Crop Watch: Frosts and drought hit crop potential

Frosts last week have had an impact on crops with Richard Harding reporting winter beans with some stems breaking in the South.

The cooler temperatures have also slowed crop development and Marion Self warns that this may stretch to a three-week gap between T1 and T2, prompting the need for a T1.5 in some crops.

In the West, Antony Wade the variable weather has led to strange barley growth, which is making growth regulation a challenge.

See also: Ramularia resistance found in German barley

Finally in Scotland, Mary Munro reports rising disease pressure despite the lack of rain, with a lot of septoria in lower leaves and yellow rust evident, particularly in the Lothians and Borders.

North: Mary Munro

Mary Munro

Mary Munro

AICC/Strutt and Parker (Perthshire)

In Scotland, we nearly always have a day or two of foul weather at the end of April. One poetic name for it is the “Teuchat storm” because it comes at the time the lapwings (or teuchats) are nesting.

Unfortunately, it is not a poetic experience if you are a lapwing or are lambing at the time. However, it often provides a watering for crops, but this year the storm was a late fall of snow that lasted a couple of days and did nothing to relieve the current moisture stress.

It washed in some fertiliser prills that had been sitting on the surface, and some fields are looking greener as a result. I am always reluctant to wish for rain though, as it never knows when to stop.

Winter wheats are still all over the place in terms of growth stages. The more advanced crops have had T1s and are well into growth stage 32, but others are much later and just hitting GS31.

Rising disease pressure

Disease pressure is mounting and despite the lack of rain, there is a lot of septoria in lower leaves, and yellow rust evident, particularly in the Lothians and Borders, so sitting back is not an option.

Going early with T1 leads to a dilemma with T2, and the risk of leaf 2 being unprotected, but I would deal with the known risk now. A shot of pyraclostrobin is useful armoury against rust.

Winter oilseed rape is well ahead of last year, in full flower close to two weeks earlier than 2016. The rape crops look to have good yield potential this season.

Spring barleys have established well where there is a reasonable depth of soil and a good seed-bed, but where the soil is thin and on the brae faces the crops have been very slow to emerge.

Dry weather restricts weed development too, of course, and we have not had much warmth either. At least the crops will be developing good root systems.

West: Antony Wade

antony wade

Antony Wade

AICC (Herefordshire/Shropshire)

As I sit writing this article on the Sunday before May Day bank holiday I, like many farmers and agronomists are wishing that it will be a typical wet and miserable British bank holiday because even in the West, we are in desperate need for some rain.

A paltry 15mm has fallen in April when a more normal amount would be over 50mm. Winter crops are starting to adversely respond to this lack of moisture, although it is notable that farms and fields that have regular organic amendments and, therefore, better organic matter levels are holding out much better.

Wheat that was well tillered has lost lower leaves and more worryingly tillers, as it has not been able to get hold of nitrogen applied over the last month due to the dry conditions.

The dry weather should have eased the septoria pressure, but lesions were still easily found on the tips of leaf four when writing T1 recommendations.

So an SDHI/azole co-formulation plus chlorothalonil was deployed on all of mine except some later drilled Costello after maize, which had a robust dose of prothioconazole + chorothalonil.

Strange barley growth

Barley crops have reacted strangely this spring. They were slow to get going hence T0s were delayed or cancelled. T1s went on only just ahead of the wheats, but have romped on recently.

This growth pattern has made growth regulator strategy challenging. What we have applied so far looks to have controlled height quite well, but the concern is that once we get some rain, they will “bounce”. Getting a late PGR on before the ears emerge is going to be a struggle.

Disease levels are generally low, but there is an amount of “abiotic spotting” which some have put down to drought stress, but I am not convinced this is the cause as some of my wettest fields are showing these symptoms. Reports of ramularia insensitivity to SDHIs will mean inclusion of a multisite with the T2.

Oats are a notorious crop for showing above ground any limitations below ground, such as moisture or nutrition. This is evident this spring with drain lines and ex muck heaps showing significant growth differences in some fields.

While there are some concerns about the winter cereals due to the lack of rain, oilseed rape crops look to have terrific potential, even those crops that we lost patches to clubroot have filled in quite well.

East: Marion Self

marion self

Marion Self

Prime Agriculture (Suffolk)

Dry conditions continue with no significant rain forecast. During April rain fall across the Anglia region was less than a third of the average and as showers have been localised some farms have received less than 5mm.

Temperatures are set to improve and crops are “ready to grow” if we could just have some rain, please.

Crops on lighter, gravely soils or where soil structure is poor are struggling whereas crops on heavier soils are holding their own.

Decision-making requires serious contemplation, but we remain focused on return on investment and achieving the crop’s full potential. We are mindful that applications should be robust for the weather we’re going to get, as well as what has been.

Moisture is still available at depth and recent light showers have melted nitrogen into the soil and should aid uptake of all nutrients – which have been poor in dry conditions.

Sugar beet

In sugar beet, herbicide programmes in more forward and uniform crops are well under way and working well. Where sprays were delayed due to hard frosts, control of difficult weeds is concerning and hardened, problem weeds will need close attention.

All spring crops with high blackgrass populations should be treated soon although performance of graminicides will be better in more moist conditions.

In wheat, septoria infection reflects their Recommended List rating with clear differences between varieties. On susceptible varieties yellow rust remains high and mildew pressure continues to develop, particularly in later drilled and stressed crops.

Cool temperatures have slowed crop development and the three-week gap between T1 and T2 (flag leaf emergence) could become stretched in more forward crops.

In these situations a T1.5 spray should be considered, but the necessity of this spray will depend on varietal susceptibility to rust and septoria, closeness of flag leaf emergence and weather. These sprays will be limited and where appropriate fungicide will be drawn from the planned T2.

South: Richard Harding

Richard Harding

Richard Harding

Procam (Sussex)

The dry weather continues here in the South with spring wheat being irrigated in Kent by those lucky enough to have the means, indicative of just how dry conditions were getting last week.

Frosts last week have had an impact on winter beans with some stems breaking. There is also an increased chance of missing pod sites on oilseed rape racemes where crops were caught in full flower.

Winter barley has just started coming into ear with crops now at or even beyond their T2 fungicide timing of prothioconazole and trifloxystrobin plus chlorothalonil. Mildew has been very common in cereals this spring requiring a specific mildewicide in some circumstances.

The decision to apply a late plant growth regulator has been difficult in the cool and dry conditions albeit for the most forward of unstressed crops. The majority of T1 wheat sprays have now been completed with some crops not far off their T2 application.

Septoria threat

Even the light showers we have been having will be doing enough to maintain the septoria threat and mean that there is no room for complacency with fungicide selection.

Building on a robust T1 of isoxapyram plus epoxiconazole, the plan will be to follow up with a robust mix of actives – one of the new SDHIs for this year benzovindiflupyr in combination with prothioconazole, azoxystrobin and CTL to aid resistance management.

The alternative is to consider fluopyram in mixture with bixafen and prothio, perhaps if one hasn’t used the latter two actives at T1.

The more forward oilseed rape crops are now past peak flower and beginning to show green again. Last week’s sclerotinia risk report is still relatively low aided by the dryness and cold.

However, where rain has fallen and petals are sticking to leaves infection cannot be completely ruled out and a second fungicide spay is planned to maintain protection for the remainder of the flowering period.

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