West: Septoria levels remain worryingly high

In my last report it was my opinion that unless we had a prolonged dry spell, we were on the verge of experiencing the worst septoria epidemic for a long time. Thankfully since last writing, a prolonged dry spell is exactly what we have experienced. Even so, septoria levels remain worryingly high in some crops.

There are clear differences beginning to emerge between varieties, reflecting their resistance ratings. Resistance is not however the whole story when it comes to septoria. Some varieties can have a good resistance to the disease, but a poor tolerance to it, meaning that even relatively low levels of the disease can cause major yield loss. Other varieties may have a poorer resistance, but a better tolerance to the disease, meaning they might have a lot of symptoms, but yield loss turns out to be less than expected.

Most crops, even with well-timed T0 and T1 fungicide applications, are showing some symptoms on final leaf four. With septoria this far up in the crop at this stage of the seas on, a major outbreak of the disease is still on the cards if we have a return to wet conditions.

At the time of writing wet conditions are what we are experiencing in the lead up to T2 applications. If we are to keep on top of septoria we are going to need well-timed and robust doses at T2. The most forward crops I have seen are racing through the growth stages at the moment and are between GS37 and 39, meaning that they should be receiving their T2 applications imminently. Most crops are on target to be at this stage around the 15 May.

Winter barley crops continue to look promising and the rhynchosporium has cleaned up nicely following T1 fungicide applications. There is, however, the odd field of KWS Cassia that is showing small foci of very aggressive uncontrolled rhynchosporium. In the past this has always been an indicator that the plant’s natural resistance is on the verge of breaking down completely. For this reason alone I shall be nervous about recommending growers to continue with this variety beyond this season, particularly as there are alternatives that are equally as reliable, but with a better disease resistance.

Apologies to those growers who farm in drier climes for banging on at length about diseases, but in the Southwest these wet weather diseases represent a constantly clear and present danger, both to crop yield and quality.

Oilseed rape crops are well into the second half of their flowering period. Rape is notoriously difficult to read as a crop in terms of where the final yield might be, but generally canopies are close to optimum. Pest damage has been minimal and disease thus far has been well controlled. Therefore all the indicators are that crop yield should be good, but only time will tell. I hope that by actually writing that sentence I haven’t put the “kiss of death” on the crop.

With the dry spell, maize plantings are well ahead of the norm for the time of year. It remains to be seen whether this earlier planting has been the correct thing to do, as soil temperatures have not been particularly stable and we have been experiencing quite a few frosty nights. I suspect all will be fine if the current milder and damper weather stays with us for a while.

See more