Vicki Brooks Blog: Black-grass battle lines well and truly drawn

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July 1, 2016

Vicki Brooks Blog: Black-grass battle lines well and truly drawn

Summer is the time when the full extent of black-grass becomes all too visibly apparent to everyone.  And this year is proving more stressful than ever in this respect.

Even where we achieved good autumn pre-em activity, crops are nowhere near as clean as they should be. There’s black-grass where we’ve never seen it before – on light land as well as heavy clay. Despite the very mild early winter, the plants didn’t get any bigger than normal. But unlike our crops which hit the buffers in the cold March, the black-grass kept on tillering away. So, by the time it was warm enough to apply the spring spray couldn’t touch it.

Our spring crops, though, are remarkably clean. There’s very little black-grass even in problem fields. This and the breadth of my colleagues’ long-term research at the Stow Longa black-grass technology centre underlines just how important first class cultural control has become.

Among the many practical options my growers and I have been taking away from Stow Longa this season, proper ploughing, delayed drilling and spring cropping are most popular – often in combination.

Not everyone has the capacity to plough or land which can reliably be drilled well into October, of course. However, with Mulika wheat and Explorer barley (on contract to Budweiser) both well-suited to heavy land and offering valuable premiums, I can’t think of anyone with significant black-grass concerns not now thinking of a spring cereal in their rotation; especially as so many of the fields we coded amber in our traffic light system for managing the weed last autumn now looking decidedly red.

Crop values are, unsurprisingly, an important driver for this change – not least to avoid a level of autumn herbicide use they simply cannot sustain. On the bright side, though, at today’s harvest prices there’s been far less reluctance than usual to spray-off badly-affected areas of winter cropping. This will make a very valuable contribution to minimising seed return.

Black-grass concerns apart, I have to say most of our winter and spring crops are looking remarkably promising as they go into mid-June. The 25-30 mm of rain we had over the first two days of the month here in the driest part of the UK have done them a world of good.

So far we’ve managed to keep Septoria confined to Leaf 2 on the wheats and we’re only seeing yellow rust in any spray misses.

With Septoria the biggest threat in the warm, wet weather it loves, we’ve continued to keep our foliar disease defences up as well as protecting the ears with combinations of prothioconazole and tebuconazole or prochloraz and tebuconazole at T3. As feed wheat marketability is crucial in an over-supplied world, we haven’t just been confining this to our quality wheats either.

Prothioconazole and spiroxamine, with or without trifloxystrobin, have been our T2 priorities for  spring barley which is looking nice and thick as its awns appear. The early mildew having dried-up well, rynchosporium was, as ever, our key target.

Since OSR flowering wasn’t as extended as we feared it might be, most crops only needed a single sclerotinia spray. From here on, like our other crops, what they now need is the right combination of sunshine and moisture to deliver on the potential they so clearly have. And we need enough patience with our desiccation timing to capture this potential and avoid red seeds.