South: Tackling light leaf spot with OSR stem extension spray

Spring barley is drilled-up on all but our heaviest land now thanks to the very welcome cold, dry spell. It took quite a bit of work to get the crop into the best conditions, patience being the essential ingredient.

With soil temperatures staying so low, we’ve yet to any signs of the crop. But most went in well, was effectively rolled and had pre-ems where needed. So all it wants now is a little warmth and, dare I say it, a decent drink.

Both of which would also be very welcome for our winter wheat ahead of T0.  The cold, lack of rain and constant wind has left a lot of stressed crops out there; crops which need the chance to pick-up some of the nitrogen we applied 2-3 weeks ago before we add to their stress with spring spraying.

Thankfully, both crop and disease development have been held back nicely by the weather, giving us the time. As well as actively-growing crops, we want leaf 4 well out before we spray and it’s still tightly rolled in most cases. While there’s plenty of septoria lurking – along with rust and mildew in many crops – there’s now no pressing need for early curative action either.

With leaf 5 staying fairly clean, we’re looking to a combination of azoles and multi-site protectants at T0 – which is still a week away – to keep leaf 4 in equally good health. And early April rather than late March treatment will give us the best possible leeway to keep the gap to our T1s in late April down to the three weeks we always prefer.

This year our T0s are going to be as much about balancing-up crops and their rooting as managing disease; especially since soils that slumped over the wet winter have gone so hard in the dry.  Our priorities here are a good low temperature active plant growth regulator, phosphite where root growth has been badly restricted by waterlogging and strategic micro-nutrients – zinc, in particular, for its value in encouraging nitrogen uptake.

Light leaf spot has become easy to find across our winter oilseed rape, which means we’ll be giving it a robust prothioconazole or prochloraz/tebuconazole treatment in our stem extension spray – still also around a week away in most cases, courtesy of the cold March. Having regulated themselves so well over the past three weeks, what we won’t be giving the majority of our crops, though, is anything much more than tebuconazole as a PGR.

To this we’ll be adding key trace elements – especially magnesium and boron – and a pyrethroid wherever necessary. Pollen beetles have been noticeable by their absence so far. However, we know populations can explode very damagingly ahead of flowering in the right conditions. And we don’t want them to get in the way of the excellent potential we have in some very nicely-structured, well-branched crops with flower buds down to the base and few signs of bolting.

See more