Well the cold weather came and went. In fact, over a 10 day period, we went from -16C to 17C. It certainly knocked the disease levels back, but didn’t really slow the growth of most crops with the exception perhaps of oilseed rape. Many wheat crops have already had a growth regulator and will get another one with a T0 fungicide any time from now on.
Although the cold weather checked the disease there is still enough rust about to justify a robust triazole dose at T0, plus or minus a mildewicide if necessary. The low rainfall levels so far have reduced the septoria risk, but I will still put in some chlorothalonil as it is such a reliable protectant. With shifting sensitivity of septoria to triazoles, I believe a multi-way approach to control is essential.
Winter oilseed rape is just about to take off and will be receiving a stem-extension (green – yellow bud) fungicide, using a highly active growth regulating triazole (probably tebuconazole) in mixture with carbendazim while we can still use it. It’s refreshing to learn that these triazoles have a relatively wide window of application to get very similar levels of growth regulation.
From early stem extension to yellow bud, there will be good PGR effect so in the absence of other diseases the later application will help to kickstart the sclerotinia and alternaria control. Reports of late light leaf spot are coming in, but I have to say I haven’t seen an awful lot.
Spring drilling is racing ahead in ideal conditions with spring barley nearly finished and spring beans and peas well advanced. I still say don’t rush in with spring oilseed rape and linseed yet – I once heard a saying ” the mad March hare turns into an April Fool” with these crops.