North: The science behind finding the right fungicide timing

Rain at last! Words we always wonder if it is wise to say; as this usually heralds non-stop rain of biblical proportions. But on the whole crops look well and expectations are still optimistic for harvest. At this point some of you may wish to stop reading, as I outline the reasons not to be cheerful!

Wheat crops have just received their T1 sprays although timings range from leaf three barely visible to leaf two poking out. We all attend our winter meetings read the press and diligently decide on T0, T1, T2, and T3 as the chosen way forward. All is great until the British weather pattern hits and timings merge, split, reconvene and then depart again. Science is put on hold and practicality is applied. As we approach the countdown to flag leaf this is the final chance to catch late germinating weeds and a final scouting is vital to locate these areas. Growth regulation is also at the last chance saloon and again fields with weak strawed varieties or highly fertile soils should be prioritised. The disease threat is large and T2 will be dominated by SDHI chemistry and the inclusion or exclusion of Chlorothalonil will be the debating factor.

Winter barley crops will be receiving their final fungicide in the next few days after the awns have emerged. Product choice will be dictated by availability. Prothioconazole will be the core product of choice, but may not be available for all. Ramularia will be covered either by a suitable SDHI or some Chlorothalonil. Late growth regulators were applied earlier on the majority of crops allowing flexibility in applying the fungicide later.

Winter oilseed rape crops have limped into full flower and are due their mid-flower sclerotinia spray, which like the barley crop will be dictated by product availability. Seed weevil is always a conundrum at this time, made more complicated by the random nature of its presence. I have some crops alive with them and others completely absent. Due to the later timing fields to be treated will have a pyrethroid, subject to suitable bee notification and spray timing.

Winter beans are approaching the first chocolate spot timing and with the shortage of chlorothalonil based products, and the limited number of cleared products, this could lead to some difficulties. Spring beans are now emerging and some pea and bean weevil notching has started which need to be monitored and treated as required.

The remaining spring drilled crops are coming through, but not all uniformly. The most advanced spring barleys will be receiving a broad spectrum sulphonylurea. The welcome rains will help ensure that the later drilled fields emerge in their entirety and hopefully grow on well.


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