How to look after crops effectively this March in the south

Crop Progress

Cereals are continuing to look good as we reach the end of February. The cold spells have checked disease development, especially yellow rust and mildew in wheat. However, there is Septoria present on lots of varieties currently, which isn’t that unusual for the time of year. It’s easy to pick out some varieties in terms of growth stage or habit, especially Extase.

Oilseed rape on heavier soils have gone backwards over the past month, with heavy frosts and the cold winter causing quite a lot of die back in older leaves. Saying that, however, the potential for oilseed rape is all in the tap root and these temperatures warm up, it should have enough energy to get up and go.

There’s also been reports of cabbage stem flea beetle larvae. In some plants you can find them in the stems, but there is a train of thought that with the heavy frosts and older leaves dropping off, maybe they won’t have made it from the leaf into the stem.

To counter the poorer looking crops of oilseed rape, those on more free-draining soils in the east of the region ae looking much better, and we know there is potential.

Some spring barley has been drilled in good soil conditions, albeit with no rain in the past 30 days in Hampshire. As much as 70% of the spring barley area on some farms might have already been drilled.

Fertiliser applications have also begun across the region.

Richard’s agronomy tips for March

1. Prioritise grassweed herbicide applications

Most residual herbicide programmes in the autumn where applied have worked well and require little clean up this spring. Those that have had grassweeds come through have made the most of February conditions and targeted grassweeds while they are still small. To what effect? Time will tell.

If conditions have remained mild and there is still active growth then applying contact herbicides as soon as possible is recommended. Remember to always apply to a dry or drying leaf and make the most of clear blue sky days when maximum UV light it take up by the plant – we’ve seen incidental benefits in this conditions.

Product choice and timing could depend on what grassweed you are targeting. Certainly for some brome species which can be later germinating, make sure you’re targeting your application at the right time to not miss all of those later germinating weeds.

Understanding what you’re dealing with is half the battle and that’s also the case for resistance status. Testing will help with knowing what chemistry and what part of the rotation can be used to get on top of any issues, but be careful not to apply a resistance test from one field to all populations across the farm.

Bayer has done a number of studies where we’ve looked at a field with resistance, and then tested a neighbouring field. Over 50% of the time the neighbouring field is still susceptible to the active that has resistance issues on the other field.

Conducting multiple resistance tests over various fields over a number of years will help build a better picture over the farm.

2. Tackle yellow rust at T0 in winter wheat

Towards the end of March some wheat crops may be reaching their first fungicide application timing – try to ensure the gap between T0 and T1 does not exceed three to four weeks.

Currently yellow rust pressure is low, but this is likely a major driver of whether to apply a T0 of tebuconazole and / or a strobilurin fungicide around GS30.

Looking at our CropCheck results, which tests for latent Septoria disease, over recent seasons there appears to be an increase in Septoria levels on leaf four since the loss of chlorothalonil. That could be just incidental because we’ve had the weather patterns to promote it, but it could also be because of the loss of CTL and mean there is potentially a case of using folpet at T0 for the suppression of Septoria before your T1 fungicide.

3. Protect tillers in winter barley

In winter barley yield is driven by the number of viable ears / sqm at harvest and therefore tiller retention is crucial. Early season diseases, such as mildew, Rhynchosporium and net blotch can encourage the plant to abort tillers and to lose yield potential.

If there’s decent levels of infection of any of these in March that need to be treated before T1 at GS30/31, there’s the option to clean up with a prothioconazole-containing product.

Ascra (bixafen + fluopyram + prothioconazole) has become a really good fit at T1, which could be late March into early April. As well as providing excellent disease control, especially against net blotch, it also helps promote chlorophyll, nitrogen use efficiency and abiotic stress relief.

An alternative option at T1 is Siltra (bixafen + prothioconazole), which has been proven to deliver excellent disease control over many years of its use.

4. Maintain focus on light leaf spot in oilseed rape

Oilseed rape crops that have made it through the winter will be moving shortly into stem extension. The focus should be on maintaining light leaf spot control and possibly on growth regulation in some crops.

Our Spotcheck results in January has shown light leaf spot is increasing in incidence, with more positive cases down the east side of the country. It’s a disease that easier to control preventatively, otherwise you’re looking to suppress the disease in existing leaves.

During stem extension an application of prothioconazole, with or without tebuconazole, which will provide some growth regulation, will give you light leaf spot protection through to flowering.

5. Consider Velum Prime for spraing control in potatoes

In the south east potatoes will start to be planted when soil temperatures start to lift. Potato cyst nematodes, fortunately, tend not to be much of an issue in this region because of wide rotations and the availability of clean land.

However, free-living nematode can be a problem. Our liquid nematicide Velum Prime (fluopyram) has a label claim for the reduction of spraing, which is caused by tobacco rattle virus transmitted by free-living nematodes.

Before using Velum it is important to consider all other factors, such as field history, rotation risk and variety choice. Irrigation regimes and conditions at planting can also make a difference – potatoes are more at risk when they are drilled into cooler soils which remain cold and wet – more likely earlier in the planting window.

Velum can be used to achieve a reduction in spraing symptoms and for population management. You have two options for application – either broadcast spray onto the ridges and then incorporate by rotavating to a depth of 10-20cm, or apply in-furrow at planting.