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Crop Advice & Expertise

How to protect crop yields in Scotland this May

Craig Simpson provides five nuggets for Scottish growers on how to control disease in combinable crops this May.

Crop Progress

As we head towards the last week of April as this is written, it has been dry and cold. Crops are not droughting out yet, but do need a drink. As soon as we do get a bit of rain, fertiliser will be taken up and crops will start moving.

Disease levels are pretty low, and the frosts have helped reduce yellow rust. But if it stays dry, without the frosts, I do think we will see more yellow rust developing.

Most T0s have gone on, with most T1s due either at the end of April or beginning of May.

Early drilled spring barley is through and looking decent so far; later drilled crops are sitting in dry seedbeds and could do with some moisture.


Craig’s agronomy tips for May

1. Dissect wheat crops to get T1 timing correct

With the unusually dry conditions in Scotland, nodal growth stages and leaf emergence are not easy to judge, so it is important to dissect plants to correctly identify which leaves have emerged.

For T1 timing to be spot on, you’re looking for final leaf three to be fully emerged. Go too early and you risk hitting leaf four and leaving leaf three exposed and potentially creating too long a gap to T2 for the fungicide to protect. Go too late and infection might have already occurred on leaf three, which will be difficult to control.

This season with the dry weather it is probably better to be a bit too late than too early, while watching the weather forecast to make sure you can get around before any rain arrives.

Yellow rust is the biggest threat currently, particularly with most arable areas in Scotland being coastal. Eyespot is another disease growers should be looking to control at T1, because there are some quite susceptible varieties grown in Scotland. If rain comes, Septoria will become a bigger challenge.

So you’re looking for products that can cover all three of those, which is where Ascra (bixafen + fluopyram + prothioconazole) fits well. Depending on risk rates could be 1.0 – 1.2 L/ha at T1.


2. Use Ascra’s rate flexibility to tailor to risk at T2

Assuming we do get some rain in the next month – it is Scotland after all – Septoria is likely to be the main disease driver at flag leaf timing, which is likely towards the end of the month.

Ascra fits nicely at this timing this year. Obviously writing this now it is impossible to know how much rain we will have, but the dual SDHIs of bixafen and fluopyram perform well against Septoria.

In most crops drilled in the last week of September or early October Ascra at 1.2 L/ha will give good protection.

If it does stay dry there is some rate flexibility with Ascra to reduce dose down to 1.0 L/ha, especially on more resistant varieties, such as Extase. But in reality, there isn’t a huge amount of those varieties grown in Scotland, with Group 4s such as Skyscraper and Spotlight more popular, which are weaker against Septoria.


3. Keep winter barley crops healthy to reduce risk from Ramularia

With T2 sprays in mind for winter barley, keeping plants healthy and free from disease and stress will help reduce the risk from Ramularia. Currently, there is a bit of Rhynchosporium kicking around and keep aware of net blotch.

Siltra (bixafen + prothioconazole) at around 0.4 L/ha makes for a good all-round base for an awns emerging spray (GS45), and provides timing flexibility if sprays are delayed. While resistance issues affect activity of SDHIs and azoles against Ramularia, trials suggest there is still activity against the disease from azoles, in particular.

For resistance management, it is helpful to add a multi-site so folpet is an option to add to Siltra, but just be aware it is not as effective as chlorothalonil, although it will provide some activity against Ramularia.


4. Protect spring barley crops from disease

Early drilled spring barley crops will usually have two disease control sprays but if it stays dry, in later drilled crops some growers might choose to only apply one spray depending on the disease levels present in the crop.

The first spray should be targeted at end of tillering, while the second, or only spray if you’re just going once, is as the awns emerge. Unlike in winter barley where the first spray is more important, in spring barley it is the second spray which drives yield.

As in winter barley, Siltra is a good option for both timings at a slightly lower dose of 0.4 L/ha.


5. Check for light leaf spot in oilseed rape

Very few oilseed rape crops had reached full flowering as this is written, but will probably be doing so by the time you read this. There have been high levels of light leaf spot in crops this year, so that should also be considered as well as Sclerotinia at flowering. As oilseed rape prices are high, protecting yields will be very worthwhile.

Aviator (bixafen + prothioconazole) at 0.75 L/ha is a good choice with activity against both diseases and we’ve seen on average 0.25t/ha yield responses in farmer strip trials over standard treatments.

If flowering is prolonged a follow up treatment might be considered, but most growers will aim for one spray.

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