South: Sclerotinia key disease in oilseed rape

The small amount of rain that fell in March has been welcome. It helped get our spring-drilled crops off to a decent start as well as allowing our winter crops to green up nicely from their early nitrogen dressings.


The early mildew threat is thankfully subsiding with cereals growing away well from high levels of infection. However, the recent rain is keeping septoria tritici at the forefront of our minds, with denser crops at particular risk from spores splashed up from the lower leaves. Recent dewy nights and coolish days are ideal yellow rust conditions. So, even though we have yet to see a problem, we are keeping our eyes firmly peeled and our protection levels up.


With a good triazole plus chorothalonil T0 base, we are moving into our T1 spraying as Leaf 3 emerges with growing confidence. Septoria will be our main focus here, with Helix (prothioconazole + spiroxamine) our first choice to combat and guard against the rust and mildew threat as well. Our second wheats, which are thickening out well from their extra early nitrogen, will get a higher rate to counter eyespot and help fusarium control.


We will be taking the T1 opportunity to reinforce our earlier wheat plant growth regulator treatment and top up with key trace elements, like copper and manganese, for the greatest crop health and productivity, as well us tidying up later emerging cleavers. I am a firm believer in robust plant growth regulation and will be using a combination of Moddus (trinexapac-ethyl) and chlormequat in the form of Adjust for its extra crop safening value.

Last month’s rain gave our oilseed rape a welcome boost too. Crops have been taking advantage of their early nitrogen to move on well, with Excalibur and Castille starting to flower freely and the majority of other varieties not far behind. The pollen beetle threat has now subsided,  but we still keep checking backward crops.


Thinner crops that got particularly badly mauled by the pigeons are well behind and will remain so all season. Those that established robustly and came through the winter well, though, are looking good for the ideal 3.5 Green Area Index at flowering.


Sclerotinia is our key disease concern in rape, so we will be treating all crops with a boscalid-based spray at mid-flowering. We will consider a second spray if flowering is extended for a further two to three weeks, especially with the price of rape as it stands.

We’ll look to any later spray to give us valuable extra activity against alternaria, which can be a serious threat to thick crops if weather conditions turn wet. This could also be a good time to add any extra foliar urea, which can help boost yields particularly if the dry weather continues.






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