East Anglian agronomy insights for August

Autumn and spring vigour important for OSR varieties

Oilseed rape remains a viable crop for growers that are successfully establishing it – although I recognise that is easier said than done.

Variety plays a role in successful establishment but try to choose a variety suited to your intended drilling date. Earlier planting will be attractive to some who prefer to have a crop established before the peak cabbage stem flea beetle migration, which tends to be in the middle of August, even if those crops could take more management subsequently.

Pick varieties with good autumn vigour, especially if you’re going to delay until after peak migration, while also take a note of spring vigour to help with recovery from pest pressures coming out of winter.

As I write moisture doesn’t look like a limiting factor for drilling date, but always assess conditions when planning to drill, as moisture, as we all know, is critical.

Maximise post-harvest, pre-drilling weed control

With potentially a later harvest, higher weed seed return in the current season, and many growers understandably considering drilling earlier after a couple of difficult autumns, maximising weed control in what might be a shorter period between harvest and drilling will be critical.

Arguably if it was dry, post-harvest cultivations would give little benefit, but that doesn’t look like it will be the case this summer. In most cases, a shallow cultivation with a set of tines of discs, or use of a straw rake to encourage a flush of weeds will be useful.

But it is important to not just have a one-size fits all approach as management needs to be tailored for what weeds are present. The prime example for where an alternative approach is required is for meadow, soft or rye brome. These seeds need leaving on the surface for around a month to ripen before they will germinate.

When spraying off germinated weed seedlings, attention to detail with applications is crucial – this is probably the most important weed control spray of the season – but all too often it can be rushed.

Assess what is an appropriate rate for the weed size – if grassweeds are tillering you’ll need a higher rate for example, water volumes, whether a water conditioner is required, nozzle choice – a medium-coarse droplet is ideal, and forward speeds. If you have survivors, don’t carry out a repeat application without a cultivation in between.

Is there a case for pre-harvest glyphosate?

Higher weed burdens, unevenly established crops and potentially a catchy harvest are all reasons to at least consider whether a pre-harvest glyphosate in cereals could be worthwhile this season.

Remember it cannot be used on seed crops or malting barley, and there’s crop specific harvest intervals to adhere to.

If you’re using it for weed control, make sure you get a good desiccation of the weed – be mindful of infestation levels, growth stages and weed species when you’re thinking about rates, while remaining within maximum permitted rates.

Timing is important – don’t go too early and reduce crop quality or yield inadvertently.

Early disease reports in sugar beet require attention

First reports of rust in sugar beet were made in mid-July via the BBRO bulletin and in-field feedback, so hopefully growers will have made first applications of fungicides by the time you read this where crops were drilled in a timely manner.

It’s really important to have a strong start to a programme as you don’t want that pressure to build through the season.

There are some new options available to sugar beet growers this season, including Twist (trifloxystrobin). Trifloxystrobin was one-half of the previous market leading fungicide Escolta (cyproconazole + trifloxystrobin), and will be a more-than-useful addition to an azole-based fungicide, such as mefentrifluconazole, to bolster rust control.

In trials we have seen yield increases of 2-5 t/ha from its use.

As well as the traditional beet diseases of rust and powdery mildew, keep an eye out for Cercospora during August. Early treatment is vital once identified.

High blight pressure lingering

High blight pressure from the beginning of the season is lingering, which is no surprise given the weather. Risk in July has remained high with growers sticking to seven-day intervals as a minimum, with some opting for five days with appropriate actives where necessary.

Providing you haven’t reached the total dose of 6.4 L/ha for the season, Infinito (propamocarb + fluopicolide) remains a strong option for blight control. Ideally you would save one application for late in the season to take advantage of its activity against zoospores and tuber blight.

Continue to be mindful of alternating modes of action, although that can get tricky towards the end of the season when restrictions on total dose or numbers of applications can reduce options.

Remember if you still have maleic hydrazide applications to complete in August, apply these separately to blight fungicides as it has systemic action, and you don’t want anything to compromise its efficacy.

Treat cover crops as a cash crop

Cover crop popularity is increasing with Sustainable Farming Incentive payments playing a part. While it is not directly a cash crop in the traditional sense, it still needs to be treated with care and attention, so you achieve a viable cover crop and meet the objectives you have set out to achieve.

There’s little point in drilling it and hoping for the best – it needs managing. As with a cash crop, ideally you want a clean start, especially if it is being grown over winter, to avoid creating weed problems in following crops, while moisture is critical to good establishment, as with oilseed rape.