had poor weed emergence until recent rains, so weed control was delayed and applied alongside the T1 fungicide and PGR.

Both have now been applied on most spring cereals, except a few late-drilled crops.

As typical for the region, rhyncosporium is now present in spring barley, and prothioconazole has been the base of my fungicide choices in the crop, alongside an SDHI in higher-risk situations – for example, on less-resistant varieties.

The first blight sprays have been applied to potato crops after the first Hutton period was reached on 31 May.

Potatoes have benefited greatly from receiving some moisture and the first new potatoes are starting to be lifted in the region.

Maize is now through the film and any post-emergence herbicides required are being applied. Generally, this is where recent rains have encouraged a later emergence of weeds.

Sean Sparling

Sean Sparling

East: Sean Sparling

AICC/SAS Agronomy (Lincolnshire)

There has been 26mm of rain since my last report – now 148.6mm this year. Worryingly, we have had more than that in June in previous years, so those asking for rain should be careful what they wish for.

Winter barley spraying is complete, although there are concerns about just how frothy some of these crops are growing in the face of potential wind and rain.

Flowering is just getting under way in most wheat fields (another year has gone by without orange wheat blossom midge causing undue stress to either me or the emerging ears), but with an unsettled forecast, frequent light showers increase the need for a fusarium ear blight (FEB) fungicide.

Prothioconazole, tebuconazole and metconazole are pretty similar in their FEB abilities, so timing is crucial.

We must accept that even with a perfectly timed fungicide, it offers 50% control at best. So, once the ear is out of the boot, if wet weather coincides with those first anthers, you have about 12 hours to get the job right – miss that timing and the fusarium boat has sailed.

Drought stress

Spring barley T2 fungicide are now all on and spring wheat T2 fungicides are being applied to relatively clean crops in general, with everything crossed that the lack of rain may be less damaging as a result of the lack of heat.

However, it’s drought stress – not disease – that seems to have caused most leaf loss.

We now need rain, coupled with prolonged sunshine, to ensure crops have a chance of finishing properly. With sugar beet covering 90% of the ground, the dreaded Myzus persicae have appeared.

In our first season without neonicotinoids, those of us holding fire until one nymph for every four plants materialised were going really well – until last week, when it all changed.

The BBRO website is a help, but nymph levels in the field seemed to contradict their reassuring findings.

Peas and beans are now flowering and first fungicides are being applied. Bruchid eggs have been found on developing winter beans and downy mildew levels are increasing in the spring crop.

Linseed is showing the worst of the effects of drought on lighter and chalkier soils.

For those saying it has been a low-disease year, look at any missed strips and you will realise what a load of nonsense that is – fungicides have done their job this season.

Iain Richards

Iain Richards

South: Iain Richards

Agrii (Oxfordshire)

The wheats on our gravels are really suffering from lack of moisture, looking decidedly pale, with leaves completely rolled.

Although most of our ground has had barely 6mm of rain in the past four weeks, the rest of the crops are holding up well, mainly because the dry winter and spring has ensured such good rooting to depth.

The dry and settled conditions have meant we have been able to keep well on top of disease levels in general, and septoria in particular, with well-timed spray programmes through to the T3s just going on to our southern-most wheats as they start flowering.

We have yet to see any yellow rust, and the solatenol-based T2s we used on varieties with a clear brown rust weakness have done a good job.

With Agrii trials showing more than three-quarters of the most widely grown varieties are worryingly susceptible to brown rust, we continue to be concerned on this front wherever solatenol wasn’t included at T2.

Varieties such as Graham, for instance, which so many have valued for its disease strength, really only score little more than a 4 for brown rust resistance these days.

In these cases, we’re looking to the prothioconazole + tebuconazole co-formulation we are using at T3 for some useful extra activity.

OSR desiccation

Our earlier worries over blossom midge – both orange and yellow – have largely evaporated, as there hasn’t been enough rain to trigger much of a hatch.

Even if we get the rain we really need in the coming week or so, it looks like most of our wheats will be through the danger period.

Their real danger, though, lies in the sort of drought stress likely throughout flowering if we continue to miss out on meaningful rain. 

If it stays as dry as it has been, we are definitely going to need to hold off on OSR desiccation for as long as possible to secure yields and oil contents this season. 

Dare I suggest that avoiding desiccation altogether and relying on natural ripening may be something to consider?

After all, many growers in other parts of Europe do this very successfully, harvesting their wheats and earlier-drilled spring barleys first.

Speaking of which, our spring barleys have been romping along, with awns emerging on the earlier drillings and flag leaves fully out on later ones.

Many have gone from growth stage 31 to 39 in less than 14 days. Although disease levels are generally well contained, with a larger crop area and growing resistance to triazoles, we’re taking no chances with ramularia, using a combination of triazole, SDHI and chlorthalonil at T2 in most cases.

Stephen Harrison

Stephen Harrison

West: Stephen Harrison

Avon (AICC/Southwest Agronomy)

Grassweeds in cereals continue to dominate thinking as we move into the last few weeks of the current crop’s life. 

Bare patches are now appearing where crops have been sprayed off or mown – particularly in oats and barley, where effective control measures are limited. This is despite employing all available cultural control measures. 

Where crops have been mown off, please cut again after one month to eliminate regrowth. 

It is now too late to prevent viable seed return in areas of blackgrass not already destroyed.  Rye brome continues to pop up, often in fields where it has not been seen before. 

These spring bromus species are a real headache, as they often occur along with blackgrass and sterile brome, which are best controlled in the autumn, leaving no legitimate contact materials for the spring. Where practical, these weeds should be hand-rogued.

Blackgrass in crop

© Tim Scrivener

Septoria and rust

Disease levels in cereals remain low, but after the recent rain and anticipated rise in temperatures, septoria will flare up in poorly protected crops. 

This illustrates the total folly of applying suboptimal flag leaf sprays to wheat, because the weather just happens to be dry at the time.  We currently don’t have accurate six-week forecasts.

Yellow rust is still appearing in spray misses in all manner of varieties, not just the usual suspects. 

Please forward leaf samples to the UK Cereal Pathogen Virulence Survey.  It is vitally important that any new races are monitored.

Wheat crops are now heading towards mid-flowering and are past the orange wheat blossom midge danger time. 

Cereal aphid levels remain low, while ladybird numbers are high. A most satisfactory combination. 

The wet weather of the past few days has meant some crops will receive their ear spray beyond the appropriate early flowering time for fusarium control.

Oilseed rape crops are just starting to change colour, so the countdown to harvest 2019 has well and truly started.

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