Scotland: Agronomy advice for the busy month of May

Crop Progress

As we approached the last 10 days of April, crops were growing, albeit slowly. Most were behind in growth stage where you would expect because of the wet and cold weather, as were growers with land work.

Most T0 fungicides in wheat had been missed, and while oilseed rape was shooting forwards, helped by the odd sunny warmer day, most crops were only just starting to flower.

Some spring barley crops were coming through the ground.

Potato planting was also behind with growers targeting lighter soils for fields to be destoned and ridged up before planting.

Edward’s agronomy tips for May

Robust sprays needed for remaining T1 fungicides in wheat

With T0s mostly missed, and disease including yellow rust, mildew and Septoria already in crops, any remaining T1 fungicides in May will likely need to be robust.

Most wheat varieties in Scotland tend to be susceptible to disease, and what is in the ground was mostly relatively early sown as once the weather closed in there have been precious few opportunities for further plantings.

That will increase the risk of Septoria as will the wet spring. In some cases, disease is already evident, but there will likely be latent infections that aren’t visible yet. Controlling these at T1 will be important, which pushes product choice to something like our Iblon-containing Vimoy® (isoflucypram) + Proline® (prothioconazole) fungicide.

Alternatively if you are growing a more-Septoria resistant variety or managed to get some later drilled wheat in the ground, then Ascra® (bixafen + fluopyram + prothioconazole) could be a good option especially if budgets are stretched.

Monitor May weather ahead of flag leaf sprays

Towards the end of May flag leaf emergence in wheat crops will trigger T2 sprays. Variety and drilling date will have helped set the disease risk in the crop, with weather the other key factor.

Monitor May weather to help judge risk. If it has remained wet during May you know that Septoria will have been splashed up the crop onto emerging leaves, whereas a dry spell will reduce risk. The other factor to consider is what you’ve sprayed at T1.

If it has been relatively dry during May and risk is reduced, then Ascra following a Vimoy® T1 could be an option, while if you chose Ascra or a competitor product at T1, then Vimoy® either with Proline® or in combination with our fenpicoxamid-containing product Jessico One® could be used. The latter will suit higher disease pressure situations – in trials it has offered around 0.3t/ha higher yields than using Univoq® (fenpicoxamid + prothioconazole).

All of the Bayer fungicides that have Leafshield technology on the label will have improved rainfastness, quickly drying on the leaf after spraying. That could be important in a catchy weather type year.

Consider disease risks in winter barley

Similarly to wheat, monitor winter barley crops in the period after T1 leading up to awns emerging T2 sprays. I’ve seen bits of mildew, Rhynchosporium and net blotch in winter barley crops driven by the wet weather, so make sure you have good control of those diseases from your T1 spray.

Keep an eye on timing as once the weather does warm the crop will rush through growth stages to catch up, so it is important to keep walking fields and making sure you don’t miss the awns emergence timing for T2.

The other disease to consider is Ramularia. If you haven’t used Ascra at T1, then it is a good choice to control Ramularia with the activity from fluopyram.

Otherwise, Siltra® (bixafen + prothioconazole) remains a good option at T2, although it might be worth adding folpet where there is Ramularia concern.

Use two spray fungicide programmes in spring barley

There’s going to be a lot of spring barley in Scotland, and more generally across the UK, this spring, so the end market is likely to be competitive. If you’re chasing malting barley premiums you’re looking to ensure your barley is better quality than others, which is why I’d recommend a two-spray disease control programme.

In spring barley, unlike winter barley, the second spray is usually the more important and will give the bigger return on investment, so I would start the programme at end of tillering with Siltra® at 0.4 L/ha. That will help control Rhynchosporium and net blotch, and then about three weeks later at flag leaf to awns emerging, use Ascra to help control Ramularia.

Check rotation for Sclerotinia risk in oilseed rape

Where first flowering sprays in oilseed rape haven’t already been applied, they’re likely to imminent in early May. Check rotational history for your oilseed rape fields for all the other crops that have Sclerotinia risks, such as veg crops, peas and beans, carrots, potatoes, etc., to help judge risk and also use the monitoring tools.

If you’re planning to use just one spray, then Aviator® (bixafen + prothioconazole) at 0.75 L/ha is a decent option. Many crops though, especially with variable growth, might end up with prolonged flowering and require a second spray around three weeks after the initial application to protect from Sclerotinia. If you plan that, then two sprays of 0.5 L/ha of Aviator® can be used.

Aviator is a also formulated with Leafshield technology, which will help the spray spread over the waxy leaves of oilseed rape, as well as making it rainfast quickly.

Watch out for fast emerging potato crops

With delayed potato planting, a lot of seed will be coming out of dormancy and going into warming soils. Once potato planting gets going, emergence is likely to very quick and will need monitoring, especially where using pre-emergence herbicides.

Emerger® (aclonifen) and Artist® (flufenacet + metribuzin) are a really good combination for weed control in potatoes, but Emerger® does need applying at least seven days before crop emergence.

With earlier plantings on potatoes that usually isn’t too much of a problem as it can take 3-4 weeks for emergence after planting, but these late April / early May plantings might emerge in just two weeks, so just keep an eye on that.

I’d let the ridges settle after planting for a few days, and then apply the pre-emergence as soon as possible after that.

Acknowledgements

Ascra contains bixafen + prothioconazole + fluopyram. iblon contains isoflucypram. Revystar contains mefentrifluconazole + fluxapyroxad. Univoq contains fenpicoxamid + prothioconazole. Elatus Era contains benzovindiflupyr + prothioconazole. Vimoy containts isoflucypram. Siltra contains bixafen + prothioconazole. Aviator contains bixafen + prothioconazole. Ascra, Iblon, Vimoy, Siltra are registered trademarks of Bayer. All other brand names used are Trademarks of other manufacturers in which proprietary rights may exist.

Use plant protection products safely. Always read the label and product information before use. Pay attention to the risk indications and follow the safety precautions on the label. For further information, including contact details, visit www.cropscience.bayer.co.uk or call 0808 1969522